High temperature aging heat treatment method for nickel-based single crystal high temperature alloy and preparation method of nickel-based single crystal high temperature alloy

Abstract

The present invention provides a high-temperature aging heat treatment method for a nickel-based single crystal high-temperature alloy, comprising the following steps: A) determining the highest temperature t0 that the alloy can withstand during use; B) placing the alloy after solution heat treatment at a temperature t1 not lower than t0 for heat preservation; C) placing the alloy obtained in step B) at a temperature slightly lower than t2 for heat preservation; D) rapidly cooling the alloy obtained in step C). The present application also provides a method for preparing a nickel-based single crystal high-temperature alloy. The aging heat treatment method for a nickel-based single crystal high-temperature alloy provided by the present invention is based on the highest temperature that can be borne during use, and the alloy is placed at t1 for a primary high-temperature aging heat treatment, which can reduce the stress aging of the strengthening phase γ′ during use, so that the alloy has better stability; and then placed at t2 for a secondary high-temperature aging heat treatment, which can further precipitate the alloy strengthening phase γ′ phase, better exert its strengthening effect, and thus make the alloy have better high-temperature performance.

Description

Technical Field

[0001] The present invention relates to the technical field of nickel-based single crystal high-temperature alloys, and in particular to a high-temperature aging heat treatment method for a nickel-based single crystal high-temperature alloy and a preparation method for the nickel-based single crystal high-temperature alloy. Background Art

[0002] Nickel-based single crystal superalloy (hereinafter referred to as "single crystal superalloy") is a cast superalloy with a single columnar crystal structure, which contains multiple alloy elements such as Ni, Cr, Co, W, Mo, Al, etc. and is prepared by directional solidification and crystal selection (seed crystal) technology. Because the adverse effects of grain boundaries on the high temperature properties of alloys are eliminated, single crystal superalloys have excellent high temperature comprehensive properties and are the preferred material for advanced aircraft engine turbine blades.

[0003] The microstructure of single crystal high temperature alloy plays a decisive role in the high temperature mechanical properties of the alloy, and the preparation processes that affect the alloy microstructure mainly include directional solidification process and heat treatment process. During the directional solidification process, the alloy solidifies into dendrites with consistent orientation in the liquid phase. However, due to element segregation, the γ′ strengthening phase morphology between the dendrite trunk and the dendrites is quite different, such as Figure 1 Therefore, it is necessary to adjust the morphology of the alloy strengthening phase γ′ through heat treatment to achieve a better strengthening effect and enable the alloy to obtain better high-temperature mechanical properties.

[0004] The heat treatment of single crystal high temperature alloys is divided into solution heat treatment and aging heat treatment. Among them, solution heat treatment can make the alloy elements fully diffuse and achieve composition homogenization; at the same time, the strengthening phase γ′ between the dendrite stem and the dendrites becomes fine and uniform, and is evenly distributed in the dendrite stem and the dendrites, achieving organizational homogenization, such as Figure 2 In the subsequent aging heat treatment, the strengthening phase γ′ grows into a cubic shape within a certain size range, thereby obtaining a better strengthening effect, as shown in Figure 3 shown.

[0005] The excellent high-temperature performance of single-crystal high-temperature alloys is largely derived from the precipitation phase strengthening effect brought about by the γ' strengthening phase coherently precipitated from the γ matrix. Aging heat treatment is an important way to adjust the volume percentage and morphology of the γ' phase. Therefore, aging heat treatment is particularly important for the high-temperature performance of the alloy.

[0006] In order to meet the development needs of advanced aero-engines, the first to fifth generations of single crystal superalloys have been developed successively at home and abroad, and the high-temperature aging heat treatment temperature used is mostly not higher than 1120℃. The first and second generation single crystal superalloys have a temperature bearing capacity of no higher than 1100℃. After the alloy is aged at no higher than 1120℃, it can be used at no higher than 1100℃ to ensure the structural stability of the strengthening phase; however, the third generation and above single crystal superalloys have a temperature bearing capacity of no less than 1120℃. At this time, the high-temperature aging heat treatment temperature of 1120℃ is still used, which will cause the use temperature to be higher than the aging heat treatment temperature, resulting in high-temperature stress aging of the alloy during service, affecting the structural stability of the strengthening phase and the high-temperature mechanical properties of the alloy. To solve the above problems, a small number of third generation and above single crystal superalloys have proposed aging heat treatment temperatures higher than 1120℃, but they are mainly for alloys with specific compositions or grades. At present, there is no aging heat treatment system design method based on the maximum use temperature at home and abroad. Summary of the invention

[0007] The technical problem solved by the present invention is to provide a high-temperature aging heat treatment method for a nickel-based single crystal high-temperature alloy, so that the nickel-based single crystal high-temperature alloy obtains excellent high-temperature performance.

