Slide surface construction and process for producing the same

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a slide surface construction and particularly, to a slide surface construction formed of an aggregate of metal crystals and a process for producing the same.
2. Description of the Related Art
There are conventionally known slide surface constructions. Typical examples of such known slide surface constructions are: 1) a Pb alloy plated layer provided on the inner peripheral surface of a rolled-steel back plate of a slide bearing for an internal combustion engine, which is opposed to a rotary shaft, for the purpose of enhancing the seizure resistance; 2) various plated layers provided on an inner peripheral surface of a cylinder sleeve made of a cast iron in a combination of a piston made of an aluminum alloy and such cylinder sleeve in an internal combustion engine for the purpose of enhancing the slide characteristic; and 3) an Fe-plated layer provided on outer peripheral surfaces of a land portion and a skirt portion of a piston body made of an aluminum alloy in a piston for an internal combustion engine for purpose of enhancing the wear resistance.
However, the above known slide surface constructions suffer from a problem that under existing circumstances where speed and output of the internal combustion engine have tended to increase, the known slide surface construction is not sufficient in oil retaining property, namely, oil retention and poor in seizure resistance due to a relatively smooth slide surface thereof.
There is also a conventionally known slide surface construction which is formed on an engagement surface of a gear in a gearing device by roughening the engagement surface by machining or the like, and then applying a solid lubricating agent such as molybdenum disulfide, graphite and the like, or a semi-solid lubricating agent such as grease onto the roughened engagement surface, so that latter retains the lubricating agent.
However, the known engagement surface is simple in view of microstructure and has a problem that it is low in solid lubricating agent retention and the like and, as a result, is poor in seizure resistance under a high load condition.
Therefore, the present assignee has previously developed a slide surface construction which is formed on an inner peripheral surface of a backing plate, an inner peripheral surface of a cylinder sleeve, an outer peripheral surface of a piston body, an engagement surface of a gear and the like, and which includes a large number of pyramid-shaped metal crystals in the slide surface thereof (see Japanese Patent Application Laid-open No.174089/94).
If the slide surface construction is formed in the above manner, adjacent pyramid-shaped metal crystals assume mutually biting states and hence, the slide surface takes on an intricate aspect comprising a large number of fine crests, a large number of fine valleys formed between the crests, and a large number of swamps formed due to the mutual biting of the crests. Therefore, the slide surface construction is improved in oil retention and in solid lubricating agent retention and the like and thus, has an enhanced seizure resistance.
In the above-described slide bearing, however, the following situation has been encountered: when two regions suitable under different sliding conditions are produced in the slide surface construction, even if one of the two regions exhibits a good sliding characteristic under a severe sliding environment, it cannot be expected that the other region exhibits such a good sliding characteristic, because the slide characteristic of the slide surface construction is substantially constant over the entire region thereof.
As for the gearing device, it has been ascertained that in order to accommodate the severe sliding environment, for example, where a sudden and excessively large variation in load occurs in the gear, it is necessary to further enhance the solid lubricating agent retention of the slide surface construction.
As for the cylinder sleeve, it has been ascertained that when the viscosity of the oil is high, for example, at a lower temperature, the flow of the oil lacks a smoothness, resulting in a relatively high dynamic friction coefficient .mu. and for this reason, the friction loss tends to be increased.
Further, as for the piston, it has been also ascertained that in order to accommodate the severe sliding environment, it is necessary to further enhance the oil retention of the slide surface construction to reduce the solid contact to the utmost, thereby further enhancing the seizure resistance, and to reduce the dynamic friction coefficient .mu. to further enhance the wear resistance.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a slide surface construction of the above-described type, wherein it is possible for two regions suitable under different sliding conditions to exhibit excellent sliding characteristics, respectively.
To achieve the above object, according to the present invention, there is provided a slide surface construction formed of an aggregate of metal crystals, comprising first and second regions suitable under different sliding conditions, the first region including (2hhh) oriented metal crystals existing therein, which have a body-centered cubic structure with their (2hhh) planes (by Miller indices) oriented toward a slide surface, the content S.sub.2hhh of the (2hhh) oriented metal crystals being set in a range of 20%.ltoreq.S.sub.2hhh .ltoreq.100%, and the second region including (hhh) oriented metal crystals existing therein, which have a body-centered cubic structure with their (hhh) planes (by Miller indices) oriented toward a slide surface, the content S.sub.hhh of the (hhh) oriented metal crystals being set in a range of 40%.ltoreq.S.sub.hhh .ltoreq.100%.
In the first region, the (2hhh) oriented metal crystals are grown into a columnar shape, with their tip ends being formed of fish-shaped metal crystals such as sardine-shaped metal crystals in the slide surface. If the content of the (2hhh) oriented metal crystals is set in the above-described range, the slide surface takes on a very intricate aspect due to the large number of fish-shaped metal crystals existing in the slide surface and therefore, it has a good oil retention. Moreover, the (2hhh) planes of the (2hhh) oriented metal crystals form a secondary slide surface and hence, they have a high hardness and a high strength.
The second region is most suitable for use in a site of a severe sliding condition.
On the other hand, in the second region, the (hhh) oriented metal crystals are grown into a columnar shape, with their tip ends being formed of hexagonal or trigonal pyramid-shaped metal crystals in the slide surface. If the content of the (hhh) oriented metal crystals is set in the above-described range, the slide surface takes on a very intricate aspect due to the large number of hexagonal or trigonal pyramid-shaped metal crystals existing in the slide surface and therefore, it has a good oil retention. However, the (hhh) oriented metal crystals has a low hardness, as compared with the (2hhh) oriented metal crystals.
The first region is most suitable for use in a site of a sliding condition in which a seizure resistance is preferentially required and which is more moderate than that of the first region.
In this way, according to the present invention, it is possible to provide a slide surface construction in which the two region suitable under different sliding conditions can exhibit excellent slide characteristics, respectively by the fact that the slide surface construction has a specified structure as described above.
However, if the content S.sub.2hhh is lower than 20%, or if the content S.sub.hhh is lower than 40%, the above-described function and effect cannot be provided.
It is another object of the present invention to provide a slide surface construction of the above-described type, which has a further enhance retention to the slide lubricating agent and the like.
To achieve the above object, according to the present invention, there is provided a slide surface construction formed of an aggregate of metal crystals, wherein the area rate A of pyramid-shaped metal crystals in a slide surface is in a range of 40%.ltoreq.A.ltoreq.100%, at least some of the pyramid-shaped metal crystals being heteromorphic pyramid-shaped metal crystals having at least one notched recess in at least one ridgeline section, the pseudo-area rate B of the heteromorphic pyramid-shaped metal crystals in the slide surface being in a range of 20%.ltoreq.B.ltoreq.100%.
If the area rate A of pyramid-shaped metal crystals in a slide surface is set in the above-described range, the adjacent pyramid-shaped metal crystals assume mutually biting states and hence, the slide surface takes on an intricate aspect comprising a large number of fine crests, a large number of fine valleys formed between the crests, and a large number of fine swamps formed due to the mutual biting of the crests. Thus, the slide surface construction exhibits a good retention to the slide and semi-solid lubricating agents. Moreover, since the pseudo-area rate B of the different pyramid-shaped metal crystals is set in the above-described range, the notched recess in the metal crystal exhibits an anchoring effect to the solid and semi-solid lubricating agents, thereby doubling the retention.
In the slide surface construction, even if it is placed in a severe sliding environment, the lubricant retention of the slide surface construction is maintained at a high degree under lubrication, while the dispersion of a sliding load is provided by the large number of fine pyramid-shaped metal crystals under non-lubrication. Thus, the slide surface construction exhibits an excellent seizure resistance both under lubrication and under non-lubrication.
In this way, according to the present invention, it is possible to provide a slide surface construction which has a good retention of the solid and semi-solid lubricating agents and exhibits an excellent sliding characteristic under a severe sliding environment, for example, where a sudden and excessively large variation in load occurs, by the fact that the slide surface construction has a specified structure as described above.
However, if the area rate A of the pyramid-shaped metal crystals is lower than 40%, the slide surface tends to be simplified and hence, such a range is not desirable. If the pseudo-area rate B of the different pyramid-shaped metal crystals is lower than 20%, the anchoring effect cannot be expected.
It is a further object of the present invention to provide a process for producing a slide surface construction of the above-described type, which is capable of producing a slide surface construction having a further enhanced retention to the solid lubricating agent and the like.
To achieve the above object, according to the present invention, there is provided a process for producing a slide surface construction formed of an aggregate of metal crystals by an electrolytic plating treatment utilizing a pulse current process, wherein the electrolytic plating treatment is divided into a plurality of steps, an energization stopping step being interposed between a step of the last time and a step of the current time, the time T.sub.2 required for the energization stopping step and the minimum electric current maintaining time T.sub.1 in the step of the last time being in a relationship of T.sub.2 .gtoreq.100 T.sub.1, and the average cathode electric-current density CD.sub.2 in the step of the current time and the average cathode electric-current density CD.sub.1 in the step of the last time being in a relationship of CD.sub.2 .gtoreq.1.2 CD.sub.1.
With the above producing process, a slide surface construction including pyramid-shaped metal crystals and different pyramid-shaped metal crystals in the slide surface can be easily mass-produced. However, if T.sub.2 <100 T.sub.1, or if CD.sub.2 <1.2 CD.sub.1, the pseudo-area rate. B of the different pyramid-shaped metal crystals is lower than 20%.
Further, it is another object of the present invention to provide a slide surface construction of the above-described type, wherein the friction loss can be reduced even when the oil has a high density.
To achieve the above object, according to the present invention, there is provided a slide surface construction formed of an aggregate of metal crystals, wherein the area rate A of rounded pyramid-shaped metal crystals in a slide surface is in a range of 40%.ltoreq.A.ltoreq.100%, each of the rounded pyramid-shaped metal crystals having a ridgeline which assumes a convex arcuate shape, a slope-correspondence area (which means an area corresponding to a slope) being defined between the adjacent ridgelines and comprising two band-like regions each of which is one of slopes forming each ridgeline, and a V groove-like region connected to the two band-like regions, the opening width of the V groove-like region being gradually reduced from a skirt portion toward an apex.
If the area rate A of the rounded pyramid-shaped metal crystals is set in such range, the adjacent rounded pyramid-shaped metal crystals assumes mutually biting states. Therefore, the slide surface takes on an intricate aspect comprising a large number of fine crests, a large number of fine valleys formed between the crests, and a large number of fine swamps formed due to the mutual biting of the crests.
In this case, if each of the ridgelines of the pyramid-shaped metal crystal is rectilinear and the apex of the pyramid-shaped metal crystal is pointed, and if the slope-correspondence area between the adjacent ridgelines is formed into a relatively deep V shape such that the opening width is gradually reduced from the skirt potion toward the apex, namely, if the pyramid-shaped metal crystal is angular, the following problem is encountered: when the viscosity of an oil is high at a low temperature, the flow of the oil lacks a smoothness, because the angular pyramid-shaped metal crystals perform an occluding effect.
In contrast, if the rounded pyramid-shaped metal crystals as described above exist in the slide surface, the flow resistance of the oil having a high viscosity is reduced on the slide surface and therefore, it is possible for the oil to flow smoothly. Thus, it is possible to reduce the shear resistance of an oil film formed on the slide surface reduce the friction loss.
Since the slide surface takes on the intricate aspect, as described above, the slide surface construction has a good oil retention, substantially irrespective of the viscosity of the oil. Thus, the slide surface construction exhibits an excellent seizure resistance, even if it is placed in a severe sliding environment. On the other hand, even under non-lubrication, the dispersion of a sliding load is provided by the large number of fine rounded pyramid-shaped metal crystals and hence, the seizure resistance of the slide surface construction is relatively good.
If the area rate A of the rounded pyramid-shaped metal crystals is lower than 40%, the slide surface tends to be simplified and hence, such an area rate A lower than 40% is undesirable.
It is a yet further object of the present invention to provide a slide surface construction of the above-described type, wherein the seizure resistance can be further enhanced and the dynamic friction coefficient .mu. can be lowered to further enhance the wear resistance by further enhancing the oil retention to reduce the solid contact to the utmost.
To achieve the above object, according to the present invention, there is provided a slide surface construction formed of an aggregate of metal crystals, comprising a large number of truncated hexagonal pyramid-shaped metal crystals in a slide surface, the area rate A of the truncated hexagonal pyramid-shaped metal crystals being in a range of 40%.ltoreq.A.ltoreq.100%, a top face of each of the truncated hexagonal pyramid-shaped metal crystals comprising a plurality of flat face portions, with a step provided between adjacent ones of the flat face portions.
If the area rate A of the truncated hexagonal pyramidshaped metal crystals in the slide surface is set in such range, a complicated valley extending at random is defined by the adjacent truncated hexagonal pyramid-shaped metal crystals and therefore, the slide surface takes on an intricate aspect. Moreover, the intricateness is doubled by the fact that the top face of each truncated hexagonal pyramid-shaped metal crystal comprises the plurality of flat face portions and the step is provided between the adjacent flat face portions. As a result, the flow resistance of the oil on the slide surface is remarkably increased.
Thus, it is possible to remarkably enhance the oil retention of the slide surface construction and hence, even in a severe sliding environment, the solid contact can be reduced to the utmost, causing the slide surface construction to exhibit an excellent seizure resistance. In addition, since the top face has the flat face portions, the dynamic friction coefficient .mu. can be lowered, causing the slide surface construction to exhibit an excellent wear resistance in the severe sliding environment.
Yet further, it is an object of the present invention to provide a process for producing a slide surface construction of the above-described type, by which the slide surface construction can be mass-produced.
To achieve the above object, according to the present invention, there is provided a process for producing a slide surface construction, comprising: a step for forming a deposit layer including a large number of pyramid-shaped metal crystals in a surface serving as a slide surface and having an area rate A of the pyramid-shaped metal crystals in the surface in a range of 40%.ltoreq.A.ltoreq.100%; a step for subjecting a surface of the deposit layer to a polishing to form the pyramid-shaped metal crystals into truncated pyramid-shaped metal crystals; and a step for subjecting the surface of the polished deposit layer to an etching to divide a top face of each of the truncated pyramid-shaped metal crystals into a plurality of flat face portions and to provide a step between the adjacent flat face portions.
With the above producing process, a slide surface construction as described above can be mass-produced.
