Slide surface construction

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 having a high hardness.
2. Description of the Related Art
One example of the conventionally known slide surface constructions of this type is a Fe deposit layer which is formed on an outer peripheral surface of a pipe-like substrate made of a steel in a piston pin for an internal combustion engine for the purpose of enhancing the wear resistance.
However, the known slide surface construction suffers 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 an oil retaining property, namely, oil retention and poor in seizure resistance due to a relatively smooth slide surface thereof.
Therefore, the present applicant has previously developed a slide surface construction including a large number of metal crystals in a slide surface thereof (for example, see Japanese Patent Application Laid-open No.174089/94).
If the slide surface construction is formed in this 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 fine swamps formed due to the mutual biting of the crests. Therefore, the slide surface construction has a good oil retention. Thus, the seizure resistance of the slide surface construction is enhanced.
However, as a result of various reviews of the slide surface construction, it has been made clear that the slide surface construction has a relatively low hardness and hence, in order to accommodate a more severe sliding environment, it is necessary to enhance the hardness of the slide surface construction and to inhibit the wearing of the pyramid-shaped metal crystals in the sliding environment to maintain the good oil retention of the slide surface construction.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a slide surface construction of the above-described type, which has a hardness high enough to meet the above demand.
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 of the slide surface construction is in a range of 40%.ltoreq.A.ltoreq.100%, and the content of cobalt (Co) in the aggregate is in a range of 13% by weight.ltoreq.Co.ltoreq.55% by weight.
If the area rate A of the pyramid-shaped metal crystals is set in such 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.
If the Co content is set in such range, the hardness of the slide surface construction can be remarkably enhanced, and the friction coefficient .mu. can be lowered.
In such slide surface construction, the wearing of the pyramid-shaped metal crystals is inhibited even if the slide surface construction is placed in a severe sliding environment. Therefore, under lubrication, the oil retention of the slide surface construction is maintained satisfactorily, and under non-lubrication, the dispersion of a sliding load is provided by the large number of fine pyramid-shaped metal crystals. Thus, the slide surface construction exhibits an excellent seizure resistance both under lubrication and under non-lubrication.
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 area rate A lower than 40% is undesirable. On the other hand, if the Co content is lower than 13% by weight, the metal crystals are liable to be granulated in the slide surface.
It is another object of the present invention to provide a slide surface construction of the above-described type, which has a high oil retention and the like and is capable of exhibiting an excellent sliding characteristic.
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%, and at least some of the pyramid-shaped metal crystals are heteromorphic pyramid-shaped metal crystals, each of which has at least one fine groove which is formed in at least a portion of at least one ridgeline-correspondence area and which extends in the same direction as the direction of extension of a ridgeline.
If the area rate A of the pyramid-shaped metal crystals is set in such 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. The intricateness is doubled by the existence of the heteromorphic pyramid-shaped metal crystals each having the fine groove as described above.
Even if such slide surface construction is placed in a severe sliding environment, it exhibits an excellent oil retention under lubrication. On the other hand, under non-lubrication, a sliding load dispersing effect is exhibited by the large number of fine pyramid-shaped metal crystals. Thus, the slide surface construction has an excellent seizure resistance both under lubrication and under non-lubrication.
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 area rate A lower than 40% is undesirable.