[0008] In view of this, the present application provides a high temperature aging heat treatment method for a nickel-based single crystal high temperature alloy, comprising the following steps:

[0009] A) Determine the maximum temperature t0 that the nickel-based single crystal high-temperature alloy can withstand during use;

[0010] B) keeping the nickel-based single crystal high-temperature alloy after solution heat treatment at t1;

[0011] C) keeping the nickel-based single crystal high-temperature alloy obtained in step B) at t2;

[0012] D) rapidly cooling the nickel-based single crystal high-temperature alloy obtained in step C);

[0013] Among them, t0≤t1≤t0+30℃, t0-40℃≤t2≤t0+10℃, and t1>t2.

[0014] Preferably, t1>t2>1000℃.

[0015] Preferably, in step B), the insulation time is 15 minutes to 5 hours.

[0016] Preferably, in step C), the insulation time is 2h to 6h.

[0017] Preferably, 10°C≤t1-t2≤60°C.

[0018] Preferably, the cooling rate of the rapid cooling is ≥200°C / min, and the rapid cooling is cooling from t2 to below 500°C.

[0019] Preferably, the t0 satisfies 1050-1180°C.

[0020] Preferably, in step B), the insulation time is 15 minutes to 2 hours; in step C), the insulation time is 3 to 4 hours.

[0021] Preferably, the γ / γ′ distribution in the nickel-based single crystal high-temperature alloy after rapid cooling is uniform and regular in size, and the strengthening phase γ′ is cubic with a size of not less than 250 nm and not more than 500 nm.

[0022] The present application also provides a method for preparing a nickel-based single crystal high-temperature alloy, comprising batching, smelting, directional solidification, solution heat treatment, high-temperature aging heat treatment, and medium / low-temperature aging heat treatment in sequence, wherein the high-temperature aging heat treatment is the high-temperature aging heat treatment method described in the above scheme.

[0023] The present application provides a high-temperature aging heat treatment method for a nickel-based single crystal high-temperature alloy, which first determines the maximum temperature that the nickel-based single crystal high-temperature alloy can withstand during use, and designs a two-stage aging temperature for the high-temperature aging heat treatment according to the maximum use temperature, thereby enabling the γ / γ′ microstructure of the nickel-based single crystal high-temperature alloy to be uniformly distributed and regular in size after the aging heat treatment. By undergoing an aging heat treatment at a temperature higher than the use temperature, stress aging of the strengthening phase γ′ during use can be avoided, so that the strengthening phase γ′ has better stability during service, thereby better exerting its strengthening effect, and further enabling the alloy to have more excellent high-temperature performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A photo of the cast structure of a nickel-based single crystal high-temperature alloy in the background technology of the present invention;

[0025] Figure 2 A photograph of the γ / γ′ structure of a nickel-based single crystal high-temperature alloy after solution heat treatment in the background technology of the present invention;

[0026] Figure 3 A γ / γ′ structure photograph of a nickel-based single crystal high-temperature alloy after aging heat treatment in the background technology of the present invention;

[0027] Figure 4 This is a photo of the γ / γ′ structure of the nickel-based single crystal high-temperature alloy after aging heat treatment according to Example 1 of the present invention;

[0028] Figure 5 This is a photo of the γ / γ′ structure of the nickel-based single crystal high-temperature alloy after aging heat treatment according to Example 2 of the present invention;

[0029] Figure 6 This is a photo of the γ / γ′ structure of the nickel-based single crystal high-temperature alloy after aging heat treatment according to Example 3 of the present invention;

[0030] Figure 7 This is a photo of the γ / γ′ structure of the nickel-based single crystal high-temperature alloy after aging heat treatment in Comparative Example 1 of the present invention;

