Patent Application
20090308507
The present invention relates to a Ni-based compound superalloy having excellent oxidation resistance, which has a multi-phase microstructure including a primary L12 phase and an eutectoid microstructure (L12 phase+D0x phase (including D022 phase, D024 phase, or D0a phase)). The present invention further relates to a method for manufacturing the aforementioned Ni-based compound superalloy.
This application claims priority from Japanese Patent Application No. 2006-261569, filed on Sep. 26, 2006, the content of which is incorporated herein by reference.
Nowadays, most high-temperature structural materials for turbine components of jet engines or gas turbines are Ni-based superalloys. Because at least approximately 35 vol % or more of the constituent phases of Ni-based superalloy are metal phases (γ), there are limitations in melting point and high-temperature creep strength of Ni-based superalloys. As candidates for high-temperature structural materials that surpass the Ni-based superalloys, high-temperature structural materials including intermetallic compounds in which the yield stress shows positive temperature dependence can be raised. However, single-phase materials have drawbacks of poor ductility at room temperature and low creep strength at high temperature. As to multi-phase materials compared with single-phase materials, because any of Ni3X type intermetallic compounds has a GCP (Geometrically Close Packed) crystal structure, there is a possibility that some of these intermetallic compounds may be combined with high coherency. Since there are a number of Ni3X type intermetallic compounds that have superior properties, by forming Ni3X type intermetallic compounds in the form of a multi-phase material, a new type of multi-phase intermetallic compounds, that is, multi intermetallics, having further excellent properties and a high freedom for microstructural control are expected to be produced.
It was previously reported that an attempt has been made to develop a multi-phase compound using a Ni3Al(L12)-Ni3Ti(D024)-Ni3Nb(D0a) system, and an alloy having superior properties could be developed (see Non-Patent Document 1). (Non-Patent Document 1)
K. Tomihisa, Y. Kaneno, T. Takasugi, Intermetallics, 10 (2002) 247
The aforementioned Ni-based superalloys are employed as structural materials for engines and the like where high-temperature heat resistance is required. In engines where this type of material is applied, the engine efficiency is influenced by the operating temperature and the engine weight. The density of the aforementioned Ni-based superalloy is 8.0 to 9.0 g/cm3, which is relatively heavy. Accordingly, there has been progress in the development of a Ni-based compound superalloy that has a slightly lighter specific gravity than that of the aforementioned Ni-based superalloy.
With this in mind, the present inventors carried out research and development with the goal of developing a superalloy having even more superior properties than these conventional Ni-based superalloys. As one aspect of these efforts, the present inventors carried out research and development of a Ni-based compound superalloy which includes Al in the amount of 5 to 13 at %, V in the amount of 9.5 to 17.5 at %, Ti in the amount of 0 to 3.5 at %, B in the amount of 1000 ppm (weight) or less, and Ni as the remainder, and has a dual multi-phase microstructure including a primary L12 phase and an (L12 phase+D022 phase) eutectoid microstructure.
The density of this Ni-based compound superalloy is in the range of 7.5 to 8.5 g/cm3, and is lighter in weight than the previously mentioned Ni-based superalloy. This Ni-based compound superalloy also has roughly the same high-temperature strength at temperatures up to around 1 000° C. as the aforemented Ni-based superalloy.
However, the aforementioned Ni-based compound superalloy is problematic in that its oxidation resistance is inferior.
In order to solve the aforementioned problems, the present invention aims to provide a Ni-based compound superalloy that is lighter in weight than the Ni-based superalloy, has roughly the same high-temperature strength at temperatures up to around 1000° C. as the Ni-based superalloy, and, moreover, has superior resistance to oxidation.
The present invention employs the following design to achieve the above aims.
The present invention provides a Ni-based compound superalloy which includes: Al: more than 5 at % to 13 at % or less; V: 3 at % or more to 9.5 at % or less; and Ti: 0 at % or more to 3.5 at % or less, with the remainder being Ni and unavoidable impurities, and has a multi-phase microstructure including a primary L12 phase and an (L12 phase+D022 phase and/or D024 and/or D0a phase) eutectoid microstructure. As a result, the Ni-based compound superalloy according to the present invention has a specific gravity that is slightly less than that of the conventional Ni-based superalloy, superior high-temperature strength at temperatures up to around 1000° C. that is on par with the Ni-based superalloy, and superior resistance to oxidation.