The above and other objects, features and advantages of the invention will become apparent from the following detailed description of preferred embodiments taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a broken-away perspective view of an essential portion of a piston pin;
FIG. 2 is a perspective view showing a body-centered cubic structure and its (hhh) plane and (2hhh) plane;
FIG. 3 is an enlarged sectional view taken along a line 3--3 in FIG.1;
FIG. 4 is a view taken in the direction of an arrow 4 in FIG.3;
FIG. 5A is a schematic plan view showing a first example of a heteromorphic hexagonal pyramid-shaped metal crystal;
FIG. 5B is a schematic plan view showing one example of a normal hexagonal pyramid-shaped metal crystal;
FIGS. 6A, 6B, 6C and 6D show various forms of heteromorphic hexagonal pyramid-shaped metal crystals, with FIG. 6A being a schematic plan view of a second example of the heteromorphic hexagonal pyramid-shaped metal crystal, FIGS. 6B and 6C being schematic side views of third and fourth examples of the heteromorphic hexagonal pyramid-shaped metal crystals, respectively, and FIG. 6D being a sectional view taken along a line 6D--6D in FIG. 6C;
FIG. 7 is a plan view of a normal trigonal pyramid-shaped metal crystal;
FIG. 8 is a diagram showing the inclination of the (hhh) plane of the body-centered cubic structure;
FIG. 9 is a wave form of an output from a power source for an electrolytic plating;
FIG. 10 is an X-ray diffraction pattern for an example 4 of a slide surface construction;
FIG. 11 is a photomicrograph showing the crystal form of an example 1 of a slide surface;
FIG. 12 is a photomicrograph showing the crystal form of an example 4 of the slide surface;
FIG. 13A is a photomicrograph showing the crystal form of an example 5 of the slide surface;
FIG. 13B is an enlarged photomicrograph taken from FIG. 13A;
FIG. 14 is a graph illustrating the relationship between the Co content and the hardness;
FIG. 15 is a graph illustrating the relationship between the Co content and the area rate B of heteromorphic hexagonal pyramid-shaped Fe-Co ordered alloy crystals;
FIG. 16 is a graph illustrating the relationship between the area rate A of hexagonal pyramid-shaped Fe-Co ordered alloy crystals and the seizure generating load;
FIG. 17 is a graph illustrating the relationship between the area rate A of hexagonal pyramid-shaped Fe-Co ordered alloy crystals and the friction coefficient .mu.; and
FIG. 18 is a graph illustrating the relationship between the Co content and the friction coefficient .mu..

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1, a piston pin 1 for an internal combustion engine includes a pipe-like substrate made of a steel. A lamellar slide surface construction 4 is formed on an outer peripheral surface 3 of the substrate 2 by plating.
The slide surface construction 4 is formed of an aggregate of metal crystals, such as Fe (ferrous)-Co (cobalt) crystals, having a body-centered cubic structure (which will be also referred to as a bcc structure hereinafter) in the embodiment, as shown in FIG. 2. The content of cobalt (Co) in the aggregate is set in a range of 13% by weight.ltoreq.Co.ltoreq.55% by weight. The aggregate includes at least one of a large number of (hhh) oriented metal crystals 5 which are grown into a columnar shape from the substrate 2 with their (hhh) planes (by Miller indices) oriented toward a slide surface 4a, or a large number of (2hhh) oriented metal crystals which are grown into a columnar shape from the substrate 2 with their (2hhh) planes (by Miller indices) oriented toward the slide surface 4a.
When the aggregate of the metal crystals having the bcc structure as described above includes the large number of (hhh) oriented metal crystals 5 with their (hhh) planes (by Miller indices) oriented toward the slide surface 4a, tip ends of the (hhh) oriented metal crystals 5 can be formed into hexagonal pyramid-shaped metal crystals (pyramid-shaped metal crystals) 6 in the slide surface 4a, as shown in FIG. 4.
At least some of the hexagonal pyramid-shaped metal crystals 6 are heteromorphic hexagonal pyramid-shaped metal crystals (heteromorphic pyramid-shaped metal crystals) 7, as shown in FIGS. 4 and 5A. Each of the heteromorphic hexagonal pyramid-shaped metal crystals 7 has at least one (one, in the illustrated embodiment) fine groove 8 which extends in the same direction as a direction of extension of a ridgeline over at least a portion, e.g., the substantially entire length of each of at least one (six, in the illustrated embodiment) ridgeline-correspondence areas R.sub.1.
The heteromorphic hexagonal pyramid-shaped metal crystal 7 has at least one (six, in the illustrated embodiment) slope-correspondence areas R.sub.2 each formed in a V-shaped groove 9 with its opening width gradually decreased from a skirt portion toward an apex.
Normal hexagonal pyramid-shaped metal crystals 10 having no fine grooves 8 in ridgelines r as clearly shown in FIGS. 4 and 5B are included in the hexagonal pyramid-shaped metal crystals 6. In the normal hexagonal pyramid-shaped metal crystal 10, at least one slope p thereof may be likewise formed in a V-shaped groove 9.
In addition to the above-described form of the heteromorphic hexagonal pyramid-shaped metal crystals 7, various forms are included in the heteromorphic hexagonal pyramid-shaped metal crystals 7, as shown in FIG. 6A to 6D. FIG. 6A shows the form in which ridgelines r and ridgeline-correspondence areas R.sub.1 are alternately disposed, and a fine groove 8 exists in each ridgeline-correspondence area R.sub.1. FIG. 6B shows the form in which a fine groove 8 exists in a portion of each ridgeline-correspondence area R.sub.1. FIG. 6c and 6D show the form in which two fine grooves 8 exist in one ridgeline-correspondence area R.sub.1. At least one slope-correspondence area R.sub.2 may be formed in a V-shaped groove 9.