The above and other objects, features and advantages of the following detailed description of preferred embodiments taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a front view of a connecting rod including a slide bearing;
FIG. 2 is an enlarged view of a portion indicated by the arrow 2 in FIG. 1;
FIG. 3 is a developed view of a semi-annular half of the slide bearing;
FIG. 4 is an enlarged sectional view taken along a line 4--4 in FIG. 3;
FIG. 5 is a perspective view showing a body-centered cubic (bcc) structure and its (hhh) plane and (2hhh) plane;
FIG. 6 is a plan view of a trigonal pyramid-shaped metal crystal;
FIG. 7 is a diagram showing the inclination of the (2hhh) plane in the body-centered cubic structure;
FIG. 8 is a diagram showing the inclination of the (hhh) plane in the body-centered cubic structure;
FIG. 9 is a graph of a waveform of an output from a power source for electrolytic plating;
FIG. 10 is a diagram illustrating how X-ray is applied to the slide surface;
FIG. 11 is an X-ray diffraction pattern for an example 1a of a first region of a slide surface;
FIG. 12 is an X-ray diffraction pattern for an example 4a of the first region of a slide surface;
FIG. 13 is a photomicrograph showing the crystal structure of the slide surface of the example 1a;
FIG. 14 is a photomicrograph showing the crystal structure of the slide surface of the example 4a;
FIG. 15 is a photomicrograph showing the crystal structure of the slide surface of an example 8a;
FIG. 16 is a graph illustrating the relationship between the content S.sub.211 of {211} oriented Fe crystals and the seizure generating load;
FIG. 17 is a graph illustrating the relationship between the content S.sub.211 of {211} oriented Fe crystals and the wear resistance;
FIG. 18 is an X-ray diffraction pattern for an example 1b of a second region of a slide surface;
FIG. 19 is an X-ray diffraction pattern for an example 5b of the second region of a slide surface;
FIG. 20 is a photomicrograph showing the crystal structure of the slide surface of the example 1b;
FIG. 21 is a photomicrograph showing the crystal structure of the slide surface of the example 5b;
FIG. 22 is a graph illustrating the relationship between the content S.sub.222 of {222} oriented Fe crystals and the seizure generating load;
FIG. 23A is a front view of a piston;
FIG. 23B is a view take along an arrow 23B in FIG. 23A;
FIG. 24 is a graph illustrating the relationship between the content S.sub.211 of {211} oriented Fe crystals and the seizure generating load;
FIG. 25 is a sectional view of an essential portion of a gearing device;
FIG. 26 is an enlarged view of a portion indicated by an arrow 26 in FIG. 25;
FIG. 27 is a view taken in the direction of an arrow 27 in FIG. 26;
FIG. 28A is a perspective view of a heteromorphic hexagonal pyramid-shaped metal crystal;
FIG. 28B is a perspective view of a normal hexagonal pyramid-shaped metal crystal;
FIG. 29 is a graph of a waveform of an output from an electrolytic plating power source;
FIG. 30 is an X-ray diffraction pattern for an example 1;
FIG. 31 is an X-ray diffraction pattern for an example 11;
FIG. 32 is an X-ray diffraction pattern for an example 15;
FIG. 33A is a photomicrograph showing the crystal structure of the slide surface of the example 1;
FIG. 33B is a photomicrograph showing the crystal structure of a vertical section of the example 1;
FIG. 33C is an enlarged photomicrograph of an essential portion shown in FIG. 33B;
FIG. 34 is a photomicrograph showing the crystal structure of the slide surface of the example 11;
FIG. 35 is a photomicrograph showing the crystal structure of the slide surface of the example 15;
FIG. 36 is a graph illustrating the relationship between the area rate A of hexagonal pyramid-shaped Fe crystals and the seizure generating load;
FIG. 37 is a graph illustrating the relationship between the area rate A of hexagonal pyramid-shaped Fe crystals and the dynamic friction coefficient .mu.;
FIG. 38 is a graph illustrating the relationship between the average cathode current density in a second step and the pseudo-area rate B of heteromorphic hexagonal pyramid-shaped Fe crystals;
FIG. 39 is a partial vertical sectional view of an essential portion of a cylinder block including a piston;
FIG. 40 an enlarged view of a portion indicated by an arrow 40 in FIG. 39;
FIG. 41 is a view taken in the direction of the arrow 41 in FIG. 40;
FIG. 42A is a perspective view of a rounded hexagonal pyramid-shaped metal crystal;
FIG. 42B is a plan view of the rounded hexagonal pyramid-shaped metal crystal;
FIG. 43 is a perspective view of an angular hexagonal pyramid-shaped metal crystal;
FIG. 44 is a broken-away perspective view of a round bar having a slide surface construction;
FIG. 45 is an X-ray diffraction pattern for an example 1 of the slide surface construction;
FIG. 46 is an X-ray diffraction pattern for an example 4 of the slide surface construction;
FIG. 47 is an X-ray diffraction pattern for an example 8 of the slide surface construction;
FIG. 48A is a photomicrograph showing the crystal structure of the slide surface of the example 1;
FIG. 48B is an enlarged photomicrograph taken from FIG. 48A;
FIG. 48C is an enlarged photomicrograph taken from FIG. 48B;
FIG. 49 is a photomicrograph showing the crystal structure of the slide surface of an example 3;
FIG. 50 is a photomicrograph showing the crystal structure of the slide surface of an example 4;
FIG. 51 is a photomicrograph showing the crystal structure of the slide surface of an example 8;
FIG. 52 is a view for illustrating how a dynamic friction coefficient .mu. is measured;
FIG. 53 is a graph illustrating the relationship between the area rate A of rounded and angular hexagonal pyramid-shaped Fe crystals and the dynamic friction coefficient .mu.;
FIG. 54 is a graph illustrating the seizure generating loads for the examples 1 to 8;
FIG. 55 is a front view of an essential portion of a piston with a portion broken away;
FIG. 56 is an enlarged sectional view taken along a line 56--56 in FIG. 55;
FIG. 57 is a view taken in the direction of the arrow 57 in FIG. 56;
FIG. 58A is a plan view of truncated hexagonal pyramid-shaped metal crystals;
FIG. 58B is an enlarged sectional view taken along a line 58B--58B in FIG. 58A;
FIG. 59 is a sectional view similar to FIG. 56, but showing a deposit layer;
FIG. 60 is a view taken in the direction of the arrow 60 in FIG. 59;
FIG. 61 is a side view similar to FIG. 57, but showing a deposit layer after being polished;
FIG. 62 is an X-ray diffraction pattern for an example 1a of the deposit layer;
FIG. 63 is a photomicrograph showing the crystal structure of a surface of the example 1a of the deposit layer;
FIG. 64 is a photomicrograph showing the crystal structure of a surface of an example 3a of the deposit layer;
FIG. 65 is a photomicrograph showing the crystal structure of a surface of an example 1b of a deposit layer after being polished;
FIG. 66A is a photomicrograph showing the crystal structure of a slide surface in an example 1a of a slide surface construction;
FIG. 66B is a tracing of FIG. 66A;
FIG. 67 is a graph illustrating the relationship between the area rate A of hexagonal pyramid-shaped Fe crystals and the seizure generating load; and
FIG. 68 is a graph illustrating the relationship between the area rate A of hexagonal pyramid-shaped Fe crystals and the dynamic friction coefficient .mu..

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIRST EMBODIMENT
Referring to FIG. 1, a slide bearing 5 is disposed between a larger end hole 2 in a connecting rod 1 for an internal combustion engine and a crankpin 4 of a crankshaft 3. The slide surface bearing 5 is formed of a pair of semi-annular halves 6 which have the same structure.
As shown in FIG. 2, in a backing plate 7 of each of the semi-annular halves 6, a lamellar slide surface construction 9 is formed on an inner peripheral surface opposed to the crankpin 4 by plating.
FIG. 3 shows the developed semi-annular half 6 as flat. The slide surface construction 9 includes a pair of narrow band-shaped first regions R.sub.1 extending over the entire length of opposite ends in an axial direction "a" of the crankpin, and a wider band-shaped second region R.sub.2 located between the two first regions R.sub.1. The first regions R.sub.1 are placed under a sliding condition more severe than that under which the second region R.sub.2 is placed, due to the flexing of the crankpin 4. As shown in FIGS. 2 and 3, an oil hole 10 is defined in a central portion of the semi-annular half 6. A chamfer 11 is provided in a portion of the oil hole 10 adjacent the slide surface construction 9.
As best shown in FIGS. 3 and 4, the slide surface construction 9 is formed of an aggregate of metal crystals. Preferably (2hhh) oriented metal crystals 13 having a body-centered cubic (bcc) structure as shown in FIG. 5 with their (2hhh) planes (by Miller indices) oriented toward a slide surface 12 exist in the first region R.sub.1. The content (which indicates a presence or existing amount) S2.sub.hhh of the (2hhh) oriented metal crystals is set in a range of 20%.ltoreq.S2.sub.hhh .ltoreq.100% in the first region R.sub.1. The lower limit value of the content S2.sub.hhh is preferably equal to 25%.
Preferably (hhh) oriented metal crystals 14 having a body-centered cubic structure as shown in FIG. 5 with their (hhh) planes (by Miller indices) oriented toward a slide surface 12 exist in the second region R.sub.2. The content (which indicates a presence or existing amount) S.sub.hhh of the (hhh) oriented metal crystals is set in a range of 40%.ltoreq.S.sub.hhh .ltoreq.100% in the second region R.sub.2.
In the first region R.sub.1, the (2hhh) oriented metal crystals 13 are grown into a columnar shape from the inner peripheral surface 8 of the backing plate 7, with tip ends of the (2hhh) oriented metal crystals 13 being formed of fish-shaped metal crystals 15 such as sardine-shaped metal crystals in the slide surface 12. If the content S2.sub.hhh of the (2hhh) oriented metal crystals 13 is set in the above-described range, the slide surface 12 takes on a very intricate aspect due to the large number of fish-shaped metal crystals existing in the slide surface 12, and hence, has a good oil retention. Moreover, the (2hhh) planes of the (2hhh) oriented metal crystals 13 are secondary slide faces and for this reason, the crystals 13 have a high hardness and a high strength.
Such first region R.sub.1 has excellent seizure and wear resistances and therefore, even if the sliding condition is severe, the first region R.sub.1 can withstand such severe sliding condition.
In the second region R.sub.2, the (hhh) oriented metal crystals 14 are grown into a columnar shape from the inner peripheral surface of the backing plate 7, with tip ends of the (hhh) oriented metal crystals 14 being formed of hexagonal pyramid-shaped metal crystals 16 as clearly shown in FIG. 3, or trigonal pyramid-shaped metal crystals 17 as clearly shown in FIG. 6, in the slide surface 12. If the content S.sub.hhh of the (hhh) oriented metal crystals 14 is set in the above-described range, the slide surface 12 takes on a very intricate aspect due to the large number of hexagonal pyramid-shaped metal crystals 16 and/or the large number of trigonal pyramid-shaped metal crystals 17 existing in the slide surface 12, and hence, has a good oil retention. However, the (hhh) oriented metal crystals 14 have a lower hardness, as compared with the (2hhh) oriented metal crystals 13.
Such second region R.sub.2 has an excellent seizure resistance and hence, is most suitable for use in a site where the seizure resistance is preferentially required.
As clearly shown in FIG. 7, the inclination of the (2hhh) plane with respect to a phantom plane 18 along the slide surface 12 appears as the inclination of the fish-shaped metal crystal 15 and hence, an influence is imparted to the oil retention and wear resistance of the first region R.sub.1. The inclination angle .theta. formed by the (2hhh) plane with respect to the phantom plane 18 preferably is set in a range of 0.degree..ltoreq..theta..ltoreq.15.degree.. In this case, the direction of inclination of the (2hhh) plane is not limited. If the inclination angle .theta. is larger than 15.degree., the oil retention and the wear resistance of the first region R.sub.1 are reduced. The preferred inclination angle also applies to the (hhh) plane, as shown in FIG. 8.
Examples of the metal crystals having the bcc structure are those of simple metals such as Fe, Cr, Mo, W, Ta, Zr, Nb, V and the like, or those of alloys thereof.
In the plating treatment for forming the first and second regions R.sub.1 and R.sub.2 of the slide surface construction, the range of conditions for a plating bath in carrying out an electrolytic Fe plating are as shown in Table 1. In this case, when one of the regions is formed, a portion corresponding to the other region, or the other region is masked.
TABLE 1______________________________________ Plating bath FerrousSlide surface sulfate Temperatureconstruction (g/liter) pH (.degree.C.)______________________________________First and second 100-400 5-7 40-60regions______________________________________
The adjustment of pH is carried out using ammonia water.
A pulse current process is mainly utilized as an energizing method. In the pulse current process, the electric current I from a plating power source is controlled to describe a pulse waveform with the passage of time T, so that the current I is increased from a minimum current value Imin and reaches a maximum current value Imax, and is then dropped to the minimum current value Imin, as shown in FIG. 9. In FIG. 9, T.sub.ON is an energization time from the start of the increase of the electric and current and T.sub.C is a cycle time, wherein one cycle is defined as being from the start of an earlier increase to the start of a subsequent increase.
TABLE 2______________________________________ Pulse current processSlide surface CDmax CDm T.sub.ONconstruction (A/dm.sup.2) (A/dm.sup.2) T.sub.ON /T.sub.C (msec)______________________________________First and second .gtoreq.2.2 .gtoreq.1.0 .ltoreq.0.45 .ltoreq.100regions______________________________________
Table 2 shows the minimum or maximum conditions for carrying out the pulse current process. In Table 2, CDmax represents a maximum cathode current density; CDm represents an average cathode current density; and T.sub.ON /T.sub.C represents a ratio of the energization time T.sub.ON to the cycle time T.sub.C, i.e., a time ratio.
If the pulse current process is utilized, the ion concentration in the vicinity of a cathode is uniformized due to the fact that the maximum electric current alternately flows and does not flow in the plating bath. Thus, the composition of the first and second regions R.sub.1 and R.sub.2 can be stabilized.
In the above-described electrolytic Fe plating process, the precipitation and content of the (2hhh) oriented Fe crystals or the (hhh) oriented Fe crystals are controlled by changing the plating bath conditions and the energizing conditions, as described below. This control is easy under the utilization of the pulse current process and hence, the slide surface 12 is easily formed into an intended form.
In addition to the electrolytic Fe plating, other examples of a plating process are a PVD process, a CVD process, a sputtering process, an ion plating and the like, which are gas-phase plating processes.
Example-1
(a) Sliding Characteristic of First Region R.sub.1
For each test example, a backing plate 7 made of a rolled sheet steel (JIS SPCC) and having an outside diameter of 51 mm (52.3 mm in a free state), a width of 19.5 mm, a thickness of 1.485 mm and an oil hole 10 diameter of 3 mm was prepared. Those portions of the inner peripheral surface 8 of the backing plate 7 which correspond to the two first regions R.sub.1 were subjected to an electrolytic Fe plating to form first regions R.sub.1 formed of an aggregate of Fe crystals and having a width of 2 mm and a thickness of 15 .mu.m. During this time, that portion of the backing plate 7 which corresponds to the second region R.sub.2 was masked using a steel sheet as a conductive jig.
