A low-cobalt, medium-rhenium improved second-generation nickel-based single crystal superalloy, a preparation method and application thereof

Abstract

This invention provides a low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal superalloy, its preparation method, and its applications. By mass fraction, it comprises the following elements: Cr 1.5~3.0%, Co 2.0~4.0%, W 6.0~8.0%, Mo 0.5~2.0%, Ta 6.5~8.5%, Re 3.5~4.8%, Al 5.2~6.5%, Ti 0~0.4%, Hf 0~0.15%, with the balance being Ni. Under the combined effect of the above-mentioned components, the high-temperature creep life of this alloy is significantly improved, especially its creep performance under high-temperature and low-stress conditions above 950℃. Furthermore, compared to third-generation nickel-based single-crystal superalloys, this alloy exhibits excellent long-term high-temperature microstructure stability without the precipitation of long needle-like topological harmful phases during long-term thermal exposure at 1100℃ / 1000 hours.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature structural materials technology, and particularly relates to a low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal high-temperature alloy, its preparation method, and its application. Background Technology

[0002] Nickel-based single-crystal superalloy blades for high-pressure turbines and gas turbines for aero-engines are subjected to extremely harsh thermal loads and oxidation / corrosion environments during service, requiring nickel-based single-crystal superalloys to have excellent high-temperature creep resistance and long-term structural stability during long-term high-temperature service.

[0003] Since their introduction in the 1970s, nickel-based single-crystal superalloys have undergone a development process from first-generation, second-generation, third-generation, and subsequent novel single-crystal superalloys. With the continuous development of alloy design concepts and strengthening mechanisms, single-crystal superalloys have achieved continuous improvements in service temperature and high-temperature creep performance by increasing the content of refractory elements, optimizing the γ / γ′ two-phase microstructure, and controlling the distribution behavior of alloying elements. Currently, first- and second-generation nickel-based single-crystal superalloys have achieved large-scale engineering applications and are widely used in key hot-end components such as aero-engines and gas turbine blades. Third-generation nickel-based single-crystal superalloys, due to the introduction of higher rhenium (Re) content, have significant advantages in high-temperature creep performance, but also suffer from increased alloy density, high cost, severe solidification segregation, and TCP phase precipitation during long-term service, which limits their engineering applications. Fourth- to sixth-generation single-crystal superalloys are currently mainly in the experimental research and performance exploration stage and have not yet achieved mature large-scale engineering applications.

[0004] Currently, research on advanced single-crystal superalloys both domestically and internationally primarily focuses on optimizing second- and third-generation alloy systems. Traditional second-generation single-crystal superalloys typically contain approximately 7–10 wt.% Co and 3 wt.% Re. While possessing good overall performance and a solid foundation for engineering applications, their high-temperature creep performance is limited by the content of strengthening elements, making it difficult to meet the demands of next-generation high thrust-to-weight ratio aero-engines and high-temperature gas turbines for higher service temperatures and longer lifespans. Therefore, how to further improve the high-temperature mechanical properties of single-crystal superalloys while reducing the content of precious elements, controlling alloy density, and improving microstructure stability has become a critical technical challenge that urgently needs to be addressed in the field of advanced single-crystal superalloys. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal superalloy, its preparation method and application, which has good long-term structural stability; the high-temperature creep life is improved, especially the creep performance under high temperature and low stress above 950℃.

[0006] This invention provides a low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal superalloy, comprising the following elements by mass fraction:

[0007] Cr 1.5~3.0%, Co 2.0~4.0%, W 6.0~8.0%, Mo 0.5~2.0%, Ta 6.5~8.5%, Re 3.5~4.8%, Al 5.2~6.5%, Ti 0~0.4%, Hf 0~0.15%, balance Ni.

[0008] In one specific embodiment of the present invention, Cr 1.8~3.0%, Co 2.0~3.5%, W 6.5~7.5%, Mo 0.5~1.5%, Ta 7.0~8.0%, Re 3.8~4.5%, Al 5.5~6.2%, Ti 0~0.3%, and Hf 0~0.10%.

[0009] In one specific embodiment of the present invention, Co / Re ≤ 0.9, W + Ta + Re ≥ 17 wt.%.

[0010] In one specific embodiment of the present invention, the area ratio of the TCP phase after the alloy is exposed to heat at 1100℃ for 1000h is ≤0.5%.

[0011] In one specific embodiment of the present invention, the γ′ phase accounts for 60-70% of the volume of the alloy, and the γ′ phase has a cubic structure.