Normal trigonal pyramid-shaped metal crystals 11 shown in FIG. 7 and heteromorphic trigonal pyramid-shaped metal crystals (not shown) are included in the trigonal pyramid-shaped metal crystals which are (hhh) oriented metal crystals.
The hexagonal pyramid-shaped metal crystals 6 are small in average grain size and substantially uniform in grain sizes, as compared with the trigonal pyramid-shaped metal crystals. In the hexagonal pyramid-shaped metal crystals 6 and the like, there is an interrelation between the grain size and the height. Therefore, the fact that the grain sizes are substantially uniform, indicates that the heights are also substantially equal to one another.
When the aggregate of the metal crystals having the bcc structure includes a large number of (2hhh) oriented metal crystals with their (2hhh) planes (by Miller indices) oriented toward the slide surface 4a, normal small pyramid-shaped metal crystals and heteromorphic small pyramid-shaped metal crystals are included in the pyramid-shaped metal crystals.
The area rate A of the pyramid-shaped metal crystals such as the normal hexagonal, trigonal and small pyramid-shaped metal crystals and the heteromorphic hexagonal, trigonal and small pyramid-shaped metal crystals in the slide surface 4a is set in a range of 40%.ltoreq.A.ltoreq.100%.
If the area rate A is set in such range, for example, adjacent ones of the hexagonal pyramid-shaped metal crystals assume mutually biting states. Thus, the slide surface 4a has an increased surface area, as compared with the slide surface formed of the trigonal pyramid-shaped metal crystals, and takes on a very intricate aspect comprising a large number of extremely fine crests 12, a large number of extremely fine valleys 13 formed between the crests 12, and a large number of extremely fine swamps 14 formed due to the mutual biting of the crests 12. The intricateness is doubled by the existence of the heteromorphic hexagonal pyramid-shaped metal crystals having the fine grooves 8 and the V-shaped grooves 9.
Moreover, the content of cobalt (Co) in the aggregate is set in the above-described range, the hardness of the slide surface construction 4 can be remarkably enhanced, and the friction coefficient .mu. can be lowered.
In such slide surface construction 4, the wearing of the hexagonal pyramid-shaped metal crystals 6 is inhibited even if the slide surface construction 4 is placed in a severe sliding environment. Therefore, under lubrication, the oil retention of the slide surface construction 4 is maintained, and under non-lubrication, the dispersion of a sliding load is provided by the hexagonal pyramid-shaped metal crystals 6. Thus, the slide surface construction 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 6, a local increase in surface pressure can be avoided and a fine division of the sliding load can be achieved. This also lowers the friction coefficient .mu. and hence, in cooperation with the presence of cobalt (Co), the slide surface construction 4 exhibits an excellent wear resistance not only under lubrication but also under non-lubrication.
As shown in FIG. 8, the inclination of the (hhh) plane with respect to a phantom plane 15 along the slide surface 4a appears as the inclination of the hexagonal pyramid-shaped metal crystals 6 and the like and hence, an influence is imparted to the oil retention and the wear resistance of the slide surface construction 4. The inclination angle .theta. formed by the (hhh) plane with respect to the phantom plane 15 is set in a range of 0.degree..ltoreq..theta..ltoreq.15.degree.. 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 4 are reduced. The inclination angle .theta. also applies to the (2hhh) plane.
The slide surface construction 4 is formed of an aggregate of binary alloy crystals, e.g., Fe-Co ordered alloy crystals forming an ordered lattice of CuZn type (L2 type) which is of a CsCl type structure (bcc structure). In this case, it is believed that heteromorphic hexagonal pyramid-shaped Fe-Co ordered alloy crystals are formed by the concentration of ordered lattices of Fe and Co in the ridgeline-correspondence area R.sub.1 which is highest in energy during a plating treatment.
In addition to the Fe-Co ordered alloy, examples of the binary alloys are Cu-Zn, Fe-V, Ag-Zn, Ag-Cd, Au-Mn and Cu-Pd ordered alloys and the like.