Then, the two first regions R.sub.1 were masked in the same manner as that described above, and that portion of the backing plate 7 which corresponds to the second region R.sub.2 was subjected to the electrolytic Fe plating to form a second region R.sub.2 having a thickness of 15 .mu.m.
Table 3 shows the electrolytic Fe plating conditions for examples 1a to 5a of the first regions, and Table 4 shows electrolytic Fe plating conditions for examples 6a to 9a of the first regions and an example 1b of the second region. The plating time was varied within a range of 5 to 60 minutes in order to set the thickness for the examples 1a to 9a and 1b at 15 .mu.m, as described above.
TABLE 3__________________________________________________________________________Plating bathFerrous Pulse current processFirst sulfate Temperature CDmax CDmregion (g/liter) pH (.degree. C.) (A/dm.sup.2) (A/dm.sup.2) T.sub.ON /T.sub.C T.sub.ON (msec)__________________________________________________________________________Example 1a 400 6.5 41.5 40 8 0.2 2Example 2a 400 6.5 41.5 30 6 0.2 2Example 3a 400 6.3 41.5 25 5 0.2 2Example 4a 400 6.5 43 30 6 0.2 2Example 5a 400 6.3 43 25 5 0.2 2__________________________________________________________________________
TABLE 4__________________________________________________________________________ Plating bath Ferrous Pulse current process sulfate Temperature CDmax CDm T.sub.ON (g/liter) pH (.degree. C.) (A/dm.sup.2) (A/dm.sup.2) T.sub.ON /T.sub.C (msec)__________________________________________________________________________First regionExample 6a 400 6.3 45 25 5 0.2 2Example 7a 400 6.2 48 25 5 0.2 2Example 8a 400 6.1 48 25 5 0.2 2Example 9a 400 6 48 25 5 0.2 2Second regionExample 1b 400 6 48 25 5 0.2 2__________________________________________________________________________
Tables 5 and 6 show the crystal form of the slide surface, the content of the oriented Fe crystals and the hardness of a section of the slide surface construction for the examples, with Table 5 corresponding to the examples 1a to 5a, and Table 6 corresponding to the examples 6a to 9a and 1b.
TABLE 5__________________________________________________________________________First Crystal form of slide Content S (%) of oriented Fe crystals Hardnessregion surface S.sub.110 S.sub.200 S.sub.211 S.sub.310 S.sub.222 HmV__________________________________________________________________________Example 1a Fish-shaped 5.4 0.9 91.3 0 2.4 675Example 2a Fish-shaped 15.2 7.9 52.7 8.6 15.6 634Example 3a Fish-shaped and granular 20.8 15 25.7 16.4 22.1 584Example 4a Fish-shaped and hexagonal 1 0 47.9 0 51.1 581 pyramid-shapedExample 5a Fish-shaped and hexagonal 14.8 3.3 25.9 3.6 52.4 579 pyramid-shaped__________________________________________________________________________
TABLE 6__________________________________________________________________________ Crystal form of slide Content S (%) of oriented Fe crystals Hardness surface S.sub.110 S.sub.200 S.sub.211 S.sub.310 S.sub.222 HmV__________________________________________________________________________First regionExample 6a Fish-shaped and 0 0 25.2 0 74.8 523 hexagonal pyramid-shapedExample 7a Fish-shaped and 0.1 0 20.6 0 79.3 491 hexagonal pyramid-shapedExample 8a Hexagonal pyramid-shaped 0 0 19.5 0 80.5 475 and granularExample 9a Hexagonal pyramid-shaped 0.5 0 1.4 0 98.1 420Second regionExample 1b Hexagonal pyramid-shaped 0.5 0 1.4 0 98.1 420__________________________________________________________________________
The content of the oriented Fe crystals was determined using equations which will be described below, based on the X-ray diffraction patterns for the examples 1a to 9a and 1b. As shown in FIG. 10, the X-ray diffraction was carried out at a 0.degree. position where X-ray was applied at right angles to the slide surface 12, and a position where the slide surface 12 was inclined at an inclination angle .alpha., taking the inclination of the fish-shaped metal crystals and the like into consideration. In this case, .alpha. was set at 5.degree., 10.degree. and 15.degree.. The result of measurement at the 0.degree. position and the result of measurement at the 5.degree., 10.degree. and 15.degree. position are substantially identical to each other and hence, the X-ray diffraction pattern at the 0.degree. position was used for the calculation of the content. FIGS. 11 and 12 show the X-ray diffraction patterns for the examples 1a and 4a at the 0.degree. position. In the following equations, for example, the {110} oriented Fe crystal means an oriented Fe crystal with its {110} plane oriented toward the slide surface.
{110} oriented Fe crystals: S.sub.110 ={(I.sub.110 /IA.sub.110)/T}.times.100
{200} oriented Fe crystals: S.sub.200 ={(I.sub.200 /IA.sub.200)/T}.times.100
{211} oriented Fe crystals: S.sub.211 ={(I.sub.211 /IA.sub.211)/T}.times.100
{310} oriented Fe crystals: S.sub.310 ={(I.sub.310 /IA.sub.310)/T}.times.100
{222} oriented Fe crystals: S.sub.222 ={(I.sub.222 /IA.sub.222)/T}.times.100
wherein each of I.sub.110, I.sub.200, I.sub.211, I.sub.310 and I.sub.222 is a measurement (cps) of an intensity of X-ray reflected from each crystal plane; each of IA.sub.110, IA.sub.200, IA.sub.211, IA.sub.310 and IA.sub.222 is an intensity ratio of X-rays reflected from crystal planes in an ASTM card, IA.sub.110 =100; IA.sub.200 =20, IA.sub.211 =30; IA.sub.310 =12; and IA.sub.222 =6. Further, T=(I.sub.110 /IA.sub.110)+(I.sub.200 /IA.sub.200)+(I.sub.211 /IA.sub.211)+(I.sub.310 /IA.sub.310)+(I.sub.222 /IA.sub.222).
FIG. 13 is a photomicrograph showing the crystal structure of the slide surface in the example 1a. In FIG. 13, a large number of fish-shaped Fe crystals are observed. The fish-shaped Fe crystal is a {211} oriented Fe crystal with its {211} plane oriented toward the slide surface. The content S.sub.211 (S2.sub.hhh) of the {211} oriented Fe crystals is equal to 91.3%, as shown in Table 5 and FIG. 11.
FIG. 14 is a photomicrograph showing the crystal structure of the slide surface in the example 4a. In FIG. 14, a large number of fish-shaped Fe crystals and a large number of hexagonal pyramid-shaped Fe crystals are observed. The fish-shaped Fe crystal is a {211} oriented Fe crystal with its {211} plane oriented toward the slide surface. The content S.sub.211 of the {211} oriented Fe crystals is equal to 47.9%, as shown in Table 5 and FIG. 12. The hexagonal pyramid-shaped Fe crystal is a {222} oriented Fe crystal with its (hhh) plane, i.e., {222} plane oriented toward the slide surface. The content S.sub.222 (S.sub.hhh) of the {222} oriented Fe crystals is equal to 51.1%, as shown in Table 5 and FIG. 12.
FIG. 15 is a photomicrograph showing the crystal structure of the slide surface in the example 8a. In FIG. 15, a large number of hexagonal pyramid-shaped Fe crystals and a large number of granular Fe crystals are observed. The hexagonal pyramid-shaped Fe crystal is likewise a {222} oriented Fe crystal with its {222} plane oriented toward the slide surface. The content S.sub.222 of the {222} oriented Fe crystals is equal to 80.5%, as shown in Table 6.
In Tables 5 and 6, the examples 1a to 7a are high in hardness, as compared with the examples 8a, 9a and 1b. This is attributable to the content S.sub.211 of the {211} oriented Fe crystals being equal to or higher than 20%. In this case, if S.sub.211 .gtoreq.25%, the degree of increase in hardness is remarkable.
In order to carry out a seizure test, a rotary shaft made of a carbon steel (JIS S48C, a soft nitrided material) and having a diameter of 47.94 mm and a length of 140 mm was placed in a housing (with a clearance of 30 .mu.m) of a metal tester in such a manner that it was clamped by a pair of slide bearings of semi-annular halves having the construction of example 1a for the first region and 1b for the second region. Then, the seizure test was carried out under conditions of the number of rotations of the rotary shaft being equal to 6000 rpm and the amount of oil supplied being equal to 600 ml/min, and by a method for applying load to the slide bearings in such a manner that a load of 2,000 N was first applied to the slide bearings and maintained for 2 minutes, and after that, the load was increased in sequence by 2,000 N while maintaining it for 2 minutes each time the load was increased. During this time, the temperature of those portions of the backing plate of the slide bearing corresponding to the two first regions was measured, and the load at the time when the temperature exceeded 180.degree. C. was defined as a seizure generating load. A similar seizure test was carried out for the slide bearings each comprised of a pair of semi-annular halves having the construction of examples 2a to 9a in the first regions R.sub.1 and the example 1b in the second region R.sub.2.
Then, chips having the examples 1a to 9a were fabricated and subjected to a wear test in a chip-on-disk manner under lubrication to measure a wear amount. Conditions for the wear test are as follows: the material for the disk was a carbon steel (JIS S48C, a soft nitrided material); the peripheral speed of the disk was 12.5 m/sec; the amount of oil supplied was 5 ml/min; the area of the slide surface of the chip was 1 cm.sup.2 ; the urging load on the chip was 300 N; the sliding time was 30 minutes; and the wear amount was the difference between the thickness of the chip before the test and the thickness of the chip after the test.
Table 7 shows results of the seizure test and the wear test for the examples 1a to 9a along with the ratio S.sub.211 /S.sub.222 of the content S.sub.211 of the {211} oriented Fe crystals to the content S.sub.222 of the {222} oriented Fe crystals.
TABLE 7______________________________________ Seizure generating Wear amountFirst region Ratio S.sub.211 /S.sub.222 load (N) (.mu.m)______________________________________Example 1a 38.0 54000 1.0Example 2a 3.4 52000 1.2Example 3a 1.2 48000 1.5Example 4a 0.9 48000 1.9Example 5a 0.5 46500 2.0Example 6a 0.3 46000 2.2Example 7a 0.3 37500 3.5Example 8a 0.2 37000 3.7Example 9a 0.01 36000 3.7______________________________________
FIG. 16 shows the relationship between the content S.sub.211 of the {211} oriented Fe crystals and the seizure generating load for the examples 1a to 9a. In FIG. 16, points (1a) to (9a) correspond to the examples 1a to 9a, respectively. The relationship between the points and the examples applies to Figures which will be described hereinafter.
FIG. 17 shows the relationship between the content S.sub.211 of the {211} oriented Fe crystals and the wear amount for the examples 1a to 9a.
In FIGS. 16 and 17, the enhancement in seizure resistance and in wear resistance in examples 1a to 6a is distinct from the examples 7a, 8a and 9a. From this, it can be seen that the content S.sub.211 in the f irst region R.sub.1 may be set in a range of S.sub.211 .gtoreq.20%. Preferably, the content S.sub.211 is in a range of S.sub.211 .gtoreq.25%.
If the ratio S.sub.211 /S.sub.222 is set in a range of S.sub.211 /S.sub.222 .gtoreq.1 when the content S.sub.211 is equal to or higher than 25%, the seizure and wear resistances are enhanced remarkably, as in the examples 1a to 3a. In the case of the example 4a, the content S.sub.211 is relatively high, but the seizure resistance is equivalent to that of the example 3a having the relatively low content S.sub.211, and the wear resistance is equivalent to that of the example 5a having the relatively low content S.sub.211, because the ratio S.sub.211 /S.sub.222 is lower than 1.
(b) Sliding Characteristic of Second Region R.sub.2
For each test example, a backing plate 7 made of a rolled sheet steel (JIS SPCC) and having an outside diameter of 51 mm (52.3 mm in a free state), a width of 19.5 mm, a thickness of 1.485 mm and an oil hole diameter of 3 mm was prepared. That portion of the inner peripheral surface 8 of the backing plate 7 which corresponds to the second regions R.sub.2 was subjected to an electrolytic Fe plating to form a second region R.sub.2 formed of an aggregate of Fe crystals and having a width of 15.5 mm and a thickness of 15 .mu.m. During this time, those portions of the backing plate 7 which corresponds to the two first regions R.sub.1 were masked using a steel sheet as a conductive jig.
Then, the second region R.sub.2 was masked in the same manner as that described above, and those portions of the backing plate 7 which correspond to the two first regions R.sub.1 were subjected to the electrolytic Fe plating to form two first regions R.sub.1 having a thickness of 15 .mu.m.
Table 8 shows the electrolytic Fe plating conditions for examples 1b to 5b of the second region and an example 1a of the first regions R.sub.1. The plating time was varied within a range of 5 to 60 minutes in order to set the thickness for the examples 1b to 5b and 1a at 15 .mu.m, as described above.
TABLE 8__________________________________________________________________________ Plating bath Ferrous Pulse current process sulfate Temperature CDmax CDm T.sub.ON (g/liter) pH (.degree. C.) (A/dm.sup.2) (A/dm.sup.2) T.sub.ON /T.sub.C (msec)__________________________________________________________________________Second regionExample 1b 400 6 48 25 5 0.2 2Example 2b 300 6 48 17.5 3.5 0.2 2Example 3b 300 6 48 15 3 0.2 2Example 4b 400 4 50 20 4 0.2 2Example 5b 400 3 50 20 4 0.2 2First regions 400 6.5 41.5 40 8 0.2 2Example 1a__________________________________________________________________________
Table 9 shows the crystal form of the slide surface, the content of the oriented Fe crystals, and the hardness of a section of the slide surface construction for the examples 1b to 5b and 1a.
TABLE 9__________________________________________________________________________Crystal form of slide Content S (%) of oriented Fe crystals Hardnesssurface S.sub.110 S.sub.200 S.sub.211 S.sub.310 S.sub.222 HmV__________________________________________________________________________SecondregionExample 1b Hexagonal pyramid-shaped 0.5 0 1.4 0 98.1 420Example 2b Hexagonal pyramid- 11.3 3.8 22.2 2 60.7 384 shaped, Fish-shaped and granularExample 3b Hexagonal pyramid- 17.5 9.7 20.3 11.8 40.7 333 shaped, Fish-shaped and granularExample 4b Hexagonal pyramid-shaped 8.5 15 18.9 20.5 37.1 318 and granularExample 5b Granular 14.4 19.7 18.9 24.5 22.5 285First regions Fish-shaped 5.4 0.9 91.3 0 2.4 675Example 1a__________________________________________________________________________
The content of the oriented Fe crystals was determined in the same manner as that described above, based on the X-ray diffraction patterns for the examples 1b to 5b and 1a. FIG. 19 is an X-ray diffraction pattern at the 0.degree. position for the example 5b.