The manufacturing method according to the present invention enables the manufacturing of a Ni-based compound superalloy having a multi-phase microstructure including a primary L12 phase and an (L12 phase+D022 phase and/or D024 and/or D0a phase) eutectoid microstructure, this Ni-based compound superalloy has a specific gravity that is slightly less than that of the conventional Ni-based superalloy, a superior high-temperature strength at temperatures up to around 1273 K (1000° C.) that is on par with a Ni-based superalloy, and superior resistance to oxidation.
Embodiments of the present invention will now be explained using the accompanying figures. However, the present invention is not limited to the various embodiments explained below.
The Ni-based compound superalloy according to the present invention includes: Al: more than 5 at % to 13 at % or less; V: 3 at % or more to 9.5 at % or less; and Ti: 0 at % or more to 3.5 at % or less, with the remainder being Ni and unavoidable impurities, wherein the amount of V is not less than the amount of Nb, and the Ni-based compound superalloy has a multi-phase microstructure including a primary L12 phase and an (L12 phase+D022 phase and/or D024 and/or D0a phase) eutectoid microstructure.
The Ni-based compound superalloy according to the present invention may include Co: 15 at % or less in addition to the above composition, and may include Cr: 5 at % or less in addition to the above composition, and also may include B: 1000 ppm (weight) or less in addition to the above composition. Further, in addition to the above composition, it is preferable that the Ni-based compound superalloy according to the present invention has a multi-phase microstructure including a primary L12 phase and an (L12 phase+D022 phase and/or D024 and/or D0a phase) eutectoid microstructure, and it is most preferable that the Ni-based compound superalloy according to the present invention has a dual multi-phase microstructure composed of a primary L12 phase and an (L12 phase+D022 phase and/or D024 and/or D0a phase) eutectoid microstructure.
The thus-described Ni-based compound superalloy can be manufactured by the method which includes: melting an alloy material having a composition that includes: Al: more than 5 at % to 13 at % or less; V: 3 at % or more to 9.5 at % or less; and Ti: 0 at % or more to 3.5 at % or less, with the remainder being Ni and unavoidable impurities, wherein the amount of V is not less than the amount of Nb; carrying out a solid solution treatment (homogenizing treatment); then carrying out a first heat treatment at a temperature at which the primary L12 phase and an Al phase coexist; and then cooling the alloy material to a temperature at which the primary L12 phase and a D022 phase and/or a D024 phase and/or a D0a phase coexist, or further subjecting the alloy material to a second heat treatment at this temperature, thereby converting the Al phase to an (L12 phase+D022 phase and/or D0a phase) eutectoid microstructure to form a multi-phase microstructure.
The phrase “carrying out a solid solution heat treatment (homogenizing heat treatment)” as used in the present embodiments means heating to and maintaining at the temperatures in the range indicated by Al in
In the present embodiments, the alloy material may be first subjected to a solid solution heat treatment (homogenization heat treatment). The homogenization heat treatment is typically carried out at a higher temperature than that of a first heat treatment which is performed subsequently. The homogenization heat treatment is preferably carried out at a temperature in the range of 1523 to 1623 K. Here, the first heat treatment and the homogenization heat treatment may be carried out together.
In the present embodiments, the alloy is subjected to the homogenization heat treatment, and then is subjected to the first heat treatment. The first heat treatment is carried out at a temperature at which both of the primary L12 phase and the Al phase coexist. The temperature at which the primary L12 phase and the Al phase coexist is specifically the temperature at which the alloy is in the Al+L12 state shown in
In the present embodiments, the phrase “the first heat treatment is carried out at a temperature at which both of the primary L12 phase and the Al phase coexist” means carrying out a heat treatment in the region described as Al+L12 in
Due to these states, from the results of the Examples below, it is assumed that the Al phases exist in between the cuboidal or rectangular primary L12 phases in the microstructure. This type of microstructure including the primary L12 phases and the intervening phases can be referred to as “upper multi-phase microstructure”.