In the plating treatment for forming the slide surface construction 4, conditions for a plating bath in forming the aggregate of the Fe-Co ordered alloy crystals by an electrolytic plating process are as shown in Table 1.
TABLE 1______________________________________Composition (g/liter) Co- Tempera-Ferrous Boric Ammonium containing turesulfate acid sulfate additive ph (.degree. C.)______________________________________100-400 0-50 0-200 .ltoreq.450 3-6.5 10-60______________________________________
Examples of the Co-containing additive which may be used are substances containing cobalt and soluble in water, such as cobalt sulfate, cobalt ammonium sulfate, cobalt chloride, cobalt borofluoride and the like.
A pulse current process is mainly utilized as an energizing process. 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 electric 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.
If the energization time period from the start of the increasing of the electric current I to the start of the dropping thereof is represented by T.sub.ON, and a cycle time period is represented by T.sub.C, wherein one cycle is defined as being from the start of the preceding increasing of the electric current to the start of the succeeding increasing thereof, as shown in FIG. 9, the ratio of the energization time period T.sub.ON to the cycle time period 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 average cathode current density CDm is set in a range of CDm.gtoreq.2 A/dm.sup.2.
If such a pulse current process is utilized, the ion concentration in the vicinity of a cathode is unformized due to the fact that the electric current flows or does not flow within the plating bath. Thus, the composition of the slide surface construction 4 can be stabilized.
The precipitation, content (which indicates a presence amount) and the like of the (hhh) oriented Fe-Co ordered alloy crystals or the (2hhh) oriented Fe-Co ordered alloy crystals are controlled by changing the plating conditions and the energizing conditions. This control is easy under the utilization of the pulse current process and hence, the slide surface 4a is easily formed into an intended form. In order to accurately control the content of cobalt (Co) in the slide surface construction 4 and to uniformly disperse the cobalt (Co), a liquid replenisher adjusted to the same composition and the same temperature as those of the plating bath is supplied in a predetermined amount between the anode and the cathode during the electrolytic plating. If this supplying is not conducted, a variability in concentration of the Co-containing additive in the plating bath is produced and for this reason, it is difficult to control the content of cobalt (Co) in the slide surface construction 4.
The content of cobalt (Co) in the slide surface construction 4 is controlled basically by the concentration of the Co-containing additive in the plating bath. However, if the composition, pH and temperature of the plating bath are constant, the Co content is controlled by the maximum cathode current density CDmax and the average cathode current density CDm.
In addition to the electrolytic plating, other examples of the plating process are a PVD process, a CVD process, a sputtering process, an ion plating, which are gas-phase plating processes. Conditions for carrying out a Fe-Co alloy plating by a sputtering process are as follows: the Ar gas pressure is 0.2 to 1.0 Pa; the average Ar gas accelerating electric power is D.C. 0.1 to 1.5 kW; and the substrate temperature is 80 to 300.degree. C. In this case, a Fe-Co alloy or a Fe or Co simple metal is used as a cathode target.
Particular examples will be described below.
A plurality of piston pins 1 for an internal combustion engine were produced by subjecting an outer peripheral surface 3 of a pipe-like substrate 2 made of chromemolybdenum steel (JIS SCM420) to an electrolytic plating process to form a slide surface construction 4 formed of an aggregate of Fe-Co ordered alloy crystals and having a thickness of 15 .mu.m on the outer peripheral surface 3.
Tables 2, 3, 4 and 5 show conditions for the electrolytic plating process for examples 1 to 20, with FIG. 2 corresponding to the examples 1 to 5; Table 3 corresponding to the examples 6 to 10; Table 4 corresponding to the examples 11 to 15; and table 5 corresponding to the examples 16 to 20. The plating time was varied to various values within a range of 5 to 60 minutes in order to set the thickness for the examples 1 to 20 at 15 .mu.m, as described above. The amount of liquid replenisher supplied was set at 0.5 liter/min.