FIG. 20 is a photomicrograph showing the crystal structure of the slide surface in the example 1b. In FIG. 20, a large number of hexagonal pyramid-shaped Fe crystals are observed. The hexagonal pyramid-shaped Fe crystal is a {222} oriented Fe crystal with its (hhh) plane, i.e., {222} plane oriented toward the slide surface. The content S.sub.222 (S.sub.hhh) of the {222} oriented Fe crystals is equal to 98.1%, as shown in Table 9 and FIG. 18.
FIG. 21 is a photomicrograph showing the crystal structure of the slide surface in the example 5b. In FIG. 21, a large number of granular Fe crystals are observed. In this case, the content of the differently oriented Fe crystals is substantially averaged or equal, as shown Table 9 and FIG. 19.
Then, a seizure test was carried out under the same conditions as those described above, using a slide bearing comprised of a pair of semi-annular halves having the construction of the examples 1b and 1a for the second and first regions, respectively, and using the above-described metal tester. The measurement of the temperature corresponding to the seizure generating load was carried out for that portion of the outer peripheral surface of the backing plate of the slide bearing which corresponds to the second region. A similar seizure test was carried out using a slide bearing comprised of a pair of semi-annular halves having the construction of each of the examples 2b to 5b for the second region and 1a for the first region. Table 10 shows results of the seizure test.
TABLE 10______________________________________Second region Seizure generating load (N)______________________________________Example 1b 36000Example 2b 35000Example 3b 32000Example 4b 22000Example 5b 21000______________________________________
FIG. 22 shows the relationship between the content S.sub.222 of the {222} oriented Fe crystals and the seizure generating load for the examples 1b to 5b.
In FIG. 22, the enhancement in seizure resistance in examples 1b, 2b and 3b is distinct from the examples 4b and 5b. From this, it can be seen that the content S.sub.222 in the second region R.sub.2 may be set in a range of S.sub.222 .gtoreq.40%.
Example-2
A piston 19 for an internal combustion engine is shown in FIGS. 23A and 23B and is formed of an aluminum alloy (JIS AC8A, a T7-treated material). A lamellar slide surface construction 9 is formed on the entire outer peripheral surface of a land portion 20 of the piston 19 and on a portion of an outer peripheral surface of a skirt portion 21 of the piston 19.
In this case, the section located on the entire outer peripheral surface of the land portion 20 and the section located on a portion of the skirt portion 21 correspond to first regions R.sub.1 of the slide surface construction 9. The term "a portion" of the skirt portion 21 corresponds to the portion obtained by excluding the two recesses 23 around two piston pin holes 22 from the skirt portion 21, and two central portions 24 surrounded by a one-dot and dashed line between both the recesses 23. Sections located at the two central portions surrounded by the one-dot and dashed line correspond to second regions R.sub.2 of the slide surface construction 9.
Specifically, the sections of the piston 19 corresponding to the second regions R.sub.2 (namely, the two central portions) and the two recesses 23 were masked by the same means as that described above, and slide surface constructions of examples 1a to 9a of the first region R.sub.1 described in section (a) above were formed on the sections corresponding to the first regions R.sub.1 by an electrolytic Fe plating process under the same conditions as those described above. Then, the first regions R.sub.1 were masked by the same means as that described above, and a construction of above example 1b of the second region R.sub.2 described in section (a) above was formed at each of the two central portion 24 and the two recesses 23 by an electrolytic Fe plating process under the same conditions. In this case, the surface skins formed at the two recesses 23 and having hexagonal pyramid-shaped Fe crystals in a surface thereof have an oil accumulating function.
Then, chips having the examples 1a to 9a were fabricated and subjected to a seizure test in a chip-on-disk manner under lubrication to measure the seizure generating load, thereby providing results given in Table 11. Conditions for the seizure test were as follows: the material for the disk was a cast iron (JIS FC250); the peripheral speed of the disk was 12.5 m/sec; the amount oil supplied was 40 ml/min; the area of the slide surface of the chip was 1 cm.sup.2 ; the method for applying load to the chip was to apply a load of 20 N to the chip and maintain it for 2 minutes, and after that, the load was increased in sequence by 20 N while maintaining it for 2 minutes each time whenever the load was increased.
TABLE 11______________________________________First region Seizure generating load (N)______________________________________Example 1a 2750Example 2a 2680Example 3a 2450Example 4a 2420Example 5a 2380Example 6a 2350Example 7a 1500Example 8a 1480Example 9a 1450______________________________________
FIG. 24 shows the relationship between the content S.sub.211 of the {211} oriented Fe crystals and the seizure generating load for the examples 1a to 9a.
In FIG. 24, the enhancement in seizure resistance for examples 1a to 6a is distinct from the examples 7a to 9a. From this, it can be seen that the content S.sub.211 in the first region R.sub.1 may be set in a range of S.sub.211 .gtoreq.20%. Preferably, the content S.sub.211 is in a range of S.sub.211 .gtoreq.25%.
If the ratio S.sub.211 /S.sub.222 is set in a range of S.sub.211 /S.sub.222 .gtoreq.1 when the content S.sub.211 is equal to or higher than 25%, the seizure resistance is enhanced remarkably as in the examples 1a to 3a. In the case of the example 4a, the content S.sub.211 is relatively high, but the seizure resistance is equivalent to those of the examples 3a and 5a having the relatively low content S.sub.211, because the ratio S.sub.211 /S.sub.222 is lower than 1.
The first embodiment is not limited to the slide bearing and piston but is applicable to various slide members such as a balancer shaft, a cam shaft, a piston pin and the like, which have two regions of different sliding conditions.
SECOND EMBODIMENT
In a gearing device 25 shown in FIG. 25, two gears 26.sub.1 and 26.sub.2 meshed with each other are formed of a steel. A lamellar slide surface construction 9 is formed on a meshed face of at least one of the gears 26.sub.1 by an electrolytic plating treatment.
The slide surface construction 9 is formed of an aggregate of metal crystals having a body-centered cubic structure (which will be also referred to as a bcc structure hereinafter), as in the first embodiment, as shown in FIG. 5. The aggregate includes a large number of columnar crystals 28 grown from the meshed face 27, as shown in FIG. 26. Each of the columnar crystals 28 is at least one of a (hhh) oriented metal crystal with its (hhh) plane (by Miller indices) oriented toward a slide surface 12, and a (2hhh) oriented metal crystal with its (2hhh) plane (by Miller indices) oriented toward the slide surface 12.
When the columnar crystal 28 having the bcc structure as described above is the (hhh) oriented metal crystal with its (hhh) plane (by Miller indices) oriented toward the slide surface 12, the tip end of the columnar metal crystals can be formed into hexagonal pyramid-shaped metal crystals (pyramid-shaped metal crystals) 16 in the slide surface 12, as shown in FIG. 27. The hexagonal pyramid-shaped metal crystals 16 are small in average grain size and substantially uniform in grain size, as compared with trigonal pyramid-shaped metal crystals (pyramid-shaped metal crystals) which are likewise (hhh) oriented metal crystals. In the hexagonal pyramid-shaped metal crystals 16 and the like, the grain size and the height are in an interrelation to each other. Therefore, the grain sizes being substantially uniform, indicates that the heights are also substantially equal to one another.
As shown in FIGS. 26 and 28A, at least some of the hexagonal pyramid-shaped metal crystals 16 are heteromorphic hexagonal pyramid-shaped metal crystals (heteromorphic pyramid-shaped metal crystals) 16.sub.1. The heteromorphic hexagonal pyramid-shaped metal crystal 16.sub.1 has at least one notched recess 30 (one notched recess in the illustrated embodiment) in at least one ridgeline 29 (six ridgelines in the illustrated embodiment).
Normal hexagonal pyramid-shaped metal crystals 16.sub.2 having no notched recess 30 in the ridgeline 29 as clearly shown in FIGS. 26 and 28B are included in the hexagonal pyramid-shaped metal crystals 16.
The area rate A of the hexagonal pyramid-shaped metal crystals 16 such as the normal hexagonal and heteromorphic hexagonal pyramid-shaped metal crystals 16.sub.2 and 16.sub.1 in the slide surface 12 is set in a range of 40%.ltoreq.A.ltoreq.100%. The area rate A was determined according to an equation, A=(c/b).times.100(%), wherein b represents an area of the slide surface 12, and c represents an area occupied in the slide surface 12 by all the hexagonal pyramid-shaped metal crystals 16.
The pseudo-area rate B of the heteromorphic hexagonal pyramid-shaped metal crystals 16.sub.1 in the slide surface 12 is set in a range of 20%.ltoreq.B.ltoreq.100%. The pseudo-area rate B was determined in the following manner: as shown in FIG. 26, a reference line segment d having a predetermined length L.sub.1 in a direction perpendicular to the direction of growth of the columnar crystals 28 is defined to pass through or in the vicinity of the bottoms of the normal hexagonal and heteromorphic hexagonal pyramid-shaped metal crystals 16.sub.2 and 16.sub.1 in a vertical section of the slide surface construction 9. The length of the heteromorphic hexagonal pyramid-shaped metal crystals 16.sub.1 at or in the vicinity of their bottoms in the same direction as the lengthwise direction of the reference line segment d is defined as L.sub.2, and the sum of the lengths L.sub.2 of all the heteromorphic hexagonal pyramid-shaped metal crystals 16.sub.1 included within the reference line segment d is defined as nL.sub.2 (wherein n is the number of heteromorphic hexagonal pyramid-shaped metal crystals 16.sub.1, e.g., n=4 in the illustrated embodiment). Thus, the pseudo-area rate B was calculated according to an equation of B=nL.sub.2 /L.sub.1).times.100(%). A photomicrograph is used for this calculation. The reason why such a method is employed is that even if the slide surface 12 is observed from above by a microscope, the heteromorphic hexagonal pyramid-shaped metal crystals 16.sub.1 cannot be discriminated.
If the area rate A of the hexagonal pyramid-shaped metal crystals 16 in the slide surface 12 is set in the above-described range, adjacent ones of the hexagonal pyramid-shaped metal crystals 16 assume mutually biting states, as shown in FIG. 27. Thus, the slide surface 12 takes on a very intricate aspect comprising a large number of extremely fine crests 31, a large number of extremely fine valleys 32 formed between the crests 31, and a large number of extremely fine swamps 33 formed due to the mutual biting of the crests 31. Therefore, the slide surface 12 exhibits a good retention to solid and semi-solid lubricating agents. Moreover, because the pseudo-area rate B of the heteromorphic hexagonal pyramid-shaped metal crystals 16.sub.1 is set in the above-described range, the notched recesses 30 in the heteromorphic hexagonal pyramid-shaped metal crystals 16.sub.1 exhibit an anchoring effect to the solid and semi-solid lubricating agents, thereby doubling the retention.
In such slide surface construction 9, even if it is placed in a severe sliding environment, the lubrication agent retention of the slide surface construction 9 is maintained higher under lubrication, and the dispersion of a sliding load is provided under non-lubrication by the large number of fine hexagonal pyramid-shaped metal crystals 16. Thus, the slide surface construction 9 exhibits an excellent seizure resistance both under lubrication and under non-lubrication.
Further, as a result of uniform fine division of the hexagonal pyramid-shaped metal crystals 16, a local increase in surface pressure can be avoided, and a fine division of the sliding load can be achieved. Thus, the slide surface construction 9 exhibits an excellent wear resistance not only under lubrication but also under non-lubrication.
When the columnar crystals having the bcc structure are (2hhh) oriented metal crystals with their (2hhh) planes (by Miller indices) oriented toward the slide surface 12, tip ends of the columnar crystals can be formed into small pyramid-shaped metal crystals (pyramid-shaped metal crystals).
Even when the hexagonal and trigonal pyramid-shaped metal crystals and the small pyramid-shaped metal crystals exist in the slide surface, the area rate A of the pyramid-shaped metal crystals is likewise set in a range of 40%.ltoreq.A.ltoreq.100%. Again, when the hexagonal and trigonal pyramid-shaped metal crystals and the small pyramid-shaped metal crystals exist in the slide surface, the pseudo-area rate B of the heteromorphic pyramid-shaped metal crystals is likewise set in a range of 20%.ltoreq.B.ltoreq.100%.
As shown in FIG. 8, the inclination of the (hhh) plane with respect to the phantom plane 18 along the slide surface 18 appears as the inclination of the hexagonal pyramid-shaped metal crystals 16 and hence, an influence is imparted to the lubricant retention and the wear resistance of the slide surface construction 9. The inclination angle .theta. formed by the (hhh) plane with respect to the phantom plane 18 is set in a range of 0.degree..ltoreq..theta..ltoreq.15.degree., as in the first embodiment. In this case, the direction of inclination of the (hhh) plane is not limited. If the inclination angle .theta. is higher than 15.degree., the lubricant retention and the wear resistance of the slide surface construction 9 are reduced. The inclination .theta. also applies to the (2hhh) plane.
Examples of the metal crystals having the bcc structure are those of simple metals such as Fe, Cr, Mo, W, Ta, Zr, Nb, V and the like, or those of alloys thereof, as in the first embodiment.
In the electrolytic plating process for forming the slide surface construction 9, the conditions for a plating bath in carrying out an electrolytic Fe plating are as shown in Table 12.
TABLE 12______________________________________Plating bathFerrous sulfate(g/liter) pH Temperature (.degree.C.)______________________________________100-400 3-7 40-60______________________________________
The adjustment of pH of the plating bath is carried out using ammonia water.
The electrolytic Fe plating process is divided into a plurality of steps (two steps, in the embodiment). In the first and second steps, a pulse current process is utilized as an energizing method. In the pulse current process, electric current I from a plating power source is controlled to describe a pulse waveform with the passage of time T, so that the current I is increased from a minimum current value Imin (including Imin=0) and reaches a maximum current value Imax, and is then dropped to the minimum current value Imin, as shown in FIG. 29.
An energization stopping step for bringing the energizing electric current into zero is interposed between the first step (the proceeding step) and the second step (the succeeding step). A relationship, T.sub.2 .gtoreq.100 T.sub.1 is established between the time T.sub.2 required for the energization stopping step and the minimum electric current maintaining time T.sub.1 in the first step. In this case, the minimum electric current maintaining time T.sub.1 in the first step is set in a range of T.sub.1 .gtoreq.2.2 msec.