[0012] In one specific embodiment of the present invention, the alloy specifically comprises Cr 2.0%, Co 3.3%, W 7.5%, Mo 0.7%, Ta 7.0%, Re 3.9%, Al 5.9%, Ti 0.2%, Hf 0.1%, with the balance being Ni;

[0013] Or it may include Cr 2.0%, Co 3.3%, W 6.5%, Mo 2.0%, Ta 7.0%, Re 3.9%, Al 6.0%, Ti 0.2%, Hf 0.1%, with the balance being Ni;

[0014] It may include Cr 2.0%, Co 3.3%, W 6.5%, Mo 2.0%, Ta 7.0%, Re 3.9%, Al 5.8%, Ti 0.2%, Hf 0.1%, with the balance being Ni.

[0015] This invention provides a method for preparing the low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal superalloy described in the above-mentioned technical solution, comprising the following steps:

[0016] The raw materials are vacuum induction melted into master alloy ingots, and then single crystal casting test bars are prepared by directional solidification process.

[0017] The single-crystal casting test rod was subjected to solution treatment and aging heat treatment to obtain a low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal high-temperature alloy.

[0018] In one specific embodiment of the present invention, the solution treatment temperature is 1230~1360℃, and the holding time is 16~28h.

[0019] In one specific embodiment of the present invention, the aging heat treatment includes a first-stage aging heat treatment and a second-stage aging heat treatment;

[0020] The temperature of the first-stage aging heat treatment is 1100~1160℃, and the holding time is 1~4h;

[0021] The temperature of the secondary aging heat treatment is 850~900℃, and the holding time is 16~24h.

[0022] This invention provides an application of the low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal superalloy described above in aero-engine or gas turbine turbine blades.

[0023] This invention provides a low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal superalloy, comprising the following elements by mass fraction: Cr 1.5~3.0%, Co 2.0~4.0%, W 6.0~8.0%, Mo 0.5~2.0%, Ta 6.5~8.5%, Re 3.5~4.8%, Al 5.2~6.5%, Ti 0~0.4%, Hf 0~0.15%, with the balance being Ni. Under the combined effect of the above-mentioned components, this alloy exhibits good long-term structural stability; its high-temperature creep life is improved, particularly its creep performance under 1050 ℃ / 190 MPa creep conditions. Attached Figure Description

[0024] Figure 1 Microstructure image of the alloy prepared in Example 1 after long-term aging at 1100 °C for 1000 h;

[0025] Figure 2 Microstructure image of the alloy prepared in Example 2 after long-term aging at 1100 °C for 1000 h;

[0026] Figure 3 Microstructure image of the alloy prepared in Example 3 after long-term aging at 1100 °C for 1000 h;

[0027] Figure 4 The image shows the metallographic structure of the alloy prepared in Example 1 in the as-cast state;

[0028] Figure 5 The image shows the metallographic structure of the alloy prepared in Example 2 in the as-cast state;

[0029] Figure 6 The image shows the metallographic structure of the alloy prepared in Example 3 in the as-cast state;

[0030] Figure 7 Images showing the microstructures of the alloys prepared in Examples 1, 2, and 3 after solution heat treatment according to procedures A, B, C, and D, respectively;

[0031] Figure 8 The microstructure of the alloy prepared in Example 1 after one aging process is shown in the diagram.

[0032] Figure 9 The microstructure of the alloy prepared in Example 2 after one aging process is shown in the diagram.

[0033] Figure 10 The microstructure of the alloy prepared in Example 3 after one aging process is shown in the diagram.

[0034] Figure 11 The diagram shows the microstructure of the alloy after secondary aging, where (a) is the alloy prepared in Example 1, (b) is the alloy prepared in Example 2, and (c) is the alloy prepared in Example 3. Detailed Implementation

[0035] This invention provides a low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal superalloy, comprising the following elements by mass fraction:

[0036] Cr 1.5~3.0%, Co 2.0~4.0%, W 6.0~8.0%, Mo 0.5~2.0%, Ta 6.5~8.5%, Re 3.5~4.8%, Al 5.2~6.5%, Ti 0~0.4%, Hf 0~0.15%, balance Ni.

[0037] The low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal superalloy provided by this invention contains 1.5-3.0% Cr, specifically 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, or 3.0%; preferably 1.8-3.0%.

[0038] The low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal superalloy provided by this invention comprises 2.0~4.0% Co, specifically 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9% or 4.0%; preferably 2.0~3.5%.