TABLE 2__________________________________________________________________________Plating bathFerrous Cobalt Pulse current processSlide surface sulfate sulfate Temperature CDmax CDm T.sub.ONconstruction (g/liter) (g/liter) pH (.degree.C.) (A/dm.sup.2) (A/dm.sup.2) T.sub.ON T.sub.C (msec)__________________________________________________________________________Example 1 400 100 6 50 10 2 0.2 2Example 2 100 15 3Example 3 150 15 3Example 4 200 20 4Example 5 300 25 5__________________________________________________________________________
TABLE 3__________________________________________________________________________Plating bathFerrous Cobalt Pulse current processSlide surface sulfate sulfate Temperature CDmax CDm T.sub.ONconstruction (g/liter) (g/liter) pH (.degree.C.) (A/dm.sup.2) (A/dm.sup.2) T.sub.ON T.sub.C (msec)__________________________________________________________________________Example 6 300 100 6 50 10 2 0.2 2Example 7 100 15 3Example 8 150 15 3Example 9 200 20 4Example 10 300 25 5__________________________________________________________________________
TABLE 4__________________________________________________________________________Plating bathFerrous Cobalt Pulse current processSlide surface sulfate sulfate Temperature CDmax CDm T.sub.ONconstruction (g/liter) (g/liter) pH (.degree.C.) (A/dm.sup.2) (A/dm.sup.2) T.sub.ON T.sub.C (msec)__________________________________________________________________________Example 11 200 100 6 50 10 2 0.2 2Example 12 100 15 3Example 13 150 15 3Example 14 200 20 4Example 15 300 25 5__________________________________________________________________________
TABLE 5__________________________________________________________________________Plating bathFerrous Cobalt Pulse current processSlide surface sulfate sulfate Temperature CDmax CDm T.sub.ONconstruction (g/liter) (g/liter) pH (.degree. C.) (A/dm.sup.2) (A/dm.sup.2) T.sub.ON T.sub.C (msec)__________________________________________________________________________Example 16 100 50 6 50 10 2 0.2 2Example 17 50 15 5Example 18 75 15 3Example 19 100 20 4Example 20 100 25 5__________________________________________________________________________
Table 6 shows the content S of the oriented Fe-Co ordered alloy crystals in the examples 1 to 10, and Table 7 shows the content S of the oriented Fe-Co ordered alloy crystals in the examples 11 to 20.
TABLE 6______________________________________Slide Content S (%) of oriented Fe--Co ordered alloysurface crystalsconstruction {110} {200} {211} {310} {222}______________________________________Example 1 0.5 0 5.5 0 94Example 2 1 0.5 6 0 92.5Example 3 0.5 0 9 0 90.5Example 4 0 0.5 8.5 0 91Example 5 0 0.4 9.2 0 90.4Example 6 10.5 9 13.2 7 60.3Example 7 11.2 8.8 13.3 5.3 61.4Example 8 10.9 8.7 12.6 7.1 60.7Example 9 11.8 10.4 11.9 5.3 60.6Example 10 11.7 9.2 12.7 5.2 61.2______________________________________
TABLE 7______________________________________Slide Content S (%) of oriented Fe--Co ordered alloysurface crystalsconstruction {110} {200} {211} {310} {222}______________________________________Example 11 24 5.1 26.9 1.8 42.2Example 12 23.1 3.5 30.1 2.5 40.8Example 13 24.4 0.9 28.4 4.8 41.5Example 14 21.3 1.2 27.6 8.2 41.7Example 15 22.5 2.8 29 4.8 40.9Example 16 22.3 10.5 24.2 8.2 34.8Example 17 21.5 11.4 23.1 10.1 33.9Example 18 24.8 12.1 22.7 6 34.4Example 19 20.9 12.9 22.8 8.7 34.7Example 20 21.8 11.8 24.5 7.7 34.2______________________________________
The content S of the oriented Fe-Co ordered alloy crystals was determined from the following equation, based on X-ray diffraction patterns (X-ray was applied in a direction perpendicular to the slide surface) for the examples 1 to 20. The X-ray diffraction pattern for the example 4 is shown as one example in FIG. 10. For example, the {110} oriented alloy crystal means an oriented Fe-Co ordered alloy crystal with its
{110} plane oriented toward the slide surface 4a.