A relationship, CD.sub.2 .gtoreq.1.2 CD.sub.1 is established between the average cathode current density CD.sub.2 in the second step and the average cathode current density CD.sub.1 in the first step. In this case, the average cathode current density CD.sub.1 in the first step is set in a range of CD.sub.1 .gtoreq.2.2 A/dm.sup.2, and the maximum cathode current density CDmax in the first and second steps is set in a range of CDmax.gtoreq.2.6 A/dm.sup.2.
Further, if the energization time period from the start of the increasing of the electric current I to the start of the dropping is represented by T.sub.3, and a cycle time period is represented by T.sub.4 wherein one cycle is defined as being from the start of the proceeding increasing to the start succeeding increasing of the electric current, the ratio of the energization time period T.sub.3 to the cycle time period T.sub.4, i.e., the time ratio T.sub.3 /T.sub.4 is set in a range of T.sub.3 /T.sub.4 .ltoreq.0.45 in the first and second steps. If T.sub.3 /T.sub.4 >0.45, the area rate A of the pyramid-shaped Fe crystals in the slide surface may be lower than 40% in some cases, depending upon other conditions.
A slide surface construction having the above-described structure can be easily mass-produced by utilizing such electrolytic Fe plating process.
Example-1
As a simulation of a gear 26.sub.1, a slide surface construction 9 formed of an aggregate of Fe crystals and having a thickness of 15 .mu.m was formed by subjecting an outer periphery of one surface of a disk made of a chromemolybdenum steel (JIS SCM420, a carburized material) to an electrolytic Fe plating process comprising first and second steps or only a first step.
Table 13 shows the conditions for the plating bath for examples 1 to 15 of slide surface constructions, and Tables 14 and 15 show energizing conditions for the examples 1 to 15.
TABLE 13______________________________________ Plating bath FerrousSlide surface sulfate Temperatureconstruction (g/liter) pH (.degree.C.)______________________________________Example 1 400 6 55Example 2 300 6 55Example 3 250 5.5 55Example 4 400 6 50Example 5 400 6 50Example 6 300 6 50Example 7 250 5.5 50Example 8 400 6 50Example 9 300 6 50Example 10 250 5.5 50Example 11 400 6 50Example 12 300 6 50Example 13 250 5.5 50Example 14 200 4.5 50Example 15 200 3 50______________________________________
TABLE 14__________________________________________________________________________ EnergizationSlide First step stoppingsurface T.sub.3 T.sub.1 CDmax Plating step T.sub.2construction (msec) (msec) T.sub.3 /T.sub.4 CD.sub.1 (A/dm.sup.2) (A/dm.sup.2) time (min) (sec)__________________________________________________________________________Example 1 2 8 0.2 4 20 12 1 (125T.sub.1)Example 2 2 8 0.2 3.5 17.5 13.7Example 3 2 8 0. 2 3 15 16Example 4 2 8 0.2 4 20 12Example 5 2 8 0.2 4 20 12Example 6 2 8 0.2 3.5 17.5 13.7Example 7 2 8 0.2 3 15 16__________________________________________________________________________Slide Second stepsurface T.sub.3 T.sub.1 CDmax Platingconstruction (msec) (msec) T.sub.3 /T.sub.4 CD.sub.2 (A/dm.sup.2) (A/dm.sup.2) time (min)__________________________________________________________________________Example 1 1 19 0.05 7.2 (1.8 CD.sub.1) 144 1.7Example 2 1 19 0.05 6.3 (1.8 CD.sub.1) 126 1.9Example 3 1 9 0.1 5.4 (1.8 CD.sub.1) 54 2.2Example 4 1 9 0.1 5.2 (1.3 CD.sub.1) 52 2.3Example 5 2 8 0.2 4.8 (1.2 CD.sub.1) 24 2.5Example 6 2 8 0.2 4.2 (1.2 CD.sub.1) 21 2.9Example 7 2 8 0.2 3.6 (1.2 CD.sub.1) 18 3.3__________________________________________________________________________
TABLE 15__________________________________________________________________________ EnergizationSlide First step stoppingsurface T.sub.3 T.sub.1 CDmax Plating step T.sub.2construction (msec) (msec) T.sub.3 /T.sub.4 CD.sub.1 (A/dm.sup.2) (A/dm.sup.2) time (min) (sec)__________________________________________________________________________Example 8 2 8 0.2 4 20 12 1 (125T.sub.1)Example 9 2 8 0.2 3.5 17.5 13.7Example 10 2 8 0.2 3 15 16Example 11 2 8 0.2 4 20 15Example 12 2 8 0.2 3.5 17.5 17.1Example 13 2 8 0.2 3 15 20Example 14 2 8 0.2 3.5 17.5 17.1Example 15 2 8 0.2 0.5 2.5 120__________________________________________________________________________Slide Second stepsurface T.sub.3 T.sub.1 CDmax Platingconstruction (msec) (msec) T.sub.3 /T.sub.4 CD.sub.2 (A/dm.sup.2) (A/dm.sup.2) time (min)__________________________________________________________________________Example 8 3 7 0.3 4.4 (1.1 CD.sub.1) 14.7 2.7Example 9 3 7 0.3 3.9 (1.1 CD.sub.1) 13 3.1Example 10 3 7 0.3 3.3 (1.1 CD.sub.1) 11 3.6Example 11 -- -- -- -- -- --Example 12 -- -- -- -- -- --Example 13 -- -- -- -- -- --Example 14 -- -- -- -- -- --Example 15 -- -- -- -- -- --__________________________________________________________________________
Table 16 shows the content S of the oriented Fe crystals for the examples 1 to 15.
TABLE 16______________________________________Slidesurface Content S (%) of oriented Fe crystalsconstruction {110} {200} {211} {310} {222}______________________________________Example 1 0 0 3.8 0 96.2Example 2 7.1 2.8 20.1 1.1 68.9Example 3 19.3 4.6 33.8 2 40.3Example 4 0 0 3.2 0 96.8Example 5 0 0 2.7 0 97.3Example 6 6.6 2.5 18.3 0.5 72.1Example 7 18.7 5 34.1 0.7 41.5Example 8 0.3 0 4.5 0 95.2Example 9 6.1 3.1 19.4 1.2 70.2Example 10 19.5 4.9 33.1 1.7 40.8Example 11 0 0 3.5 0 96.5Example 12 6 3.9 17.6 2.6 69.9Example 13 21.8 3.5 30.8 2.4 41.5Example 14 19.4 12.4 19.7 13 35.5Example 15 33.6 16.5 17.5 17.7 14.7______________________________________
The content S was determined in the same manner as in the first embodiment, based on the X-ray diffraction patterns (X-ray was applied in a direction perpendicular to the slide surface) for the examples 1 to 15. FIG. 30 is the X-ray diffraction pattern for the example 1; FIG. 31 is the X-ray diffraction pattern for the example 11, and FIG. 32 is the X-ray diffraction pattern for the example 15.
Table 17 shows the crystal form of the slide surface, the area rate A and grain size of the hexagonal pyramid-shaped Fe crystals in the slide surface, the pseudo-area rate B of heteromorphic hexagonal pyramid-shaped Fe crystals, and the hardness of a vertical section of the slide surface construction.
TABLE 17__________________________________________________________________________ Pseudo-area rate B (%) of Hexagonal pyramid heteromorphicSlide shaped Fe crystals hexagonalSurface Crystal form of slide Area rate Grain size pyramid-shaped HardnessConstruction surface A (%) (.mu.m) Fe crystals HmV__________________________________________________________________________Example 1 hexagonal pyramid-shaped 100 2.5 100 405Example 2 hexagonal pyramid- 70 2.7 72.4 381 shaped, small pyramid- shaped and granularExample 3 hexagonal pyramid-shaped 40 3.3 41.1 293 and granularExample 4 hexagonal pyramid-shaped 100 2.5 40.8 398Example 5 hexagonal pyramid-shaped 100 2.5 20.5 401Example 6 hexagonal pyramid- 70 2.8 20.1 390 shaped, small pyramid- shaped and granularExample 7 hexagonal pyramid-shaped 40 3.3 20.8 305 and granularExample 8 hexagonal pyramid-shaped 100 2.5 19.1 399Example 9 hexagonal pyramid- 70 2.7 19.3 390 shaped, small pyramid- shaped and granularExample 10 hexagonal pyramid-shaped 40 3.3 18.8 305 and granularExample 11 hexagonal pyramid-shaped 100 2.5 0 395Example 12 hexagonal pyramid- 70 2.7 0 379 shaped, small pyramid- shaped and granularExample 13 hexagonal pyramid-shaped 40 3.3 0 288 and granularExample 14 hexagonal pyramid-shaped 35 1.8 0 216 and granularExample 15 granular 0 .ltoreq.0.1 0 175__________________________________________________________________________
The grain size of the hexagonal pyramid-shaped Fe crystals is an average value of distances between opposed corners on the opposite sides of an apex, i.e., of lengths of three diagonal lines. In calculating the pseudo-area rate B of the heteromorphic hexagonal pyramid-shaped Fe crystals, a notch was provided in a disk, and then, the disk was cooled for 5 minutes or more in liquid nitrogen. Thereafter, the disk and the slide surface construction were broken at the notch, and a photomicrograph of the vertical section of the slide surface construction was taken. In this way, the pseudo-area rate B of the heteromorphic hexagonal pyramid-shaped Fe crystals was determined based on such photomicrograph in the above-described manner.
FIG. 33 A is a photomicrograph showing the crystal structure of the slide surface in the example 1, and FIG. 33B is a photomicrograph showing the crystal structure of a vertical section in the example 1. FIG. 33C is an enlarged photomicrograph showing an essential portion shown in FIG. 33B. In FIG. 33A, a large number of hexagonal pyramid-shaped Fe crystals are observed. In this case, the area rate A of the hexagonal pyramid-shaped Fe crystals is equal to 100%, as shown in Table 17. Each of the hexagonal pyramid-shaped Fe crystal is a {222} oriented Fe crystal with its (hhh) plane, i.e., {222} plane oriented toward the slide surface. The content S of the {222} oriented Fe crystals is equal to 96.2%, as shown in Table 16 and FIG. 30. The hexagonal pyramid-shaped Fe crystal are heteromorphic hexagonal pyramid-shaped Fe crystals each having notched recess(es), as apparent from FIGS. 33B and 33C. The pseudo-area rate B of the heteromorphic hexagonal pyramid-shaped Fe crystals is equal to 100%, as shown in Table 17.
FIG. 34 is a photomicrograph showing the crystal structure of the slide surface in the example 11, wherein a large number of hexagonal pyramid-shaped Fe crystals are observed. In this case, the area rate A of the hexagonal pyramid-shaped Fe crystals is equal to 100%, as shown in Table 17. Each of the hexagonal pyramid-shaped Fe crystals is likewise a {222} oriented Fe crystal. The content S of the {222} oriented Fe crystals is equal to 96.5%, as shown in Table 16 and FIG. 31. However, the hexagonal pyramid-shaped Fe crystal are normal hexagonal pyramid-shaped Fe crystals and hence, the pseudo-area rate B of the heteromorphic hexagonal pyramid-shaped Fe crystals is equal to 0%, as shown in Table 17.
FIG. 35 is a photomicrograph showing the crystal structure of the slide surface in the example 15, wherein a large number of granular Fe crystals are observed. In this case, the area rate of the hexagonal pyramid-shaped Fe crystals is equal to 0%, as shown in Table 17.
Then, disks having the slide surface construction of the examples 1 to 15 were subjected to a seizure test in a chip-on-disk manner under lubrication to measure the seizure generating load, thereby providing the results given in Table 18. The conditions for the seizure test were as follows: the material for the chip was chromemolybdenum steel (JIS SCM429, a carburized material); the peripheral speed of the disk was 15 m/sec; the lubricating method was to apply a molybdenum disulfide onto a surface of each example of the disk; the area of the slide surface of the chip was 1 cm.sup.2 ; and the method for applying load to the chip was to apply first a load of 20 N and maintain it for 2 minutes and after that, the load was increased in sequence by 20 N while maintaining it for 2 minutes each time the load was increased.
TABLE 18______________________________________Slide surface construction Seizure generating load (N)______________________________________Example 1 740Example 2 710Example 3 630Example 4 650Example 5 550Example 6 540Example 7 520Example 8 410Example 9 410Example 10 380Example 11 400Example 12 400Example 13 370Example 14 230Example 15 220______________________________________
FIG. 36 shows the relationship between the area rate A of the hexagonal pyramid-shaped Fe crystals and the seizure generating load.
If the examples 1 to 13 are compared with the examples 14 and 15 in FIG. 36, the former examples are substantially higher in seizure generating load, as compared with the latter examples. From this, it can be seen that the area rate of the hexagonal pyramid-shaped Fe crystals in the slide surface advantageously may be set in a range of A.gtoreq.40%.
If the examples 1 to 7 are compared with the examples 8 to 13 when the area rate A is equal to or higher than 40%, the former examples have a seizure resistance superior to the latter examples. From this, it can be seen that the pseudo-area rate B of the heteromorphic hexagonal pyramid-shaped Fe crystals advantageously may be set in a range of B.gtoreq.20%.
Then, using disks having the construction of examples 1 to 3 and 11 to 15, the dynamic friction coefficient .mu. was measured in a chip-on-disk manner under lubrication, thereby providing the results given in Table 19. The conditions for this test are were follows: the material for the chip was chromemolybdenum steel (JIS SCM420, a carburized material); the peripheral speed of the disk was 15 m/sec; a lubricating oil corresponding to 10W-30 at room temperature (in SAE viscosity classification) was used; the amount of oil supplied was 40 ml/min; the area of the slide surface of the chip was 1 cm.sup.2 ; the method for applying load to the chip was to first apply a load of 50 N and maintain it for 2 minutes and after that, the load was increased in sequence by 50 N while maintaining it each time the load was increased. When the load reached 250 N, the chip was maintained for 5 minutes and the dynamic friction coefficient .mu. was measured.
TABLE 19______________________________________Slide surface construction Dynamic friction coefficient .mu.______________________________________Example 1 0.014Example 2 0.014Example 3 0.016Example 11 0.013Example 12 0.014Example 13 0.015Example 14 0.04Example 15 0.042______________________________________
FIG. 37 shows the relationship between the area rate A of the hexagonal pyramid-shaped Fe crystals and the dynamic friction coefficient .mu..
As is apparent from FIG. 37, when the area rate A of the hexagonal pyramid-shaped Fe crystals in the slide surface is equal to or higher than 40%, the dynamic friction coefficients .mu. of the examples 1 to 3 including the heteromorphic hexagonal pyramid-shaped Fe crystals existing in the slide surface are substantially equal to those of the examples 11 to 13 including no heteromorphic hexagonal pyramid-shaped Fe crystals existing in the slide surface. From this, it can be seen that the existence of the heteromorphic hexagonal pyramid-shaped Fe crystals in the slide surface does not exert any influence on the wear resistance of the slide surface construction.