The time for carrying out this first heat treatment is not particularly restricted. However, it is desirable to carry out the first heat treatment over a time period sufficient for the entire alloy to become a microstructure including the primary L12 phase and the Al phase. The time period for carrying out the first heat treatment is, for example, 5 to 20 hours.
The phrase “carrying out a second heat treatment in a region indicated by L12+D022 on the alloy material which is already subjected to the first heat treatment” means carrying out a heat treatment, for example, at a temperature not more than temperatures indicated by the symbols “” in
In the case in which the second heat treatment is carried out after the first heat treatment, cooling may be accomplished by natural cooling or forcible cooling such as water-quenching. The natural cooling may be carried out, for example, by taking out the alloy material from a heat-treatment furnace after the first heat treatment and then allowing the resulting alloy material to be put at room temperature, or by turning off a heater of the heat-treatment furnace after the first heat treatment and then allowing the resulting alloy material to be put in the heat-treatment furnace.
A temperature for the second heat treatment is, for example, about 1173 K to about 1281 K. A period for the second heat treatment is, for example, about 5 to 20 hours, for example. The Al phase may be decomposed into the L12 phase and the D022 phase by the cooling such as the simply water-quenching and the like without the second heat treatment. However, the decomposition can be more reliably achieved by the heat treatment at the relatively high temperature. After the second heat treatment, the resulting alloy material may be cooled to the room temperature by natural cooling or forcible cooling. Note that the word “to” expressing a range as used in the present specification includes the boundary values of the range unless otherwise described.
The reasons for limiting the various components of the Ni-based compound superalloy according to the present invention will now be explained below.
As is clear from the longitudinal phase diagram in
The amount of Nb may be in the range of 3 at % or more to 9.5 at % or less, and may be equal to, or less than the amount of V. To restate, the amount of V must be equal to or greater than the amount of Nb. This is because in the Ni-based compound superalloy of the present embodiments, a portion of V is substituted by Nb in order to improve the property of resistance to oxidation. Resistance to oxidation improves more as the amount of the V portion substituted with Nb increases. Note that the Ni-based compound superalloy of the present embodiments includes a smaller amount of V, includes Nb, and includes a larger amount of Al, as compared to the Ni-based compound superalloy which was researched by the present inventors and includes Al: 5 to 13 at %, V: 9.5 to 17.5 at %, Ti: 0 to 3.5 at %, and B: 1000 ppm (weight) or less, with the remainder being Ni, and has a dual multi-phase microstructure including a primary L12 phase and an (L12+D022 and/or D024 phase and/or D0a phase) eutectoid microstructure. These are the different features.
Co and Cr are elements that contribute to improving resistance to oxidation. Co is preferably added in the range of 0 at % or more to 15 at % or less, and Cr is preferably added in the range of 0 at % or more to 5 at % or less.
Co is an element which has complete solid solubility in Ni, so that Co is soluble in intermetallic compounds, Ni3Al, Ni3V, (Ni3Ti), and the like. In order to maintain the characteristics of a Ni-based alloy, the added amount is set to be up to 15 at %.
Cr is effective of improving resistance to oxidation. However, because the solid solubility of Cr in Ni3Al is low, there is a concern that unnecessary precipitates will be generated if Cr is added in a quantity of more than 5 at %. Accordingly, it is preferable to set the upper limit for addition of Cr to be 5 at %.
The bonding strength of V with oxygen is high, so that the surface of the alloy material readily oxidizes. Accordingly, by decreasing the amount of V, it is possible to improve resistance to oxidation. At the same time, V can be substituted with Nb which has the same valence number. Further, by increasing the amount of Al, it is possible to generate a fine oxidized film of alumina on the surface. By decreasing the amount of V, resistance to oxidation can be improved. However, if the amount of Nb exceeds the amount of V, it becomes difficult to obtain a multi-phase microstructure. Accordingly, it is necessary to increase the amount of V to be greater than the amount of Nb.