{110} Oriented Fe-Co ordered alloy crystal:
S.sub.110 ={(I.sub.110 /IA.sub.110)/T}.times.100
{200} Oriented Fe-Co ordered alloy crystal:
S.sub.200 ={(I.sub.200 /IA.sub.200)/T}.times.100
{211} Oriented Fe-Co ordered alloy crystal:
S.sub.211 ={(I.sub.211 /IA.sub.211)/T}.times.100
{310} Oriented Fe-Co ordered alloy crystal:
S.sub.310 ={(I.sub.310 /IA.sub.310)/T}.times.100
{222} Oriented Fe-Co ordered alloy crystal:
S.sub.222 ={(I.sub.222 /IA.sub.222)/T}.times.100
wherein each of I.sub.110, I.sub.200, I210, I310 and I.sub.222 is a measurement (cps) of an intensity of X-ray reflected from each crystal plane, and each of IA.sub.110, IA.sub.200, IA.sub.210, 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)
Tables 8, 9, 10 and 11 show the Co content, the crystal form of the slide surface, the area rate A and grain size of the hexagonal pyramid-shaped Fe-Co ordered alloy crystals in the slide surface, the area rate B of the heteromorphic hexagonal pyramid-shaped Fe-Co ordered alloy crystals in the slide surface, the ratio B/A of the area rate B to the area rate A, and the hardness of a section of the slide surface construction for the examples 1 to 20, with Table 8 corresponding to the examples 1 to 5; Table 9 corresponding to the examples 6 to 10; Table 10 corresponding to the examples 11 to 15; Table 11 corresponding to the examples 16 to 20.
TABLE 8__________________________________________________________________________ Area rate B (%) Hexagonal pyramid- heteromorphic Co shaped Fe--Co ordered hexagonalSlide content Crystal form alloy crystals pyramid-shapedsurface (% by of slide Area rate Grain Fe--Co ordered Ratio Hardnessconstruction weight) surface A (%) size (.mu.m) alloy crystals B/A HmV__________________________________________________________________________Example 1 0.5 Normal 100 0.5-6 0 0 210 hexagonal pyramid- shapedExample 2 12 Normal 0.5-6 5 0.05 220 hexagonal pyramid-Example 3 13 shaped and 0.5-5 10 0.1 380 heteromorphic hexagonalExample 4 26 pyramid- 0.5-3 60 0.6 410 shapedExample 5 40 Heteromorphic 0.5-3 100 1 430 hexagonal pyramid- shaped__________________________________________________________________________
TABLE 9__________________________________________________________________________ Area rate B (%) Hexagonal pyramid- heteromorphic Co shaped Fe--Co ordered hexagonalSlide content Crystal form alloy crystals pyramid-shapedsurface (% by of slide Area rate Grain Fe--Co ordered Ratio Hardnessconstruction weight) surface A (%) size (.mu.m) alloy crystals B/A HmV__________________________________________________________________________Example 6 0.5 Normal 60 0.5-6 0 0 200 hexagonal pyramid- shaped and normal small pyramid-shapedExample 7 12 Normal 0.5-6 3 0.05 210 hexagonal pyramid-Example 8 13 heteromorphic 0.5-5 6 0.1 360 hexagonal pyramid-Example 9 26 shaped and 0.5-5 36 0.6 390 normal small pyramid-shapedExample 10 40 Heteromorphic 0.5-3 60 1 420 hexagonal pyramid- shaped and normal small pyramid-shaped__________________________________________________________________________
TABLE 10__________________________________________________________________________ Area rate B (%) Hexagonal pyramid- heteromorphic Co shaped Fe--Co ordered hexagonalSlide content Crystal form alloy crystals pyramid-shapedsurface (% by of slide Area rate Grain Fe--Co ordered Ratio Hardnessconstruction weight) surface A (%) size (.mu.m) alloy crystals B/A HmV__________________________________________________________________________Example 11 0.5 Normal 40 0.5-6 0 0 200 hexagonal pyramid- shaped and normal small pyramid-shapedExample 12 12 Normal 0.5-6 2 0.05 220 hexagonal pyramid- shaped,Example 13 13 heteromorphic 0.5-6 4 0.1 350 hexagonal pyramid-Example 14 26 shaped and 0.5-6 24 0.6 390 normal small pyramid-shapedExample 15 40 Heteromorphic 0.5-6 40 1 420 hexagonal pyramid- shaped and normal small pyramid-shaped__________________________________________________________________________
TABLE 11__________________________________________________________________________ Area rate B (%) Hexagonal pyramid- heteromorphic Co shaped Fe--Co ordered hexagonalSlide content Crystal form alloy crystals pyramid-shapedsurface (% by of slide Area rate Grain Fe--Co ordered Ratio Hardnessconstruction weight) surface A (%) size (.mu.m) alloy crystals B/A HmV__________________________________________________________________________Example 16 0.5 Normal 35 0.5-7 0 0 220 hexagonal pyramid- shaped and granularExample 17 12 Normal 0.5-7 2 0.05 230 hexagonal pyramid-Example 18 13 shaped, 0.5-7 4 0.1 340 heteromorphic hexagonalExample 19 26 pyramid- shaped and 0.5-7 21 0.6 350 granularExample 20 40 Heteromorphic 0.5-7 35 1 360 hexagonal pyramid- shaped and granular__________________________________________________________________________
The measurement of the Co content was carried out by a procedure which comprises peeling-off each of the examples 1 to 20 from the substrate 2 and then subjecting each example to an analysis according to a nitroso R salt absorptiometry (JIS G1222).