Example-2
A slide surface construction 9 formed of an aggregate of Fe crystals and having a thickness of 15 .mu.m was formed on a meshed face 27 of a gear 26 made of a chromemolybdenum steel (JIS SCM420, a carburized material) by an electrolytic Fe plating process comprising first and second steps.
Table 20 shows the conditions for the plating bath for examples 1 to 12 of the slide surface construction, and Tables 21 and 22 show energizing conditions for the examples 1 to 12.
TABLE 20______________________________________Plating bathFerrous sulfate (g/liter) pH Temperature (.degree.C.)______________________________________400 6 50______________________________________
TABLE 21__________________________________________________________________________Slide First step Energizationsurface T.sub.3 T.sub.1 CDmax Plating stopping stepconstruction (msec) (msec) T.sub.3 /T.sub.4 CD.sub.1 (A/dm.sup.2) (A/dm.sup.2) time (min) T.sub.2 (msec)__________________________________________________________________________Example 1 2 8 0.2 4 20 12 800 (100T.sub.1)Example 2Example 3Example 4Example 5Example 6 8000 (1000T.sub.1)__________________________________________________________________________Second stepSlide Platingsurface T.sub.3 T.sub.1 CDmax timeconstruction (msec) (msec) T.sub.3 /T.sub.4 CD.sub.2 (A/dm.sup.2) (A/dm.sup.2) (min)__________________________________________________________________________Example 1 2 8 0.2 6 (1.5 CD.sub.1) 30 2Example 2 5.6 28 2.1 (1.4 CD.sub.1)Example 3 4.8 24 2.5 (1.2 CD.sub.1)Example 4 4.4 22 2.7 (1.1 CD.sub.1)Example 5 4 (1.0 CD.sub.1) 20 3Example 6 5.2 26 2.3 (1.3 CD.sub.1)__________________________________________________________________________
TABLE 22__________________________________________________________________________Slide First step Energizationsurface T.sub.3 T.sub.1 CDmax Plating stopping stepconstruction (msec) (msec) T.sub.3 /T.sub.4 CD.sub.1 (A/dm.sup.2) (A/dm.sup.2) time (min) T.sub.2 (msec)__________________________________________________________________________Example 7 2 8 0.2 4 20 12 720 (90T.sub.1)Example 8Example 9Example 10Example 11Example 12 792 (99T.sub.1)__________________________________________________________________________Slide Second stepsurface T.sub.3 T.sub.1 CDmax Platingconstruction (msec) (msec) T.sub.3 /T.sub.4 CD.sub.1 (A/dm.sup.2) (A/dm.sup.2) time (min)__________________________________________________________________________Example 7 2 8 0.2 6 (1.5 CD.sub.1) 30 2Example 8 5.6 28 2.1 (1.4 CD.sub.1)Example 9 4.8 24 2.5 (1.2 CD.sub.1)Example 10 4.4 22 2.7 (1.1 CD.sub.1)Example 11 4 (1.0 CD.sub.1) 20 3Example 12 5.2 26 2.3 (1.3 CD.sub.1)__________________________________________________________________________
Table 23 shows the content S of the oriented Fe crystals for the examples 1 to 12. The content S was determined in the same manner as in the first embodiment.
TABLE 23______________________________________Slide surface Content S (%) of oriented Fe crystalsconstruction {110} {200} {211} {310} {222}______________________________________Example 1 0 0 1.9 0 98.1Example 2 0 0 3.1 0 96.9Example 3 0 0 2.7 0 97.3Example 4 0.3 0 4.5 0 95.2Example 5 0.2 0 3.7 0 96.1Example 6 0 0 3.2 0 96.8Example 7 0 0 4.1 0 95.9Example 8 0.4 0 3 0 96.6Example 9 0 0 2.8 0 97.2Example 10 0 0 4.2 0 95.8Example 11 0.1 0 3.2 0 96.7Example 12 0 0 3.9 0 96.1______________________________________
Table 24 shows the crystal form of the slide surface, the area rate A and grain size of the hexagonal pyramid-shaped Fe crystals in the slide surface, the pseudo-area rate B of the heteromorphic hexagonal pyramid-shaped Fe crystals, and the hardness of a vertical section of the slide surface construction for the examples 1 to 12. The area rate A, the grain size and the pseudo-area rate B were determined in the same manner as that described above.
TABLE 24__________________________________________________________________________ Hexagonal pyramid- Pseudo-area rate B (%) ofSlide Crystal form shaped Fe crystals heteromorphic hexagonalsurface of slide Area rate Grain pyramid-shaped Fe Hardnessconstruction surface A (%) size (.mu.m) crystals HmV__________________________________________________________________________Example 1 Hexagonal 100 2.5 100 408Example 2 pyramid-shaped 89.4Example 3 20.5Example 4 19.1Example 5 0Example 6 40.8Example 7 12.3Example 8 12.4Example 9 11.8Example 10 12.1Example 11 0Example 12 16.1__________________________________________________________________________
FIG. 38 shows the relationship between the average cathode current density CD.sub.2 in the second step and the pseudo-area rate B (%) of the heteromorphic hexagonal pyramid-shaped Fe crystals by the time T.sub.2 required for the energization stopping step.
As apparent from Table 24 and FIG. 38, the pseudo-area rate B of the heteromorphic hexagonal pyramid-shaped Fe crystals in the slide surface for the examples 1 to 3 and 6 is equal to or higher than 20%. From this, it may be safely mentioned that in order to set the pseudo-area rate B in a range of B.gtoreq.20%, it is necessary to establish a relation, T.sub.2 .gtoreq.100 T.sub.1 between the time T.sub.2 required for the energization stopping step and the minimum current maintaining time T.sub.1, and to establish a relation, CD.sub.2 .gtoreq.1.2 CD.sub.1 between the average cathode current density CD.sub.2 in the second step and the average cathode current density CD.sub.2 in the first step.
The second embodiment is not limited to the gear, and is applicable to a quick joint, an upper arm, a lower arm and the like to which a solid or semi-solid lubricating agent is applied. In this case, the responsiveness is enhanced by a reduction in friction.
THIRD EMBODIMENT
Referring to FIG. 39, a cylinder block 34 for an internal combustion engine includes a cylinder block body 35 made of an aluminum alloy, and a cylinder sleeve 36 made of a cast iron. A lamellar slide surface construction 9 is formed on an inner peripheral surface 37 of the cylinder sleeve 36 by a plating treatment. A piston 19 made of an aluminum alloy is slidably received in the cylinder sleeve 36.
The slide surface construction 9 is formed of an aggregate of metal crystals having a body-centered cubic structure (which will be also referred to as a bcc structure hereinafter), as shown in FIG. 5. The aggregate includes a large number of (hhh) oriented metal crystals 14 which are grown into a columnar shape from the inner peripheral surface 37 of the cylinder sleeve 36 with their (hhh) planes (by Miller indices) oriented toward a slide surface 12, or a large number of (2hhh) oriented metal crystals 14 which are grown into a columnar shape from the inner peripheral surface 37 of the cylinder sleeve 36 with their (2hhh) planes (by Miller indices) oriented toward the slide surface 12, as shown in FIG. 40.
When the aggregate of the metal crystals having the bcc structure includes the large number of (hhh) oriented metal crystals 14 grown into a columnar shape from the inner peripheral surface 37 of the cylinder sleeve 36 with their (hhh) planes (by Miller indices) oriented toward the slide surface 12, as described above, the tip ends of the (hhh) oriented metal crystals 14 can be formed into rounded hexagonal pyramid-shaped metal crystals (rounded pyramid-shaped metal crystals) 38 in the slide surface, as shown in FIGS. 41, 42A and 42B. The rounded hexagonal pyramid-shaped metal crystals 38 are small in average grain size and substantially uniform in grain size, as compared with rounded trigonal pyramid-shaped metal crystals which are likewise (hhh) oriented metal crystals. In the rounded hexagonal pyramid-shaped metal crystals 38, there is an interrelation between the grain size and the height. Therefore, the grain size being substantially uniform, indicates that the heights are substantially equal to one another.
Each of ridgelines 39 in the rounded hexagonal pyramid-shaped metal crystal 38 assumes a convex arcuate shape, and each slope-correspondence area 40 between the adjacent ridgelines 39 comprises two band-like regions each of which is one of two slopes forming each ridgeline 39, and a V groove-like region 44 which is connected to both the band-like region and whose opening width is gradually reduced from a skirt portion 42 toward an apex 43.
The area rate A of the rounded hexagonal pyramid-shaped metal crystals 38 in the slide surface 12 is set in a range of 40%.ltoreq.A.ltoreq.100%.
If the area rate A is set in such range, adjacent ones of the rounded hexagonal pyramid-shaped metal crystals 38 assume mutually biting states, as shown in FIG. 41. Thus, the slide surface takes on a very intricate aspect comprising a large number of extremely fine crests 31, a large number of extremely fine valleys 32 formed between the crests 31, and a large number of extremely fine swamps 33 formed due to the mutual biting of the crests 31.
In this case, if each of the ridgelines 39 of the hexagonal pyramid-shaped metal crystal 16 is rectilinear and the apex 43 of the hexagonal pyramid-shaped metal crystal 16 is pointed, as shown in FIG. 43, and if the slope-correspondence area 40 between the adjacent ridgelines 39 is formed into a relatively deep V groove-like shape such that the opening width is gradually reduced from the skirt portion 42 toward the apex 43, namely, if the hexagonal pyramid-shaped metal crystals 16 are angular, the flow of oil lacks a smoothness, when the viscosity of the oil is high at a lower temperature or the like, because the angular pyramid-shaped metal crystals 16 performs an occluding effect.
In contrast, if the rounded pyramid-shaped metal crystals 38 as described above are formed to exist in the slide surface 12, the flow resistance of the oil with a high viscosity is reduced in the slide surface 12 and therefore, the oil can be allowed to flow smoothly. Thus, the shear resistance of an oil film formed on the slide surface 12 can be reduced to reduce the friction loss.
From the fact that the slide surface 12 takes on the very intricate aspect, as described above, the slide surface construction 9 has a good oil retention, substantially irrespective of the viscosity of the oil. Thus, the slide surface construction 9 exhibits an excellent seizure resistance, even if it is placed in a severe sliding environment. On the other hand, even under non-lubrication, the dispersion of a sliding load is provided by the large number of fine rounded hexagonal pyramid-shaped metal crystals 38 and therefore, the seizure resistance of the slide surface construction 9 is relatively good.
Further, as a result, uniform fine division of the rounded hexagonal pyramid-shaped metal crystals 38, a local increase in surface pressure can be avoided and a fine division of the sliding load can be achieved. Thus, the slide surface construction 9 exhibits an excellent wear resistance not only under lubrication but also under non-lubrication.
In the rounded hexagonal pyramid-shaped metal crystals 38, it is possible to form a valley portion 45 of the V groove-like region 44, so that the valley portion 45 assumes a convex arcuate shape to follow the ridgeline 39. If the valley portion 45 is formed in this manner, the V groove-like region 44 becomes narrow and hence, the flowability of a high-viscosity oil can be further enhanced.
When the aggregate of the metal crystals having the bcc structure includes the large number of (2hhh) oriented metal crystals with their (2hhh) plane (by Miller indices) oriented toward the slide surface 12, the tip ends of the (2hhh) oriented metal crystals can be formed into rounded small pyramid-shaped metal crystals. Even when the rounded pyramid-shaped metal crystals such as the rounded hexagonal and trigonal pyramid-shaped and small pyramid-shaped metal crystals exists in combination in the slide surface 12, the area rate A of these rounded pyramid-shaped metal crystals in the slide surface 12 is set in a range of 40%.ltoreq.A.ltoreq.100%.
As shown in FIG. 8, the inclination of the (hhh) plane with respect to the phantom plane 18 along the slide surface 12 appears as the inclination of the rounded hexagonal pyramid-shaped metal crystals 38 and the like and hence, an influence is imparted to the oil retention and the wear resistance of the slide surface construction. The inclination angle .theta. formed by the (hhh) plane with respect to the phantom plane 18 is set in a range of 0.degree..ltoreq..theta..ltoreq.15.degree. as in the first embodiment. In this case, the direction of inclination of the (hhh) plane is not limited. If the inclination angle .theta. is larger than 15.degree., the oil retention and the wear resistance of the first region R.sub.1 are reduced. The inclination angle .theta. also applies to the (2hhh) plane.
Examples of the metal crystals having the bcc structure are those of simple metals such as Fe, Cr, Mo, W, Ta, Zr, Nb, V and the like, or those of alloys thereof, as in the first embodiment.
In the plating treatment for forming the slide surface construction 9, the conditions for the plating bath in carrying out an electrolytic Fe plating are as shown in Table 25.
TABLE 25______________________________________Plating bathFerrous sulfate(g/liter) pH Temperature (.degree.C.)______________________________________100-400 3-7 40-70______________________________________
The adjustment of pH is carried out using ammonia water.
A pulse current process is mainly utilized as an energizing method, as shown in FIG. 9, as in the first embodiment. In the pulse current process, if an energization time from the start of increasing to the start of dropping of an electric current I is represented by T.sub.ON, and a cycle time is represented by T.sub.C, wherein one cycle is defined as being from the start of proceeding increasing to the start of succeeding increasing, the ratio of the energization time T.sub.ON to the cycle time T.sub.C, i.e., the time ratio Y.sub.ON /T.sub.C is set in a range of T.sub.ON /T.sub.C .ltoreq.0.45. The maximum cathode current density CDmax is set in a range of CDmax.gtoreq.0.22 A/dm.sup.2, and the average cathode density CDm is set in a range of 0.1 A/dm.sup.2 .ltoreq.CDm.ltoreq.10 A/dm.sup.2.
If such a pulse current process is utilized, the ion concentration in the vicinity of a cathode is uniformized due to the fact that the maximum electric current alternately flows and does not flow in the plating bath. Thus, the composition of the slide surface construction can be stabilized.
In the above-described electrolytic Fe plating process, the precipitation and content of the (hhh) oriented Fe crystals or the (2hhh) oriented Fe crystals and the like are controlled by changing the plating bath conditions and the energizing conditions. This control is easy under the utilization of the pulse current process and hence, the slide surface 12 is easily formed into an intended form.