The amount of Ti is in the range of 0 at % or more to 3.5 at % or less, preferably in the range of 0.5 to 3.5 at % or less, more preferably in the range of 1 to 3.5 at %, and most preferably in the range of 2 to 3 at %. It is preferable that the Ni-based compound superalloy according to the present invention includes Ti; however, it is also acceptable not to include Ti.
The amount of Ni is preferably in the range of 73 to 77 at %, and more preferably in the range of 74 to 76 at %. This is because, in this range, the amount of Ni: the total amount of (Al, Ti, and V) approaches nearly 3:1, and therefore, a solid solution phase of Ni, Al, Ti, or V is essentially non-existent.
The amount of B is in the range of 0 ppm (weight) or more to 1000 ppm (weight) or less, preferably in the range of 1 to 1000 ppm (weight), more preferably in the range of 1 to 500 ppm (weight), and even more preferably in the range of 5 to 100 ppm (weight). It is preferable that the Ni-based compound superalloy according to the present invention includes B; however it is also acceptable that B is not included.
In addition to the various elements of the above composition, it is also acceptable to include Mo in the amount of 1 to 2 at %. Mo is an element that has the effect of improving high-temperature strength, and has complete solid solubility in V. The amount of Mo preferably satisfies V>Mo+Nb. Further, the method for strengthening the crystal grain boundary may be considered as an approach for improving ductility. For this purpose, trace quantities of elements such as C, Zr, and Hf may be added up to a maximum of 0.2 at %. It is also acceptable to include any one of elements C, Zr and Hf in a trace amount of 0.2 at % or less.
The Ni-based compound superalloy according to the present invention has a multi-phase microstructure which includes an upper multi-phase microstructure and a lower multi-phase microstructure as described above, and it is most preferable that this Ni-based compound superalloy includes a dual multi-phase microstructure including these multi-phase microstructures.
It will be demonstrated experimentally in the Examples which will follow below that the Ni-based compound superalloy according to the present invention has superior mechanical properties at high temperatures and superior resistance to oxidation. It is thought that the reason for these superior properties is because the Ni-based compound superalloy according to the present invention has the multi-phase microstructure that includes the upper multi-phase microstructure and the lower multi-phase microstructure and, the having of the aforementioned dual multi-phase microstructure of the upper multi-phase microstructure and the lower multi-phase microstructure, which is the more preferable feature, is thought to be a contributing factor to attain more superior characteristics.
Note that it is desirable that the multi-phase microstructure or the dual multi-phase microstructure forms the entire Ni-based compound superalloy according to the present invention; however, it is not necessary that the entire Ni-based compound superalloy has this microstructure. Rather, it is acceptable that at least a portion, or more preferably 50% or more, of the entire microstructure be composed of the multi-phase microstructure.
The crystal structures of the intermetallic compounds employed in the Ni-based compound superalloy according to the present invention are simple as compared to the other three constituent phases (D022 phase, D024 phase, and D0a phase). As a result, it is thought that the Ni-based compound superalloy according to the present invention includes a primary phase L12 in which dislocations are comparatively activated, and a certain degree of ductility occurs over an entire range of temperatures including a room temperature. Accordingly, this facilitates handling of the Ni-based compound superalloy.
The Ni-based compound superalloy according to the present invention has superior mechanical properties at high temperatures. Accordingly, it can be used as a heat resistant structural material. Further, among the component elements, a portion of V is substituted by Nb; thereby, improving the resistance to oxidation. Further, by adding Co and Cr in suitable quantities, resistance to oxidation is also increased.
In addition, in the case in which a composition is provided in which a portion of V is substituted by Nb, it is disadventageous to some extent from the perspective of reducing weight; however, there is a weight reduction on the order of about 0.5 g/cm3 as compared to the typical Ni-based superalloy.
The above-described Ni-based compound superalloy can be effectively utilized in a temperature range that is slightly lower than 1523 K (1250° C.), for example, at high temperatures up to 1273 K to 1373 K (1000 to 1100° C.), and is suitable for low-pressure turbine blades of a turbo charger or an engine. In the case in which the high-temperature strength is high in this temperature range, the effect of achieving the same resistance to pressure at a lower weight can be realized. Thus, this is beneficial from the perspective of engine efficiency and fuel costs.
