A Co-Ni-based superalloy with a stable γ / γ′ dual FCC phase coherent structure and high-temperature oxidation resistance, and its preparation method.

Abstract

This invention discloses a Co-Ni-based superalloy with a stable γ / γ′ dual FCC phase coherent structure and high-temperature oxidation resistance. Its composition, by mass percentage, is: Ni 20.0–40.0%, Al 3.0–8.0%, V 2.0–5.0%, Ta 8.0–14.0%, Ti 1.0–4.0%, Cr 5.0–12.0%, with the remainder being Co. The Co-Ni-based superalloy prepared by this invention exhibits a room temperature compressive strength of 629.5–860.4 MPa and an oxidation rate reaching 2.98 × 10⁻⁶ MPa. ‑8 g 2 / (cm 4 ·s) and above, in Co-based superalloys, there is a stable γ / γ′ dual FCC phase structure, the γ′ phase particle size is below 200nm, there is an ultrafine γ′ phase structure, good strength and toughness, low density, and excellent high-temperature oxidation resistance. It can be used in key components in aerospace, petrochemical, nuclear power generation and other fields. This invention provides a preparation method for the superalloy material, which is simple and conducive to large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature alloy preparation technology, specifically relating to a Co-Ni-based high-temperature alloy with a stable γ / γ′ dual FCC phase coherent structure and high-temperature oxidation resistance, and its preparation method. Background Technology

[0002] With the increasing demands for inlet temperature and pressure in the hot zones of turbine engines, the materials used in these zones require higher high-temperature mechanical properties and oxidation resistance. Ni-based superalloys, due to the Ni3Al-γ′ phase in the γ-Ni matrix hindering dislocation movement and enhancing the alloy's high-temperature strength, are widely used in hot zone materials in aerospace, petrochemical, and nuclear power generation fields. In contrast, Co-based superalloys, lacking a stable γ′ phase structure at high temperatures, have not been widely adopted.

[0003] In the prior art, after J. Sato et al. discovered the stable Co3(Al,W)-γ′ phase in Co-Al-W alloys in 2006, scholars have conducted a series of studies on the γ / γ′ coherent phase of alloying elements in Co-based superalloys. However, the development of Co-Al-W based superalloys is limited in meeting the problem of lightweighting due to their high density (J. Sato, T. Omori, K. Oikawa, I. Ohnuma, R. Kainuma, K. Ishida, Science 2006; 312: 90-91). Chen et al. developed a novel high-melting-point, high-strength Co-Al-V-based superalloy with V replacing W. It also has a Co3(Al,V)-γ′ structure and exhibits good performance in high-temperature creep resistance. It also shows better prospects in terms of alloy strength and lightweight development, providing a research direction for the high-temperature strength problem of Co-based superalloys (Y. Chen, C. Wang, J. Ruan, T. Omori, R. Kainuma, K. Ishida, X. Liu, Acta Materialia 2019; 170: 62-74).

[0004] The high-temperature oxidation resistance of alloys is an important factor affecting the service life of workpieces. Since Co-based superalloys have better high-temperature oxidation resistance than Ni-based superalloys, and Co has a higher melting point than Ni, Co-based superalloys have good prospects. Therefore, it is necessary to study the oxidation behavior of Co-based superalloys and the influence of alloying elements on their oxidation resistance. A continuous Al2O3 oxide layer is the key to improving the oxidation resistance of superalloys, as it can effectively prevent further oxidation of the matrix.

[0005] Directional solidification is an essential casting method for preparing single-crystal turbine blades. Single crystals exhibit better mechanical properties and high-temperature creep resistance in the growth direction. Furthermore, using directional solidification to further process the alloy through solution aging can improve production efficiency and has promising application prospects.

[0006] Co-Ni-Al-V based superalloys show promising high-temperature mechanical properties, but the addition of V reduces their oxidation resistance. Therefore, improving the high-temperature oxidation resistance of Co-based superalloys while maintaining stable microstructure and good mechanical properties is of great significance. Summary of the Invention

[0007] The purpose of this invention is to provide a Co-Ni-based superalloy with a stable γ / γ′ dual FCC phase coherent structure and high-temperature oxidation resistance, and its preparation method. By combining alloy composition design with innovative heat treatment process, the invention solves the problems of poor oxidation resistance and low strength of cobalt-nickel-based alloys mentioned in the background art. The prepared Co-Ni-based superalloy has good microstructure uniformity and stability, excellent oxidation resistance, and good application prospects.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] This invention provides a Co-Ni-based superalloy with a stable γ / γ′ dual FCC phase coherent structure and high-temperature oxidation resistance. Its composition by mass percentage is: Ni 20.0~40.0%, Al 3.0~10.0%, V 2.0~7.0%, Ta 4.0~14.0%, Ti 1.0~5.0%, Cr 5.0~15.0%, with the remainder being Co.