[0031] Figure 8 This is a photograph of the γ / γ′ structure of the nickel-based single crystal high-temperature alloy after aging heat treatment in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0032] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0033] In view of the demand for high-temperature performance of nickel-based single-crystal high-temperature alloys in the prior art, at the same time, for different nickel-based single-crystal high-temperature alloys, especially high-generation nickel-based single-crystal high-temperature alloys with high content of high-melting-point alloying elements, slight changes in process parameters will greatly affect the alloy performance; at the same time, alloys with similar compositions have different organizational evolution laws under different service conditions, resulting in differences in alloy performance. Therefore, the organization of nickel-based single-crystal high-temperature alloys is affected by many conditions, and it is not possible to infer similar performance and predictable effects by similar compositions or similar preparation methods. The present application provides a high-temperature aging heat treatment method for nickel-based single-crystal high-temperature alloys in a pioneering manner. According to the highest temperature that the nickel-based single-crystal high-temperature alloys are subjected to during use, a two-stage specific treatment system for high-temperature aging heat treatment is designed, so that the γ / γ′ organizational size and morphology of the nickel-based single-crystal high-temperature alloys are better, and ultimately the high-temperature performance of the nickel-based single-crystal high-temperature alloys can be guaranteed. Specifically, the present application provides a high-temperature aging heat treatment method for nickel-based single-crystal high-temperature alloys, comprising the following steps:

[0034] A) Determine the maximum temperature t0 that the nickel-based single crystal high-temperature alloy can withstand during use;

[0035] B) keeping the nickel-based single crystal high-temperature alloy after solution heat treatment at t1;

[0036] C) keeping the nickel-based single crystal high-temperature alloy obtained in step B) at t2;

[0037] D) rapidly cooling the nickel-based single crystal high-temperature alloy obtained in step C);

[0038] Among them, t0≤t1≤t0+30℃, t0-40℃≤t2≤t0+10℃, and t1>t2.

[0039] In the high temperature aging heat treatment method of the nickel-based single crystal high temperature alloy provided in the present application, the present application first determines the maximum temperature t0 that the nickel-based single crystal high temperature alloy withstands during use. Depending on the nickel-based single crystal high temperature alloy product, the maximum temperature t0 is specifically 1000-1200°C, more specifically 1050-1180°C.

[0040] After the solution heat treatment, the present application first keeps the nickel-based single crystal high-temperature alloy after the solution heat treatment at t1. The value range of t1 is t0≤t1≤t0+30℃, more specifically, the value range of t1 is t0≤t1≤t0+10℃ or t0≤t1≤t0+20℃; the insulation time is 15min~5h, specifically, the insulation time is 15min~3h; more specifically, the insulation time is 15min~2h.

[0041] The present application then heats the nickel-based single crystal high-temperature alloy obtained above at t2; the value range of t2 is t0-40℃≤t2≤t0+10℃, more specifically, the value range of t2 is t0-30≤t2≤t0+10℃, t0-20≤t2≤t0+10℃, t0-10≤t2≤t0+10℃, t0-40℃≤t2≤t0, t0-30℃≤t2≤t0, t0-20℃≤t2≤t0 or t0-10℃≤t2≤t0; the heat preservation time is 2h~6h, specifically, the heat preservation time is 3h~4h. Further, 10℃≤t1-t2≤60℃, specifically, 10℃≤t1-t2≤40℃.

[0042] Finally, the present application rapidly cools the nickel-based single crystal high-temperature alloy obtained above. In the present application, the cooling rate of the rapid cooling is ≥200°C / min, and the rapid cooling is cooling from t2 to below 500°C.

[0043] The present application also provides a method for preparing a nickel-based single crystal high-temperature alloy, comprising batching, smelting, directional solidification, solution heat treatment, high-temperature aging heat treatment, and medium / low-temperature aging heat treatment in sequence, wherein the high-temperature aging heat treatment is the high-temperature aging heat treatment method described in the above scheme.

[0044] The aging heat treatment of single crystal high temperature alloys is usually divided into high temperature aging heat treatment and medium / low temperature aging heat treatment; among them, the adjustment of γ′ size and morphology is mainly completed during the high temperature aging heat treatment process, so the high temperature aging heat treatment process plays a vital role in the high temperature strength of nickel-based single crystal high temperature alloys. The high temperature aging heat treatment method of nickel-based single crystal high temperature alloy provided by the present invention designs a high temperature aging heat treatment system according to the use temperature of single crystal high temperature alloy castings, so that the γ′ phase can better play a strengthening role during the service process, so that the alloy has better high temperature performance.