Examples of the alloy material employed to manufacture the Ni-based compound superalloy according to the present invention include a casting material, a forging material, a single crystal material, and the like. The casting material can be formed by melting (arc melting, high frequency melting, and the like) a pre-weighed raw metal, then pouring it into a casting mould, and permitting it to solidify.
The casting material is a polycrystal typically having crystal grains on the order of several hundred microns to several millimeters, and has a disadvantage of readily fracturing at boundaries between the crystal grains (crystal grain boundaries), and a disadvantage of having casting defects such as shrinkage cavities and the like. The forging material improves on these disadvantages. The forging material is formed by subjecting a casting material to a hot forging and a recrystallization annealing. These hot forging and recrystallization annealing are typically carried out at temperatures which are higher than the temperature of the first heat treatment.
The temperatures at which the hot forging and the recrystallization annealing are carried out may be the same or different. It is preferable to carry out the hot forging at around 1523 to 1623 K, and the recrystallization annealing at around 1423 to 1573 K. Prior to the first heat treatment, the alloy material may be subjected to a homogenization heat treatment. The homogenization heat treatment is typically carried out at a temperature which is higher than that of the first heat treatment. The homogenization heat treatment is preferably carried out in the range of around 1523 to 1623 K. The first heat treatment may be carried out together with the homogenization heat treatment. In the case of the forging material, the hot forging and the recrystallization annealing may be carried out together with the homogenization heat treatment. The time period for carrying out the homogenization heat treatment is not restricted; however, for example, it is on the order of 24 to 96 hours. In the case in which the alloy material is a polycrystal material (casting material, forging material, or the like), it is preferable to include B in the alloy material. The reason for this is because the crystal grain boundaries are strengthened as a result.
If a compression testing and a tensile testing are carried out to a Ni-based compound superalloy having a multi-phase microstructure which is formed by heat-treating a casting material, a forging material, or a single crystal material, it can be confirmed that the Ni-based compound superalloy has superior mechanical properties on any of these testing.
Various specific examples of the Ni-based compound superalloy according to the present invention will now be explained.
In the following examples, Ni-based compound superalloys having multi-phase microstructures were manufactured by carrying out heat treatments, and the mechanical properties thereof were investigated.
In the following examples, the heat treatment at 1373 K corresponds to the first heat treatment (primary precipitation heat treatment) at a temperature at which the primary L12 phase and the Al phase coexist (first state), and the water-quenching carried out after performing the heat treatment at 1373 K corresponds to cooling to a temperature at which the L12 phase and the D022 phase coexist. The heat treatment at 1173 K or 1273 K carried out after performing the heat treatment at 1373 K corresponds to the second heat treatment (secondary precipitation heat treatment) at a temperature at which the L12 phase and the D022 phase coexist.
Prior to producing test materials employing the composition system according to the present invention, Ni, Al, Ti, and V raw metals (each having 99.9 wt % purity) in the proportions indicated in Nos. 1 to 20 in Table 1 were melted in an arc melting furnace for obtaining casting materials for prescribing the composition limits of alloys resembling the present invention. With regard to the atmosphere inside the arc melting furnace, the melting chamber was evacuated and then the atmosphere was replaced with an inert gas (argon gas). A non-consumable tungsten electrode was employed for the electrode, and a water-cooled copper hearth was employed for the casting mold. In the case of adding other elements in addition to the above, it is acceptable to use raw metals in which elements such as Co, Cr, Mo, B, C, Hf, and the like are added in accordance with the required alloy composition, or to add ingots of these elements separately during melting.
In the following explanation, the aforementioned casting materials will be referred to as “samples”.
For actually manufacturing the Ni-based compound superalloy according to the present invention, Ni, Al, Ti, and V raw metals were employed to obtain samples so as to produce Test Materials Nos. 1 to 20 having the various compositions shown in Table 1, in order to obtain a phase diagram of the basic composition system of the Ni-based compound superalloy according to the present invention.