[0039] The low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal superalloy provided by this invention comprises 6.0~8.0% W, and the specific content can be 6.0%, 6.1%, 6.2%, 6.3%, 6.4%, 6.5%, 6.6%, 6.7%, 6.8%, 6.9%, 7.0%, 7.1%, 7.2%, 7.3%, 7.4%, 7.5%, 7.6%, 7.7%, 7.8%, 7.9% or 8.0%; preferably 6.5~7.5%.

[0040] The low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal superalloy provided by the present invention comprises 0.5~2.0% Mo, and the specific content can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7% or 1.8%; preferably 0.5~1.5%.

[0041] The low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal superalloy provided by this invention comprises 6.5-8.5% Ta, specifically 6.5%, 6.6%, 6.7%, 6.8%, 6.9%, 7.0%, 7.1%, 7.2%, 7.3%, 7.4%, 7.5%, 7.6%, 7.7%, 7.8%, 7.9%, 8.0%, 8.1%, 8.2%, 8.3%, 8.4%, and 8.5%, preferably 7.0-8.0%.

[0042] The low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal superalloy provided by this invention contains 3.5-4.8% Re, and the specific content can be 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, or 4.8%; preferably 3.8-4.5%.

[0043] In this invention, Co / Re ≤ 0.9, specifically 0.9, 0.85, 0.8, 0.75, 0.70, 0.65, 0.6, 0.55, 0.5, 0.45, 0.4, 0.35, 0.3, 0.25, 0.2, 0.15 or 0.1.

[0044] In this invention, W+Ta+Re≥17 wt.%, specifically 18.4% or 17.4%.

[0045] The low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal superalloy provided by this invention comprises 5.2-6.5% Al, specifically 5.2%, 5.3%, 5.4%, 5.5%, 5.6%, 5.7%, 5.8%, 5.9%, 6.0%, 6.1%, 6.2%, 6.3%, 6.4%, or 6.5%; preferably 5.5-6.2%.

[0046] The low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal superalloy provided by the present invention includes Ti of 0~0.4%, specifically 0%, 0.1%, 0.2%, 0.3% or 0.4%, preferably 0~0.3%.

[0047] The low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal superalloy provided by this invention comprises 0~0.15% Hf, and the specific content can be 0%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, 0.12%, 0.13%, 0.14% or 0.15%, preferably 0~0.10%.

[0048] The low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal superalloy provided by this invention includes the balance Ni.

[0049] The low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal superalloy provided by this invention specifically comprises Cr 2.0%, Co 3.3%, W 7.5%, Mo 0.7%, Ta 7.0%, Re 3.9%, Al 5.9%, Ti 0.2%, Hf 0.1%, with the balance being Ni;

[0050] Or it may include Cr 2.0%, Co 3.3%, W 6.5%, Mo 2.0%, Ta 7.0%, Re 3.9%, Al 6.0%, Ti 0.2%, Hf 0.1%, with the balance being Ni;

[0051] The alloy may contain 2.0% Cr, 3.3% Co, 6.5% W, 2.0% Mo, 7.0% Ta, 3.9% Re, 5.8% Al, 0.2% Ti, and 0.1% Hf, with the balance being Ni. The low-cobalt, rhenium-modified second-generation nickel-based single-crystal superalloy provided by this invention exhibits a topologically harmful (TCP) phase area ratio of ≤0.5% after heat exposure at 1100℃ for 1000h. The γ′ phase accounts for 60-70% of the volume in the alloy and exhibits a cubic structure.

[0052] This invention also provides a method for preparing the low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal superalloy described in the above technical solution, comprising the following steps:

[0053] The raw materials are vacuum induction melted into master alloy ingots, and then single crystal casting test bars are prepared by directional solidification process.

[0054] The single-crystal casting is subjected to solution treatment and aging heat treatment to obtain a low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal high-temperature alloy.

[0055] In this invention, the solution treatment temperature is 1230~1360℃, specifically 1230℃, 1240℃, 1250℃, 1260℃, 1270℃, 1280℃, 1290℃, 1300℃, 1310℃, 1320℃, 1330℃, 1340℃, 1350℃ or 1360℃; the heat preservation time is 16~28h, specifically 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h, 25h, 26h, 27h or 28h.

[0056] In this invention, the aging heat treatment includes a primary aging heat treatment and a secondary aging heat treatment; the temperature of the primary aging heat treatment is 1100~1160℃, specifically 1100℃, 1110℃, 1120℃, 1130℃, 1140℃, 1150℃ or 1160℃; the holding time is 1~4h, specifically 1h, 2h, 3h or 4h; the temperature of the secondary aging heat treatment is 850~900℃, specifically 850℃, 860℃, 870℃, 880℃, 890℃ or 900℃; the holding time is 16~24h, specifically 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h or 24h.