The area rate A of the hexagonal pyramid-shaped Fe-Co ordered alloy 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 hexagonal pyramid-shaped Fe-Co ordered alloy crystals in the slide surface. The grain size of the hexagonal pyramid-shaped Fe-Co ordered alloy crystals is an average value of distances between opposed corners on the opposite sides of an apex of each of the hexagonal pyramid-shaped Fe-Co ordered alloy crystals, i.e., of three distances. The area rate B of the heteromorphic hexagonal pyramid-shaped Fe-Co ordered alloy crystals was determined according to an equation, B=(d/b).times.100 (%), wherein b represents an area of the slide surface, and d represents an area occupied by all the heteromorphic hexagonal pyramid-shaped Fe-Co ordered alloy crystals in the slide surface.
FIG. 11 is a photomicrograph showing the crystal structure of the slide surface in the example 1, wherein a large number of normal hexagonal pyramid-shaped Fe-Co ordered alloy crystals are observed. In this case, the area rate A of the hexagonal pyramid-shaped Fe-Co ordered alloy crystals is equal to 100%, and the area rate B of the heteromorphic hexagonal pyramid-shaped Fe-Co ordered alloy crystals is equal to 0%, as shown in Table 8, and hence, only the normal hexagonal pyramid-shaped Fe-Co ordered alloy crystals exist in the slide surface. Each of the normal hexagonal pyramid-shaped Fe-Co ordered alloy crystals is a {222} oriented Fe-Co ordered alloy crystal with its (hhh) plane, i.e., {222} plane oriented toward the slide surface. The content S of these {222} oriented Fe-Co ordered alloy crystals is equal to 94%, as shown in Table 6.
FIG. 12 is a photomicrograph showing the crystal structure of the slide surface in the example 4, wherein a large number of normal hexagonal pyramid-shaped Fe-Co ordered alloy crystals and a large number of heteromorphic hexagonal pyramid-shaped Fe-Co ordered alloy crystals are observed. In this case, the area rate A of the hexagonal pyramid-shaped Fe-Co ordered alloy crystals is equal to 100%, and the area rate B of the heteromorphic hexagonal pyramid-shaped Fe-Co ordered alloy crystals is equal to 60%, as shown in Table 8. Each of the normal and heteromorphic hexagonal pyramid-shaped Fe-Co ordered alloy crystals is likewise a {222} oriented Fe-Co ordered alloy crystal. The content S of these {222} oriented Fe-Co ordered alloy crystals is equal to 91%, as shown in Table 6 and FIG. 10.
FIGS. 13A and 13B are photomicrographs showing the crystal structure of the slide surface in the example 5, wherein a large number of heteromorphic hexagonal pyramid-shaped Fe-Co ordered alloy crystals are observed. In this case, the area rate A of the hexagonal pyramid-shaped Fe-Co ordered alloy crystals is equal to 100%, and the area rate B of the heteromorphic hexagonal pyramid-shaped Fe-Co ordered alloy crystals is equal to 100%, as shown in Table 8, and hence, only the heteromorphic hexagonal pyramid-shaped Fe-Co ordered alloy crystals exist in the slide surface. Each of the heteromorphic hexagonal pyramid-shaped Fe-Co ordered alloy crystals is likewise a {222} oriented Fe-Co ordered alloy crystal. The content S of these {222} oriented Fe-Co ordered alloy crystals is equal to 90.4%, as shown in Table 6.
FIG. 14 is a graph illustrating the relationship between the Co content and the hardness for the examples 1 to 5. In FIG. 14, points (1) to (5) correspond to the examples 1 to 5, respectively. This relationship between the points and the examples applies to Figures which will be described hereinafter. It can be seen from FIG. 14 that if the Co content is set in a range of Co.gtoreq.13% by weight, the hardness is suddenly increased. The same is true of the examples 6 to 20.