From the longitudinal phase diagram in
From Table 1 and
Next, the Ni3Al—Ni3Ti—Ni3V pseudo-ternary phase diagram at 1273 K was determined in accordance with the phase diagram shown in
Test Materials Nos. 1 to 20 were vacuum-sealed in quartz tubes, and each was subjected to a heat treatment at 1273 K for 7 days, and then was subjected to a water-quenching. Next, in order to form the phase diagram at 1273 K, an observation of microstructure and an analysis of each constituent phase were performed for each of Test Materials Nos. 1 to 20. The observation of microstructure was carried out using OM (Optical Microscope), SEM, and TEM. The analysis of the various constituent phases was carried out using SEM-EPMA (Scanning Electron Microscope-Electron Probe MicroAnalyzer). The results of this observation and analysis are shown in Table 1. The Ni3Al—Ni3Ti—Ni3V pseudo-ternary phase diagram at 1273 K obtained from this observation and an analysis is shown in
The composition range surrounded by points A, B, C, D, and E shown in
The present invention is realized by reducing the amount of V and substituting a portion of V with Nb within the above composition range. As a result, by providing a composition within the range surrounded by lines that connect point A (Al: 14.0 at %, Ti: 0 at %, (V+Nb): 11.0 at %, Ni: 75 at %), point B (Al: 12.5 at %, Ti: 2.8 at %, (V+Nb): 9.8 at %, Ni: 75 at %), point C (Al: 8.0 at %, Ti: 3.8 at %, (V+Nb): 13.3 at %, Ni: 75 at %), point D (Al: 2.3 at %, Ti: 2.0 at %, (V+Nb): 20.8 at %, Ni: 75 at %), and point E (Al: 2.0 at %, Ti: 0 at %, (V+Nb): 23.0 at %, Ni: 75 at %), in the Ni3Al—Ni3Ti—Ni3V pseudo-ternary phase diagram shown in
Test materials having the compositions shown in Table 2 below were prepared, and then the properties thereof were evaluated in order to investigate the composition and the microstructure of the Ni-based compound superalloy having the composition system according to the present invention, based on the Ni3Al—Ni3Ti—Ni3V pseudo-ternary phase diagram shown in
Each sample having the compositions shown in Table 2 was melted and subjected to a heat treatment at 1573 K (1300° C.) for 10 hours in a vacuum furnace. This treatment corresponds to a homogenizing treatment. Next, argon gas was introduced into the furnace by means of a gas fan cooling, and stirring and cooling was performed. Next, gas fan cooling was carried out at 1373 K (1100° C.) for 10 hours (first heat treatment), and then gas fan cooling was carried out at 1273 K (1000° C.) for 10 hours (second heat treatment). Each test material was thus obtained and supplied for the following compression tests.
Test Materials Nos. 21, 22 and 28 shown in Table 2 were employed. The compression test was performed using square test pieces having dimensions of 2×2×5 mm3 under conditions where the temperature is in a range of the room temperature to 1273 K, the atmosphere is vacuum, and the strain rate is 3.3×10−4 s−1. These results are shown in
From the results of the compression tests shown in
Also, in
In
From the results shown in
Further, it was clear that all of the test materials had superior oxidation resistance as compared to a test material of the Ni3Al—Ni3Ti—Ni3V system alloy (test material containing Al: 7.5% in
In the photo of Test Material No. 21, the contrast was poor so that it was difficult to discriminate; however, it was possible to confirm the presence of the Ni3Al (L12) phase in almost the entirely of the test material. From the partially enlarged view (5000 times) of the photo of the metallographic structure of this test material, it was clear that a dual multi-phase microstructure including a primary L12 phase and an (L12+D022) eutectoid microstructure was formed.
In the photos of Test Materials Nos. 22 and 23, the Ni3Al (L12) phase is clearly confirmed; however, it is clear that the amount of the Ni3Al(L12) phase is reduced. When the amount of the Ni3Al (L12) crystal grains decreases as in the photo, formation of the multi-phase microstructure tends to become difficult. (Test Material No. 21 includes V: 7 at %, Nb 3 at % as shown in Table 2; Test Material No. 22 includes V, Nb: 5 at %; and Test Material No. 23 includes V: 0 at %, Nb: 10 at %.)