[0057] This invention provides an application of the low-cobalt, rhenium-modified second-generation nickel-based single-crystal superalloy described above in turbine blades of aero-engines or gas turbines.

[0058] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, of a low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal high-temperature alloy, its preparation method, and its applications, should not be construed as limiting the scope of protection of the present invention.

[0059] Examples 1-3

[0060] The raw materials are vacuum induction melted into a master alloy, which is then directionally solidified to obtain a single-crystal casting.

[0061] The single-crystal casting is subjected to solution treatment and aging heat treatment to obtain a low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal high-temperature alloy.

[0062] Table 1 shows the composition of the alloys prepared in Examples 1-3.

[0063] Table 1

[0064]

[0065] Figures 1-3 The images show the microstructure of the alloys prepared in Examples 1, 2, and 3 after long-term aging at 1100 °C for 1000 h, respectively; where (a) to (j) are microstructure images after aging for 100 h, 200 h, 300 h, 400 h, 500 h, 600 h, 700 h, 800 h, 900 h, and 1000 h, respectively. Figures 1-3 It can be seen that although fine white flaky precipitates formed in the three alloys during long-term aging, no long needle-like TCP phase was observed to precipitate.

[0066] Figures 4-6 These are metallographic images of the alloys in the as-cast state, representing Examples 1, 2, and 3, respectively; from... Figures 4-6 As can be seen, the cast alloys all exhibit obvious dendritic morphology, and there is also a bright white eutectic structure in the interdendritic region.

[0067] In order to eliminate the residual eutectic, significant elemental segregation and coarse γ′ phase structure present in the as-cast alloy, this invention explored and formulated four different solution treatment regimes, and the specific solution temperature and holding time are listed in Table 2. Figure 7 Images show the microstructures of the alloys prepared in Examples 1, 2, and 3 after solution heat treatment according to procedures A, B, C, and D, respectively. (a) to (d) represent the alloy prepared in Example 1, (e) to (h) represent the alloy prepared in Example 2, and (i) to (l) represent the alloy prepared in Example 3. Figure 7 As can be seen, after treatment A, the dendrite morphology of the three alloys is obvious, and a large amount of residual eutectic still exists; after treatments B and C, the dendrite morphology is no longer obvious, and the residual eutectic content is greatly reduced. In particular, after treatment C, only a small amount of eutectic structure exists between dendrites; finally, after treatment D, the residual eutectic is completely eliminated, and the dendrite morphology is no longer clearly visible, indicating that sufficient diffusion has occurred between dendrites and between dendritic elements, which significantly reduces the elemental segregation of the alloy.

[0068] Table 2

[0069]

[0070] The morphology and size of the γ′ phase have a significant impact on the alloy properties. To control the morphology and size of the γ′ phase, an aging treatment is required. Since the morphology and size of the γ′ phase are influenced by both aging temperature and aging time, this study designed an orthogonal experiment, setting four temperatures (1100 ℃, 1120 ℃, 1140 ℃, and 1160 ℃) and four holding times (1 h, 2 h, 3 h, and 4 h). Through permutations and combinations, 16 different aging regimes were obtained, and the specific aging regimes are listed in Table 3.

[0071] Table 3

[0072]

[0073] After orthogonal experiments, the primary aging regime for the alloy prepared in Example 1 was determined to be 1160℃ / 3 h, for the alloy prepared in Example 2 it was 1120℃ / 3 h, and for the alloy prepared in Example 3 it was 1160℃ / 1 h. The secondary aging regime for all three alloys was uniformly set at 870℃ / 20 h. Figures 8-10 The diagrams are for the first aging of alloys in Examples 1, 2, and 3, respectively. Among them, (a1) to (d1) are for the first aging at 1100℃ for aging times of 1h, 2h, 3h, and 4h, respectively; (a2) to (d2) are for the first aging at 1120℃ for aging times of 1h, 2h, 3h, and 4h, respectively; (a3) ​​to (d3) are for the first aging at 1140℃ for aging times of 1h, 2h, 3h, and 4h, respectively; and (a4) to (d4) are for the first aging at 1160℃ for aging times of 1h, 2h, 3h, and 4h, respectively. Figure 11 The images show the microstructure of the alloys prepared in Examples 1, 2, and 3 after secondary aging.