In addition to the electrolytic Fe plating, other examples of a plating process are a PVD process, a CVD process, a sputtering process, an ion plating and the like, which are gas-phase plating processes. The conditions for carrying out a W or Mo plating by the sputtering process were as follows: For example, the Ar gas pressure was 0.2 to 1 Pa; the average Ar gas accelerating electric power was D.C. 1 to 2.5 kW; and the substrate temperature was 150 to 450.degree. C. The conditions for carrying out a W plating by the CVD process were as follows: For example, the starting material was WF6; the flow rate of a gas was 2 to 15 cc/min; the pressure in a chamber was 50 to 300 Pa; the substrate temperature was 400 to 650.degree. C.; and the average output of ArF excimer laser was 5 to 60 W.
A specified example will be described below.
For simulating of a cylinder sleeve 36, as shown in FIG. 44, a slide surface construction 9 formed of an aggregate of Fe crystals and having a thickness of 15 .mu.m was formed by subjecting an outer peripheral surface of a round bar 46 made of cast iron (JIS FC250) and having a diameter of 6.5 mm to an electrolytic Fe plating process.
Table 26 shows the conditions for the electrolytic Fe plating process for examples 1 to 8 of the slide surface construction. The plating time was varied within 5 to 60 minutes in order to set the thickness of the examples 1 to 8 at 15 .mu.m, as described above.
TABLE 26__________________________________________________________________________Plating bathSlide Ferrous Pulse current processsurface sulfate Temperature CDmaxconstruction (g/liter) pH (.degree. C.) (A/dm.sup.2) CDm (A/dm.sup.2) T.sub.ON /T.sub.C T.sub.ON (msec)__________________________________________________________________________Example 1 400 6.5 65 40 8 0.2 2Example 2 350 6.3 60 27.5 5.5 0.2 2Example 3 300 6 60 20 4 0.2 2Example 4 400 6 50 20 4 0.2 2Example 5 300 6 50 15 3 0.2 2Example 6 250 5.5 50 15 3 0.2 2Example 7 200 4.5 50 17.5 3.5 0.2 2Example 8 200 3 50 2.5 0.5 0.2 2__________________________________________________________________________
Table 27 shows the crystal form of the slide surface, the content A and grain size of the rounded and/or angular hexagonal pyramid-shaped Fe crystals in the slide surface, the content S of the oriented Fe crystals, and the hardness of a section of the slide surface construction for the examples 1 to 8.
TABLE 27__________________________________________________________________________ Rounded and angular hexagonal pyramid-Slide Crystal form shaped Fe crystals Content S (%) of oriented Fesurface of slide Area rate Grain crystalsconstruction surface A (%) size (.mu.m) {110} {200} {211} {310} {222} Hardness HmV__________________________________________________________________________Example 1 Rounded 100 2 0 0 1.9 0 98.1 435 hexagonal pyramid-shapedExample 2 Rounded 70 2.3 5.4 2.9 16.1 2.1 73.5 401 hexagonal pyramid-shaped and granularExample 3 Rounded 40 1.7 21.9 3.6 31.1 2.6 40.8 356 hexagonal pyramid-shaped and granularExample 4 Angular 100 1.8 0 0 3.5 0 96.5 410 hexagonal pyramid-shapedExample 5 Angular 70 1.8 6 3.9 17.6 2.6 69.9 392 hexagonal pyramid-shaped and granularExample 6 Angular 40 2 21.8 3.5 30.8 2.4 41.5 352 hexagonal pyramid-shaped and granularExample 7 Angular 35 1.7 19.4 12.4 19.7 13 35.5 246 hexagonal pyramid-shaped and granularExample 8 Granular 0 -- 33.6 16.5 17.5 17.7 14.7 210__________________________________________________________________________
The area rate A of the rounded and angular hexagonal pyramid-shaped Fe crystals was determined according to an equation, A=(c/b.times.100(%), wherein b represents an area of the slide surface, and c represents an area occupied by all the rounded and angular hexagonal pyramid-shaped Fe crystals in the slide surface. The grain size of the rounded and angular hexagonal pyramid-shaped Fe crystals is an average value of distances between opposed corners on the opposite sides of an apex, i.e., of lengths of three diagonal lines.
The content S of the oriented Fe crystals was determined in the same manner as in the first embodiment, based on the X-ray diffraction patterns (X-ray was applied in a direction perpendicular to the slide surface) for the examples 1 to 8. FIG. 45 is the X-ray diffraction pattern for the example 1, FIG. 46 is the X-ray diffraction pattern for the example 4, and FIG. 47 is the X-ray diffraction pattern for the example 8.
FIG. 48A is a photomicrograph of the example 1, FIG. 48B is an enlarged photomicrograph taken from FIG. 48A, and FIG. 48C is an enlarged photomicrograph taken from FIG. 48B. In these photomicrographs, a large number of rounded hexagonal pyramid-shaped Fe crystals are observed. In this case, the area rate A of the rounded hexagonal pyramid-shaped Fe crystals is equal to 100%, as shown in Table 27. Each of the rounded hexagonal pyramid-shaped Fe crystals is a {222} oriented Fe crystal with its (hhh) plane, i.e., {222} plane oriented toward the slide surface. The content S of the {222} oriented Fe crystals is equal to 98.1%, as shown in Table 27 and FIG. 45. The area rate A was calculated for the rounded hexagonal pyramid-shaped Fe crystals, including pyramid-shaped Fe crystals which were incompletely grown to have five ridgelines, as shown in FIG. 48B, but supposed to be completely grown to have six ridgelines.
FIG. 49 is a photomicrograph showing the crystal form of the slide surface in the example 3, wherein a plurality of rounded hexagonal pyramid-shaped Fe crystals are observed. In this case, the area rate A of the rounded hexagonal pyramid-shaped Fe crystals is equal to 40%, as shown in Table 27. This area rate A was calculated in the same manner as in the example 1.
FIG. 50 is a photomicrograph showing the crystal form of the slide surface in the example 4, wherein a large number of angular hexagonal pyramid-shaped Fe crystals are observed. In this case, the area rate A of the angular hexagonal pyramid-shaped Fe crystals is equal to 100%, as shown in Table 27. Each of the angular hexagonal pyramid-shaped Fe crystals is a {222} oriented Fe crystal with its (hhh) plane, i.e., {222} plane oriented toward the slide surface. The content S of the {222} oriented Fe crystals is equal to 96.5%, as shown in FIG. 44.
If the example 1 is compared with the example 4; the example 2 is compared with the example 5, and the example 3 is compared with the example 6 in Tables 26 and 27, the pH and temperature as well as even the concentration of ferrous sulfate of the plating bath for the examples 1, 2 and 3 tend to be high, as compared with those for the examples 4, 5 and 6. It is believed that the rounded hexagonal pyramid-shaped Fe crystals are precipitated in the examples 1, 2 and 3 due to the above fact.
If the example 1 shown in FIG. 48C is compared with the example 3 shown in FIG. 49, the valley bottom in the V groove-like region in the example 1 is arcuate, but the valley bottom in the V groove-like region in the example 3 is near rectilinear. As a result, the depth of the V groove-like region in the example 1 is shallower than that in the example 3. This is attributable to the fact that the example 1 is high in maximum cathode current density CDmax and average cathode current density CDm and also high in pH, as compared with the example 3.
FIG. 51 is photomicrograph showing the crystal form of the slide surface in the example 8, wherein a large number of granular Fe crystals are observed.
Then, the dynamic friction coefficient .mu. for the examples 1 to 8 was measured using a Fabry friction tester by a method which will be described below.
First, in order to reproduce an oil having a high viscosity at a lower temperature, an oil corresponding to 10W-30 (in SAE viscosity classification) and PAMA (polyalkyl methacrylate) were mixed in a proportion of 71:29 (calculated according to JIS K2283) by volume percentage (%) to prepare an oil mixture having a dynamic viscosity of 364 cSt. The dynamic viscosity of the oil corresponding to 10W-30 at ambient temperature was 90 cSt, and that of the PAMA was 128500 cSt.
As shown in FIG. 52, a portion of the round bar 46 having a slide surface construction 9 formed thereon was clamped by a pair of V-blocks 50 made of a steel (JIS SCM420, a carburized material) and immersed in the oil mixture. The round bar 46 was rotated at 300 rpm in the oil mixture, and a test load of 3.6 N was applied to the round bar 46 by both the V blocks 47. After a lapse of 2 minutes from the time when the load on the round bar 46 reached the test load, the dynamic friction coefficient .mu. was measured. Results are given in Table 28.
TABLE 28______________________________________Slide surface construction Dynamic friction coefficient .mu.______________________________________Example 1 0.166Example 2 0.186Example 3 0.267Example 4 0.236Example 5 0.243Example 6 0.315Example 7 0.469Example 8 0.472______________________________________
FIG. 53 shows the relationship between the area rate A of the rounded and angular hexagonal pyramid-shaped Fe crystals and the dynamic friction coefficient .mu.. As is apparent from FIG. 53, if the area rate A of the rounded and angular hexagonal pyramid-shaped Fe crystals is set in a range of A.gtoreq.40% as in the examples 1 to 3 and 4 to 6, it can be seen that the dynamic friction coefficient .mu. is remarkably reduced. This is because the solid contact is avoided by an oil retention enhancing effect provided by the rounded and angular hexagonal pyramid-shaped Fe crystals.
If the examples 1 to 3 and the examples 4 to 6 having the same area rate A of the rounded and angular hexagonal pyramid-shaped Fe crystals in the range of A.gtoreq.40% are compared with each other (the example 1 with the example 4; the example 2 with the example 5; and the example 3 with the example 6), it can be also seen that the dynamic friction coefficient .mu. of the examples 1 to 3 having the rounded hexagonal pyramid-shaped Fe crystals in the slide surface is lower than those of the examples 4 to 6 having the angular hexagonal pyramid-shaped Fe crystals by about 15 to about 30%. This is attributable to the fact the flow of the oil mixture of the high viscosity in the examples 1 to 3 is smooth, as compared with that in the examples 4 to 6.
Therefore, by providing the examples 1 to 3, particularly the examples 1 and 2 on the inner peripheral surface of the cylinder sleeve, the friction loss can be reduced, even when the viscosity of the oil is high at a low temperature and the like.
Then, examples 1 to 8 of slide surface constructions were formed on an outer periphery of one surface of a disk made of a cast iron (JIS FC250) in the same manner as that described above and subjected to a seizure test in a chip-on-disk manner under lubrication to measure the seizure generating load, thereby providing the results given in Table 29. Conditions for the seizure test were as follows: the material for the chip was an aluminum alloy (JIS AC8A, T7-treated material); the peripheral speed of the disk was 15 m/sec; an oil corresponding to 10W-30 at room temperature was used; the amount of oil supplied was 40 ml/min; the area of the slide surface of the chip was 1 cm.sup.2 ; the method for applying load to the chip was to first apply a load of 20 N and maintain it for 2 minutes and after that, the load was increased in sequence by 20 N while maintaining it each time the load was increased.
TABLE 29______________________________________Slide surface construction Seizure generating load (N)______________________________________Example 1 1480Example 2 1170Example 3 820Example 4 1450Example 5 1150Example 6 850Example 7 330Example 8 280______________________________________
FIG. 54 is a graph taken from Table 29. As is apparent from FIG. 54, the seizure generating loads for the examples 1 to 3 are substantially equal to those in the examples 4 to 6, respectively, when the area rate A is in the range of A.gtoreq.40%. From this, it was made clear that even if the rounded hexagonal pyramid-shaped Fe crystals exist in the slide surface, a seizure resistance equivalent to that provided when the angular hexagonal pyramid-shaped Fe crystals exist in the slide surface, can be obtained.
The third embodiment is not limited to the cylinder sleeve and is applicable to various slide members such as a piston, a cam shaft, a piston ring, a cylinder sleeve and the like.
FOURTH EMBODIMENT
Referring to FIG. 55, a piston 19 for an internal combustion engine includes a piston body 19a made of an aluminum alloy. A lamellar slide surface construction 9 is formed on outer peripheral surfaces of a land portion 20 and a skirt portion 21 of the piston body 19a by plating.
The slide surface construction 9 is formed of an aggregate of metal crystals having a body-centered cubic structure (which will be also referred to as a bcc structure hereinafter), as shown in FIG. 5. The aggregate includes a plurality of columnar crystals 28 grown from the piston body 19a, as shown in FIG. 56. Each of the columnar crystals 28 is a (hhh) oriented metal crystal with its (hhh) plane (by Miller indices) oriented toward a slide surface. As also shown in FIG. 57, each of the tip ends of the columnar crystals is in the form of a truncated hexagonal pyramid-shaped metal crystal (truncated pyramid-shaped projection) 48 in the slide surface 12. The area rate A of the truncated hexagonal pyramid-shaped metal crystals 48 in the slide surface is set in a range of 40%.ltoreq.A.ltoreq.100%.
As clearly shown in FIG. 58A, a top face of the truncated hexagonal pyramid-shaped metal crystal 48 is formed of a plurality of flat face portions 49a, 49b, 49c, 49d, 49e and 49f. Steps "s" are provided between adjacent flat face portions 49a and 49b; 49b and 49c; 49c and 49d; 49d and 49e; 49e and 49f; and 49f and 49a, respectively, as shown in FIG. 58B.
In the illustrated embodiment, the top face 49 is divided into the six flat face portions 49a to 49f by three dividing lines L.sub.3, L.sub.4 and L.sub.5 which interconnect three sets of two opposed sides to bisect the opposed sides and which extend through an inner center o. The flat face portions 49a to 49f comprise three protruding flat face portions 49a, 49c and 49e and three depressed flat face portions 49b, 49d and 49f, which are alternately located about the inner center o. In this case, the step "s" is of about 0.1 to about 0.5 .mu.m.
If the area rate A of the truncated hexagonal pyramid-shaped metal crystals 48 in the slide surface 12 is set in the above-described range, the adjacent ones of the truncated hexagonal pyramid-shaped metal crystals 48 assume mutually biting states, as shown in FIG. 57. Thus, the slide surface takes on a very intricate aspect comprising a large number of extremely fine crests 31, a large number of complicated and extremely fine valleys 32 formed between the crests 31 and extending at random, and a large number of extremely fine swamps 33 formed due to the mutual biting of the crests 31. Moreover, the intricateness is doubled by the fact that the top face 49 of the truncated hexagonal pyramid-shaped metal crystal 48 is formed of the six flat face portions 49a to 49f and the steps "s" are provided between the adjacent flat face portions 49a and 49b to 49f and 49a. As a result, the flow resistance of the oil on the slide surface 12 is remarkably increased.
Thus, it is possible to remarkably enhance the oil retention of the slide surface construction and hence, even in a severe sliding environment, the solid contact can be reduced to the utmost, causing the slide surface construction 9 to exhibit an excellent seizure resistance. In addition, because the top face 49 has the flat face portions 49a to 49f, the friction coefficient .mu. can be reduced, causing the slide surface construction to exhibit an excellent wear resistance in the severe sliding environment.