Among these metallographic structures, those that include a multi-phase microstructure or include a dual multi-phase microstructure do not readily undergo large changes in microstructure even at high temperatures. Due to this stability, a large high-temperature strength is attained. Further, it is important to form a microstructure in which these multi-phase microstructures are formed as finely and as coherently as possible for the purpose of enabling a microstructure which has superior mechanical properties at even higher temperatures.
The fine granular portion in the photo of the metallographic structure shown in
From the above photos of microstructures, it is clear that test materials to which the combined addition of Cr and Co as well as the combined addition of V and Nb is employed, such as Test Material No. 28, also have a multi-phase microstructure.
Note that while a Ni3Ti phase is observed in the lower left side of the photos of the metallographic structures in
The specific gravity of Test Material No. 21 was 7.90. The specific gravity of Test Material No. 22 was 7.95. The specific gravity of Test Material No. 23 was 8.07. The specific gravity of Test Material No. 24 was 7.90. The specific gravity of Test Material No. 25 was 7.87. The specific gravity of Test Material No. 26 was 7.88. The specific gravity of Test Material No. 27 was 7.8. The specific gravity of Test Material No. 28 was 7.86. From these, it is clear that it is possible to achieve a reduction in weight as compared to the typical Ni-based superalloys such as MarM247 (registered trademark): 8.54 g/cm3 and CMSX-4 (registered trademark): 8.70 g/cm3.
Next, based on the Ni3Al—Ni3Ti—Ni3V pseudo-ternary phase diagram shown in
Test materials having the compositions shown in Table 3 were produced in the same manner as the test materials shown in Table 2, and the oxidation resistance test was performed for each test material at a testing temperature of 1000° C. These results are shown in
From the results shown in
Various samples having the compositions shown in Table 4 were melted and subjected to a heat treatment at 1563 K (1290° C.) for 10 hours in a vacuum furnace. This treatment corresponds to a homogenizing treatment. Next, argon gas was introduced into the furnace by means of a gas fan cooling, and stirring and cooling was carried out. Next, a heat treatment was carried out at 1373K (1100° C.) for 10 hours, and then gas fan cooling was carried out (first heat treatment). Thereafter, a heat treatment was carried out at 1273 K (1000° C.) for 10 hours, and then gas fan cooling was carried out (second heat treatment). Each test material was thus obtained and supplied for the following tests.
For the test materials shown in Table 4, the specific gravity of Test Material No. 41 was 7.94, and the specific gravity of Test Material No. 65 was 8.01. In contrast, the specific gravity of Test Material No. 10 in Table 1 was 8.00. From these, it is clear that it is possible to achieve a reduction in weight for Test Materials Nos. 41 and 65 as compared to the above-described typical Ni-based superalloys such as MarM247 (registered trademark): specific gravity is 8.54 and CMSX-4 (registered trademark): specific gravity is 8.70.
From the results of the oxidation tests shown in
The same oxidation tests were conducted for Test Materials Nos. 51 to 58 and Test Materials Nos. 63 to 67 shown in Table 4, and the results of Test Materials Nos. 51 to 58 are shown in
From the results of the oxidation tests shown in
Next, the results of tensile tests carried out on Test Materials Nos. 28, 41, and 65 shown in Tables 2 and 4 are shown in
From among the test materials shown in Table 4, photos of metallographic structures of Test Materials Nos. 41, 47, 48, 52, 57 and 65 are shown in
From these photos of the metallographic structures, it is clear that the fine granular portion in the photo of the metallographic structure is the L12-D024-D0a microstructure and occupies the majority (entirety) of the microstructure in the photo for each of Test Materials Nos. 47, 48, 52, 57 and 65.
As is clear from comparing
The Ni-based compound superalloy according to the present invention can be employed as a structural material where high-temperature heat resistance is required, such as for an engine. The Ni-based superalloy according to the present invention has a slightly lower specific gravity than those of conventional Ni-based superalloys, and has superior in oxidation resistance and excellent tensile strength at high temperatures. As a result, an improvement in engine efficiency can be attained in the engine in which the Ni-based compound superalloy according to the present invention is employed.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-261569 | Sep 2006 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2007/068720 | 9/26/2007 | WO | 00 | 4/13/2009 |