[0045] In order to further understand the present invention, the high temperature aging treatment method of the nickel-based single crystal high temperature alloy provided by the present invention is described in detail below in combination with the embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0046] Example 1

[0047] 1) Design a high temperature aging heat treatment system for a nickel-based single crystal high temperature alloy, which is used for turbine blades of aircraft engines. Its composition is shown in Table 1;

[0048] Table 1 Composition data of nickel-based single crystal high temperature alloy provided in this embodiment (mass percentage wt%)

[0049] Al Ta Ru Co W Mo Cr Re Nb Hf Ni 5.5 7.5 6.5 6.2 7.0 2.1 2.2 6.0 0.5 0.1 Bal.

[0050] 2) The alloy high temperature aging heat treatment system is as follows:

[0051] A) According to the use environment of the above nickel-based single crystal high-temperature alloy, the highest temperature t0 of the alloy in service is 1150°C;

[0052] B) the alloy which has undergone the solution heat treatment is placed at t1 = 1170°C for 15 min;

[0053] C) placing the alloy obtained in step B) at t2 = 1140° C. for 4 hours;

[0054] D) rapidly cooling the alloy obtained in step C) to below 500° C. at a cooling rate of not less than 260° C. / min.

[0055] The alloy structure of the nickel-based single crystal high-temperature alloy obtained by the above method is as follows: Figure 4 As shown by Figure 4 It can be seen that the γ / γ′ structure in the alloy is evenly distributed and regular in size, and the strengthening phase γ′ is cubic with a size of about 416 nm.

[0056] The alloy after high temperature aging treatment was further subjected to low temperature aging heat treatment at 870°C / 32h. The alloy was tested for its endurance life of 112h at 1150°C / 137MPa.

[0057] Example 2

[0058] A nickel-based single crystal high temperature alloy, the alloy composition is shown in Table 2, the alloy is used for turbine blades for aircraft engines, and the maximum temperature is 1120°C (here refers to the actual temperature of the blade material when the blade is in service, not the temperature before the turbine);

[0059] Table 1 Composition data of nickel-based single crystal high temperature alloy provided in this embodiment (mass percentage wt%)

[0060] Al Ta Co W Mo Cr Re Nb Hf Ni 5.6 7.2 8.7 6.5 1.6 1.8 7.0 0.5 0.1 Bal.

[0061] According to the process of Example 1, a high-temperature aging treatment of a nickel-based single crystal high-temperature alloy is performed, and a high-temperature aging heat treatment system of the alloy is designed according to the maximum temperature: 1130°C / 15min+1120°C / 4h;

[0062] The nickel-based single crystal high-temperature alloy of this embodiment has a microstructure after high-temperature aging heat treatment. Figure 5 As shown in the figure, it can be seen that the γ / γ′ structure in the alloy is evenly distributed and regular in size, and the strengthening phase γ′ is about 454nm in size.

[0063] The alloy after high temperature aging treatment was further subjected to low temperature aging heat treatment at 870°C / 32h. The alloy was tested to have a durability of 122h at 1120°C / 137MPa.

[0064] Example 3

[0065] A nickel-based single crystal high temperature alloy, the alloy composition is shown in Table 3, the alloy is used for turbine blades for aircraft engines, and the maximum temperature is 1160°C (here refers to the actual temperature of the blade material when the blade is in service, not the temperature before the turbine);

[0066] Table 2 Composition data of nickel-based single crystal high temperature alloy provided in this embodiment (mass percentage wt%)

[0067] Al Ta Ru Co W Mo Cr Re Nb Hf Ni 5.4 7.2 6.2 8.5 6.7 1.7 1.8 7.2 0.4 0.1 Bal.

[0068] The high-temperature aging treatment of the nickel-based single crystal high-temperature alloy was carried out according to the process of Example 1, and the high-temperature aging heat treatment system of the alloy was designed according to the maximum temperature: 1180°C / 15min+1140°C / 4h.

[0069] The nickel-based single crystal high-temperature alloy of this embodiment has a microstructure after high-temperature aging heat treatment. Figure 6 As shown in the figure, it can be seen that the γ / γ′ structure in the alloy is evenly distributed and regular in size, and the strengthening phase γ′ is about 346nm in size.

[0070] The alloy after high temperature aging treatment was further subjected to low temperature aging heat treatment at 870°C / 32h. The alloy was tested for its endurance life of 112h at 1160°C / 137MPa.

[0071] Comparative Example 1

[0072] A nickel-based single crystal high temperature alloy, the alloy composition is shown in Table 4, the alloy is used for turbine blades for aircraft engines, and the maximum temperature is 1160°C (here refers to the actual temperature of the blade material when the blade is in service, not the temperature before the turbine);

[0073] Table 4 Composition data of nickel-based single crystal high temperature alloy provided in this embodiment (mass percentage wt%)

[0074] Al Ta Ru Co W Mo Cr Re Nb Hf Ni 5.4 7.2 6.2 8.5 6.7 1.7 1.8 7.2 0.4 0.1 Bal.