As shown in FIG. 8, the inclination of the (hhh) plane with respect to the phantom plane 18 along the slide surface 12 appears as the inclination of the truncated hexagonal pyramid-shaped metal crystals 48 and hence, an influence is imparted to the oil retention of the slide surface construction. The inclination angle .theta. formed by the (hhh) plane with respect to the phantom plane 18 is set in a range of 0.degree..ltoreq..theta..ltoreq.15.degree. as in the first embodiment. In this case, the direction of inclination of the (hhh) plane is not limited. If the inclination angle .theta. is larger than 15.degree., the oil retention and the wear resistance of the slide surface construction 9 are reduced.
Examples of the metal crystals having the bcc structure are those of simple metals such as Fe, Cr, Mo, W, Ta, Zr, Nb, V and the like, or those of alloys thereof, as in the first embodiment.
In producing the slide surface construction 9, the following steps are employed: a step for forming a deposit layer 50 including a plurality of hexagonal pyramid-shaped metal crystals 16 in a surface which becomes a slide surface 12 with an area rate A of the hexagonal pyramid-shaped metal crystals 16 in the surface being in a range of 40%.ltoreq.A.ltoreq.100%, on outer peripheral surfaces of the land portion 20 and the skirt portion 21 of the piston body 19a by plating, as shown in FIGS. 59 and 60; a step for subjecting the surface of the deposit layer 50 to a polishing to form the hexagonal pyramid-shaped metal crystals 16 into truncated hexagonal pyramid-shaped metal crystals 48 each having a top face, as shown in FIG. 61; and a step for subjecting the polished surface of the deposit layer 50 to an etching treatment to divide the top face of the truncated hexagonal pyramid-shaped metal crystal 48 into six flat face portions 49a to 49f and to provide steps "s" between the adjacent flat face portions 49a and 49b to 49f and 49a, as shown in FIGS. 56 to 58B.
In the plating treatment for forming the deposit layer 50, conditions for a plating bath in carrying out an electrolytic Fe plating process are as given in Table 30.
TABLE 30______________________________________Plating bathFerrous sulfate(g/liter) pH Temperature (.degree.C.)______________________________________100-400 3-6.8 10-60______________________________________
A pulse current process is mainly utilized as an energizing method, as shown in FIG. 9, as in the first embodiment. In the pulse current process, the ratio of the energization time T.sub.ON to the cycle time T.sub.C, i.e., the time ratio T.sub.ON /T.sub.C is set in a range of T.sub.ON /T.sub.C .ltoreq.0.45. The maximum cathode current density CDmax is set in a range of CDmax.gtoreq.2 A/dm.sup.2, and the average cathode current density CDm is set in a range of 1 A/dm.sup.2 .ltoreq.CDm.ltoreq.10 A/dm.sup.2.
If such a pulse current process is utilized, the ion concentration in the vicinity of a cathode is uniformized due to the fact that the maximum electric current alternately flows and does not flow in the plating bath. Thus, the composition of the slide surface construction can be stabilized.
In the above-described electrolytic Fe plating process, the precipitation and content of the (hhh) oriented Fe crystals, i.e., Fe crystals with their tip ends being in the form of hexagonal pyramid-shaped Fe crystals 16 and the like are controlled by changing the plating bath conditions and the energizing conditions.
In addition to the electrolytic Fe plating, other examples of a plating process are a PVD process, a CVD process, a sputtering process, an ion plating and the like, which are gas-phase plating processes. Conditions for carrying out a W or Mo plating by the sputtering process were as follows: For example, the Ar gas pressure was 0.2 to 1 Pa; the average Ar gas accelerating electric power was D.C. 1 to 1.5 kW; and the substrate temperature was 150 to 300.degree. C. Conditions for carrying out a W plating by the CVD process were as follows: For example, the starting material was WF.sub.6 ; the flow rate of a gas was 2 to 15 cc/min; the pressure in a chamber was 50 to 300 Pa; the substrate temperature was 400 to 600.degree. C.; and the average output of ArF excimer laser was 5 to 40 W.
A diamond wheel is used for the polishing, and the grain size of a diamond abrasive grain is of about 0.25 .mu.m.
The etching treatment is carried out at room temperature. An alcohol solution containing 3 to 5% of nitric acid is used as an etching solution for the Fe deposit layer, and the immersion time is set in a range of 30 to 60 seconds. An aqueous solution containing 10% of sodium hydroxide and 10% of sodium ferricyanide is used as an etching solution for the Mo and W deposit layers, and the immersion time is set in a range of 15 to 60 seconds.
A specified example will be described below.
A deposit layer 50 formed of an aggregate of Fe crystals and having a thickness of 15 .mu.m was formed by subjecting outer peripheral surfaces of a land portion 20 and a skirt portion 21 of a piston body 19a made of an aluminum alloy (JIS AC8B-T7) to an electrolytic Fe plating process.
Table 31 shows the conditions for the electrolytic Fe plating process for examples 1a to 6a of the deposit layers. The plating time was varied within a range of 10 to 60 minutes in order to set the thickness of the examples 1a to 6a at 15.mu., as described above.
TABLE 31__________________________________________________________________________ Plating bath Ferrous Pulse current processDeposit sulfate Temperature CDmax CDm T.sub.ONLayer (g/liter) pH (.degree. C.) (A/dm.sup.2) (A/dm.sup.2) T.sub.ON /T.sub.C (msec)__________________________________________________________________________Example 1b 400 6.5 45 20 4 0.2 2Example 2b 400 6.5 42 20 4 0.2 2Example 3b 400 6.5 42 10 3 0.3 2Example 4b 400 6.5 42 10 3 0.3 2Example 5b 400 6.5 42 7 2 0.3 2Example 6b 400 6 50 8 4 0.5 2__________________________________________________________________________
Table 32 shows the crystal form of the deposit layer surface, the area rate A and grain size of the hexagonal pyramid-shaped Fe crystals in the deposit layer surface, the content of the oriented Fe crystals, and the hardness of a section of the deposit layer.
TABLE 32__________________________________________________________________________ Hexagonal pyramid-Crystal shaped Fe crystals Content S (%) of Hexagonal Hard-Deposit form of Area rate Grain pyramid-shaped Fe crystals nesslayer surface A (%) size (.mu.m) {110} {200} {211} {310} {222} HmV__________________________________________________________________________Example 1a Hexagonal 90 5-10 2.8 1.7 3.3 1.1 91.1 430 pyramid- shapedExample 2a Hexagonal 80 5-10 5.4 1.8 7.2 1.1 84.5 450 pyramid- shapedExample 3a Hexagonal 60 5-10 17.4 2.3 15.5 2.7 62.1 400 pyramid- shaped and block-likeExample 4a Hexagonal 40 5-10 18.4 8.6 17.9 9.5 45.6 370 pyramid- shaped and block-likeExample 5a Hexagonal 30 5-10 20.1 9 19.9 12.6 38.4 320 pyramid- shaped and block-likeExample 6a Granular 0 -- 18.6 20.4 17.2 21.5 22.3 250__________________________________________________________________________
The area rate A of the hexagonal pyramid-shaped Fe crystals was determined according to an equation, A=(c/b).times.100(%), as in the second embodiment, wherein b represents an area of the deposit layer surface, and c represents an area occupied by all the hexagonal pyramid-shaped Fe crystals in the surface. The grain size of the hexagonal pyramid-shaped Fe crystals is an average value of distances between opposed corners on the opposite sides of an apex, i.e., of lengths of three diagonal lines.
The content S was determined in the same manner as in the first embodiment, based on the X-ray diffraction patterns (X-ray was applied in a direction perpendicular to the deposit layer surface) for the examples 1a to 6a. FIG. 62 is the X-ray diffraction pattern for the example 1a.
FIG. 63 is a photomicrograph showing the crystal form of the surface in the example 1a, wherein a large number of hexagonal pyramid-shaped Fe crystals are observed. In this case, the area rate A of the hexagonal pyramid-shaped Fe crystals is equal to 90%, as shown in Table 32. Each of the hexagonal pyramid-shaped Fe crystals is a {222} oriented Fe crystal with its (hhh) plane, i.e., {222} plane oriented toward the surface. The content S of the {222} oriented Fe crystals is equal to 91.1%, as shown in Table 32 and FIG. 62.
FIG. 64 is a photomicrograph showing the crystal form of the surface in the example 3a, wherein a large number of hexagonal pyramid-shaped Fe crystals and a large number of block-like Fe crystals are observed.
Then, each of the surfaces of the examples 1a to 5a of the deposit layers was subjected to a polishing by a diamond wheel to form the hexagonal pyramid-shaped Fe crystals into truncated hexagonal pyramid-shaped Fe crystals, thereby providing examples 1b to 5b corresponding to the examples 1a to 5a, respectively. FIG. 65 is a photomicrograph showing the crystal form of the surface in the example 1b, wherein a top face of the truncated hexagonal pyramid-shaped Fe crystal is observed.
Thereafter, each of the examples 1b to 5b was subjected to an etching treatment, in which it was immersed for 30 seconds in an alcohol solution containing 5% of nitric acid at ambient temperature, thereby providing examples 1 to 5 of slide surface constructions corresponding to the examples 1b to 5b, respectively.
FIG. 66A is a photomicrograph showing the crystal form of a slide surface in the example 1, and FIG. 66B is a tracing of FIG. 66A. It is observed in FIGS. 66A and 66B that a top face of the truncated hexagonal pyramid-shaped Fe crystal 48 is comprised of six flat face portions 49a, 49b, 49c, 49d, 49e and 49f, so that the three protruding flat face portions 49a, 49c and 49e and the depressed flat face portions 49b, 49d and 49f are alternately located about an inner center o.
The reason why the protruding flat face portions and the depressed flat face portions appear on the top face is presumed as being in that the crystal defining one of the flat face portions and the crystal defining the other flat face portion form a twin crystal.
The step "s" was measured by vertically cutting the truncated hexagonal pyramid-shaped Fe crystal on a diagonal line L by use of a focus ion beam (FIM), as shown in FIG. 66B and then measuring the step "s" by use of a scanning electronic microscope (SEM). Thus, it was ascertained that the step "s" in the examples 1 to 5 was in a range of about 0.1 .mu.m to about 0.5 .mu.m.
Then, chips having the construction of examples 1 to 5, chips having the construction of examples 1b, 2b, 4b and 5b after being subjected to the polishing, and chips having the construction of example 6a of the deposit layer, were fabricated and subjected to a seizure test in a chip-on-disk manner under lubrication to measure the seizure generating load, thereby providing the results given in Table 33. The condition for the seizure test were as follows: the material for a disk was a cast iron (JIS FC250), the peripheral speed of the disk was 15 m/sec; the amount of oil supplied was 40 ml/min; the area of the slide surface of the chip was 10 mm.sup.2 ; and the load on the chip was increased at a rate of 50 N/min.
TABLE 33______________________________________ Seizure generating load (N)______________________________________Slide surface Example 1 2100construction Example 2 2000 Example 3 1800 Example 4 1600 Example 5 500After polishing Example 1b 1550 Example 2b 1500 Example 4b 1200 Example 5b 500Deposit layer Example 6a 300______________________________________
FIG. 67 shows the relationship between the area rate A of the truncated hexagonal pyramid-shaped Fe crystals and the seizure generating load for the examples 1 to 5, 1b, 2b, 4b, 5b and 6a. It can be seen from FIG. 67 that if the area rate A of the truncated hexagonal pyramid-shaped Fe crystals is set in a range of A.gtoreq.40% and the top face of the truncated hexagonal pyramid-shaped Fe crystal is comprised of six flat face portions having steps as described above, the slide surface construction exhibits an excellent seizure resistance, as shown by examples 1 to 4.
The examples 1b, 2b and 4b are inferior in seizure resistance to the examples 1, 2 and 4 due to the different structure of the top face. The example 5 and 5b are extremely low in seizure resistance due to the fact that the area rate of the truncated hexagonal pyramid-shaped Fe crystals is lower than 40%, and the example 6a is extremely low in seizure resistance due to the fact that the slide surface is formed of granular Fe crystals.
Then, the sliding test was carried out in the same chip-on-disk manner as that described above to measure the dynamic friction coefficient .mu. at the time when each of the examples 1 to 5, 1b, 2b, 4b, 5b and 6a generated a seizure, thereby providing the results given in Table 34.
TABLE 34______________________________________ Dynamic friction coefficient .mu.______________________________________Slide surface Example 1 0.008construction Example 2 0.008 Example 3 0.0085 Example 4 0.0085 Example 5 0.011After polishing Example 1b 0.009 Example 2b 0.009 Example 4b 0.01 Example 5b 0.011Deposit layer Example 6a 0.014______________________________________
FIG. 68 shows the relationship between the area rate A of the truncated hexagonal pyramid-shaped Fe crystals and the dynamic friction coefficient .mu. for the examples 1 to 5, 1b, 2b, 4b, 5b and 6a. It can be seen in FIG. 68 that if the area rate A of the truncated hexagonal pyramid-shaped Fe crystals is set in a range of A.gtoreq.40% and the top face of the truncated hexagonal pyramid-shaped Fe crystal is comprised of the six flat face portions having steps, the dynamic friction coefficient .mu. can be remarkably reduced, as in the examples 1 to 4.
The examples 1b, 2b and 4b are higher in dynamic friction coefficient .mu., as compared with the examples 1, 2 and 4, due to the different structure of the top face. In the examples 5 and 5b, the dynamic friction coefficient .mu. is increased due to the area rate of the truncated hexagonal pyramid-shaped Fe crystals being lower than 40%, and in the example 6a, the dynamic friction coefficient .mu. is remarkably high due to the fact that the slide surface is formed of granular Fe crystals.
The fourth embodiment is not limited to the piston for the internal combustion engine, and is applicable to various slide members such as a piston pin, a cam shaft, a piston ring, a balancer shaft and the like.

Number	Date	Country
7-099593	Mar 1995	JPX
7-099604	Mar 1995	JPX
7-099754	Mar 1995	JPX

Number	Name	Date
5322743	Fujisawa et al.	Jun 1994
5324596	Fujisawa et al.	Jun 1994
5401585	Fujisawa et al.	Mar 1995
5427633	Fujisawa et al.	Jun 1995
5445684	Gunji et al.	Aug 1995
5503942	Tabata	Apr 1996
5547771	Gunji et al.	Aug 1996

Number	Date	Country
670 402	Jan 1939	DEX
6174089	Jun 1994	JPX
2257759	Jan 1993	GBX
2273748	Jun 1994	GBX

Slide surface construction and process for producing the same

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Entry
Partial Translation of German Pat. No. 670,402 of Jan. 1939.
Search Report of GB Patent Office of May 24, 1996.