FIG. 15 shows the relationship between the Co content and the area rate B of the heteromorphic hexagonal pyramid-shaped Fe-Co ordered alloy crystals by the area rate A of the hexagonal pyramid-shaped Fe-Co ordered alloy crystals for the examples 1 to 20. It can be seen from FIG. 15 that when the Co content is in the range of Co.gtoreq.13% by weight, the area rate B of the heteromorphic hexagonal pyramid-shaped Fe-Co ordered alloy crystals is increased.
Then, chips having the structures of examples 1 to 20 were fabricated and subjected to a sliding test in a chip-on-disk manner under lubrication to measure the seizure generating load and the friction coefficient .mu., thereby providing results given in Table 12. Conditions for the sliding test were as follows: the material for the disk was Al-Si (Si 10% by weight) alloy; the peripheral speed of the disk was 15 m/sec; the amount of oil supplied was 0.3 ml/min; the area of the slide surface of the chip was 1 cm.sup.2 ; and the friction coefficient .mu. was a value provided when the pressing load on the chip was 250N.
TABLE 12______________________________________Slide surface Seizure generating Frictionconstruction load (N) coefficient .mu.______________________________________Example 1 1200 0.01Example 2 1350 0.0095Example 3 2100 0.006Example 4 2400 0.0055Example 5 2550 0.005Example 6 1050 0.011Example 7 1200 0.0105Example 8 1900 0.007Example 9 2100 0.0065Example 10 2200 0.006Example 11 900 0.012Example 12 1000 0.0115Example 13 1650 0.008Example 14 1850 0.0075Example 15 1900 0.007Example 16 280 0.018Example 17 330 0.0175Example 18 370 0.0173Example 19 400 0.017Example 20 430 0.017______________________________________
FIG. 16 shows the relationship between the area rate A of the hexagonal pyramid-shaped Fe-Co ordered alloy crystals and the seizure generating load by the Co content and the ratio B/A of the area rate B and the area rate A for the examples 1 to 20. FIG. 17 shows the relationship between the area rate A of the hexagonal pyramid-shaped Fe-Co ordered alloy crystals and the friction coefficient .mu. by the Co content and the ratio B/A of the area rate B and the area rate A for the examples 1 to 20.
It can be seen from FIGS. 16 and 17 that the examples 2 to 5, 7 to 10 and 12 to 15 having the area rate A of the pyramid-shaped Fe-Co ordered alloy crystals in the range of A.gtoreq.40% and including the heteromorphic hexagonal pyramid-shaped Fe-Co ordered alloy crystals are high in seizure generating load and low in friction coefficient .mu., as compared with the examples 1, 6, 11, and 16 to 20. Thus, each of the examples 2 to 5, 7 to 10 and 12 to 15 has a good seizure resistance and a good wear resistance. In this case, each of the examples 3 to 5, 8 to 10 and 13 to 15 having the Co content set in the range of Co.gtoreq.13% by weight and the area rate A in the range of A.gtoreq.40% and the ratio B/A of the area rate B to the area rate A set in the range of B/A.gtoreq.0.1 has remarkably excellent seizure and wear resistances, as compared with the examples 2, 7 and 12 having the ratio B/A smaller than 0.1 and Co content in the range of Co.gtoreq.13% by weight.
FIG. 18 shows the relationship between the Co content and the friction coefficient .mu. by the area rate A for the examples 1 to 20.
As apparent from FIG. 18, the examples 3 to 5, 8 to 10 and 13 to 15 having the area rate A in the range of A.gtoreq.40% and the Co content in the range of Co.gtoreq.13% by weight are low in friction coefficient .mu., as compared with the examples 1, 2, 6, 8, 11, 12 and 16 to 20 having the area rate A lower than 40% and/or the Co content lower than 13% by weight.
The present invention is not limited to the piston pin and is applicable to various slide members such as a piston, a cam shaft, a piston ring and the like.

Number	Date	Country	Kind
7-099592	Mar 1995	JPX
7-100484	Mar 1995	JPX

Number	Name	Date
5310606	Fujisawa et al.	May 1994
5324596	Fujisawa et al.	Jun 1994
5503942	Tabata et al.	Apr 1996

Slide surface construction

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