[0075] The high-temperature aging treatment of the nickel-based single crystal high-temperature alloy was carried out according to the process of Example 3. The high-temperature aging heat treatment system of the alloy was designed according to the maximum temperature: 1180°C / 15min; then, the alloy after the high-temperature aging treatment was further subjected to a low-temperature aging heat treatment of 870°C / 32h.

[0076] The alloy structure of the nickel-based single crystal high-temperature alloy in this comparative example after aging heat treatment is as follows Figure 7 As shown in the figure, it can be seen that the γ / γ′ morphology of the dendrite trunk (left picture) and the dendrites (right picture) in the alloy is obviously different, indicating that the alloy has serious dendritic segregation.

[0077] The alloy after high temperature aging treatment has a durability life of 12h at 1160℃ / 137MPa.

[0078] Comparative Example 2

[0079] A nickel-based single crystal high temperature alloy, the alloy composition is shown in Table 4, the alloy is used for turbine blades for aircraft engines, and the maximum temperature is 1160°C (here refers to the actual temperature of the blade material when the blade is in service, not the temperature before the turbine);

[0080] Table 4 Composition data of nickel-based single crystal high temperature alloy provided in this embodiment (mass percentage wt%)

[0081] Al Ta Ru Co W Mo Cr Re Nb Hf Ni 5.4 7.2 6.2 8.5 6.7 1.7 1.8 7.2 0.4 0.1 Bal.

[0082] The high-temperature aging treatment of the nickel-based single crystal high-temperature alloy was carried out according to the process of Example 1. The high-temperature aging heat treatment system of the alloy was designed according to the maximum temperature: 1120°C / 6min; then, the alloy after the high-temperature aging treatment was further subjected to a low-temperature aging heat treatment of 870°C / 32h.

[0083] The alloy structure of the nickel-based single crystal high-temperature alloy in this comparative example after aging heat treatment is as follows Figure 8 As shown,

[0084] As can be seen from the figure, the difference in γ / γ′ morphology between the dendrite trunk (left figure) and the dendrites (right figure) in the alloy is smaller than that in comparative example 1, but there are still obvious differences, and the organizational uniformity is not ideal.

[0085] The alloy after high temperature aging treatment has a durability life of 45h at 1160℃ / 137MPa.

[0086] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0087] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high temperature aging heat treatment method for a nickel-based single crystal high temperature alloy, comprising the following steps: A) Determine the maximum temperature t0 that the nickel-based single crystal high-temperature alloy can withstand during use; B) keeping the nickel-based single crystal high-temperature alloy after the solution heat treatment at t1; the holding time is 15 minutes to 5 hours; C) keeping the nickel-based single crystal high-temperature alloy obtained in step B) at t2; the keeping time is 2h to 6h; D) rapidly cooling the nickel-based single crystal high-temperature alloy obtained in step C); Wherein, the t0 satisfies 1050-1180°C, t0≤t1≤t0+30°C, t0-40°C≤t2≤t0+10°C, and t1>t2.

2. The high temperature aging heat treatment method according to claim 1, characterized in that: t1>t2>1000℃.

3. The high temperature aging heat treatment method according to claim 1, characterized in that: 10℃≤t1-t2≤60℃.

4. The high temperature aging heat treatment method according to claim 1, characterized in that: The cooling rate of the rapid cooling is ≥200°C / min, and the rapid cooling is cooling from t2 to below 500°C.

5. The high temperature aging heat treatment method according to claim 1, characterized in that: In step B), the insulation time is 15 minutes to 2 hours; in step C), the insulation time is 3 to 4 hours.

6. The high temperature aging heat treatment method according to any one of claims 1 to 5, characterized in that: After rapid cooling, the γ / γ′ in the nickel-based single crystal high-temperature alloy is evenly distributed and regular in size, and the strengthening phase γ′ is cubic with a size of not less than 250nm and not more than 500nm.

7. A method for preparing a nickel-based single crystal high-temperature alloy, comprising batching, smelting, directional solidification, solution heat treatment, high-temperature aging heat treatment, and medium / low-temperature aging heat treatment in sequence, characterized in that: The high temperature aging heat treatment is the high temperature aging heat treatment method according to any one of claims 1 to 6.

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