[0074] Creep tests were conducted under four different temperature and stress conditions: 760 ℃ / 620 MPa, 930 ℃ / 350 MPa, 980 ℃ / 248 MPa, and 1050 ℃ / 190 MPa. The creep life of the three alloys from the embodiments and the commercial second-generation single-crystal DD5 alloy at 1% creep strain was obtained, as shown in Table 4. It can be seen that the three alloys from the embodiments outperformed the second-generation single-crystal DD5 alloy under all four different creep conditions. The alloy prepared in Example 2 showed superior overall performance, especially at 980 ℃ and 1050 ℃, significantly outperforming the alloys of Examples 1 and 3. Comparing Example 2 and the second-generation single-crystal DD5 alloy, the most significant change was the increase in rhenium content from 3% to 3.9%. By appropriately balancing other elements, the creep performance almost doubled under a wide range of temperature and stress conditions. Furthermore, no significant long needle-like TCP precipitation was observed after 1100 ℃ / 1000 hours of high-temperature heat exposure. The alloys provided by this invention offer high cost-effectiveness and significant application value.

[0075] Table 4

[0076]

[0077] As shown in the above examples, the low-cobalt, rhenium-modified second-generation nickel-based single-crystal superalloy comprises, by mass fraction, the following elements: Cr 1.5~3.0%, Co 2.0~4.0%, W 6.0~8.0%, Mo 0.5~2.0%, Ta 6.5~8.5%, Re 3.5~4.8%, Al 5.2~6.5%, Ti 0~0.4%, Hf 0~0.15%, with the balance being Ni. Under the combined effect of the above-mentioned components, this alloy exhibits good long-term structural stability; its high-temperature creep life is improved, especially its creep performance under 1050 ℃ / 190 MPa creep conditions.

[0078] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A low cobalt, medium rhenium modified second generation nickel-base single crystal superalloy characterized in that, In terms of quality fraction, it includes the following elements: Cr 1.5~3.0%, Co 2.0~4.0%, W 6.0~8.0%, Mo 0.5~2.0%, Ta 6.5~8.5%, Re 3.5~4.8%, Al 5.2~6.5%, Ti 0~0.4%, Hf 0~0.15%, balance Ni.

2. The low cobalt, medium rhenium modified second generation nickel-base single crystal superalloy of claim 1, wherein, Cr1.8~3.0%, Co 2.0~3.5%, W 6.5~7.5%, Mo 0.5~1.5%, Ta 7.0~8.0%, Re 3.8~4.5%, Al 5.5~6.2%, Ti 0~0.3%, Hf 0~0.10%.

3. The low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal superalloy according to claim 1, characterized in that, Co / Re≤0.9, W+Ta+Re≥17 wt.%.

4. The low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal superalloy according to claim 1, characterized in that, The area ratio of the TCP phase in the alloy after heat exposure at 1100℃ for 1000h is ≤0.5%.

5. The low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal superalloy according to claim 1, characterized in that, The γ′ phase accounts for 60-70% of the volume of the alloy and has a cubic structure.

6. The low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal superalloy according to claim 1, characterized in that, The alloy specifically comprises Cr 2.0%, Co 3.3%, W 7.5%, Mo 0.7%, Ta 7.0%, Re 3.9%, Al 5.9%, Ti 0.2%, Hf 0.1%, with the balance being Ni; It may include Cr 2.0%, Co 3.3%, W 6.5%, Mo 2.0%, Ta 7.0%, Re 3.9%, Al 6.0%, Ti 0.2%, Hf 0.1%, with the balance being Ni; It may include Cr 2.0%, Co 3.3%, W 6.5%, Mo 2.0%, Ta 7.0%, Re 3.9%, Al 5.8%, Ti 0.2%, Hf 0.1%, with the balance being Ni.

7. A method for preparing the low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal superalloy as described in claim 1, characterized in that, Includes the following steps: The raw materials are vacuum induction melted into master alloy ingots, and then single crystal casting test bars are prepared by directional solidification process. The single-crystal casting test bar was subjected to solution treatment and aging heat treatment to obtain a low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal high-temperature alloy.

8. The preparation method according to claim 7, characterized in that, The solution treatment temperature is 1230~1360℃, and the holding time is 16~28h.

9. The preparation method according to claim 7, characterized in that, Aging heat treatment includes primary aging heat treatment and secondary aging heat treatment; The temperature of the first-stage aging heat treatment is 1100~1160℃, and the holding time is 1~4h; The temperature of the secondary aging heat treatment is 850~900℃, and the holding time is 16~24h.

10. The application of the low-cobalt, medium-rhenium improved second-generation nickel-based single-crystal superalloy as described in any one of claims 1 to 6 in turbine blades of aero-engines or gas turbines.

Images