[0010] In a preferred embodiment, the composition of the Co-Ni-based superalloy, by mass percentage, is as follows:

[0011] Ni 25.0~35.0%, Al 4.0~6.0%, V 3.0~5.0%, Ta 5.0~12.0%, Ti 1.0~3.0%, Cr 5.0~12.0%, the remainder is Co.

[0012] Further preferably, the Co-Ni-based superalloy has the following composition by atomic percentage: CoNiAlVTaTi 87.0~95.0%, Cr 5.0~13.0%.

[0013] In a preferred embodiment, the Co-Ni-based superalloy has an FCC+FCC coherent dual-phase structure, wherein there is a dispersed Laves phase reinforcement between dendrites.

[0014] The present invention also provides a method for preparing the Co-Ni-based superalloy, comprising the following steps:

[0015] S1. Alloy melting: The raw materials are batched according to atomic percentage. Inert gas is introduced during the melting process and positive pressure is maintained. After the melting is completed, a small current is maintained to help the alloy feed and prevent the alloy from cooling too quickly and forming pores, so as to obtain Co-Ni based high temperature alloy ingots.

[0016] S2. Directional solidification treatment: The Co-Ni-based high-temperature alloy ingot obtained in step S1 is loaded into a directional solidification melting furnace, the alloy is heated to above the melting point and then directional solidification treatment is performed to obtain the directional solidified alloy.

[0017] S3. Graded heat treatment: The alloy obtained in step S2 after directional solidification is put back into the directional solidification melting furnace, heated to the solution temperature and held at that temperature, then slowly cooled to the aging temperature, held at that temperature for a predetermined time and then drawn to obtain the Co-Ni-based high-temperature alloy.

[0018] In step S1, the vacuum level is maintained at 5×10 during the smelting process. -4 Below Pa, after all raw materials have melted, the molten metal is refined to ensure uniform composition. The current during refining is 120~140 A, and the refining time is 1~5 min each time. It is remelted at least 3 times. After refining, Co-Ni based high temperature alloy ingot is obtained.

[0019] In step S2, the alloy is heated to 1500~1600 ℃ and held for 10~60 min. After holding, it is pulled at a constant speed of 500~1000 μm / min. The quenching medium for pulling is Ga-In-Sn, and the Ga-In-Sn alloy is in the mass ratio of Ga 60~70%, In 10~20%, and Sn 10~20%.

[0020] In step S3, specifically:

[0021] The temperature is heated to a solution temperature of 1200~1250 ℃, and the solution holding time is 2~10 h. The solution treatment is carried out continuously in a directional solidification furnace to homogenize the alloy.

[0022] The alloy was slowly cooled to the aging temperature at a cooling rate of 10~20 ℃ / min. The aging heat treatment temperature was 800~900 ℃, and the holding time was 50~100 h. After the holding time, directional drawing was performed. The aging treatment was a continuous aging treatment to ensure that an aged microstructure was obtained.

[0023] The directional pulling process uses uniformly accelerated pulling with a pulling speed of 1000~10000 μm / min.

[0024] During the graded heat treatment process, the alloy is subjected to directional cooling treatment and continuous solution aging to ensure uniform alloy structure, resulting in a dendritic structure with (0 0 1) orientation.

[0025] Compared with the prior art, the beneficial technical effects of the present invention are as follows: During cyclic oxidation at 900℃, a double Al2O3 protective layer was observed in the oxide layer of the alloy of the present invention. Over time, the oxide layer thickens, the oxidation resistance improves, and the oxidation weight gain can reach 2.98 × 10⁻⁶. -8 g 2 / cm 4 / s and above.

[0026] This invention, by adding Cr, inhibits the formation of CoO and promotes the formation of a dense Al2O3 oxide film, resulting in excellent high-temperature oxidation resistance in high-temperature alloys that do not contain rare earth elements.

[0027] This invention also exhibits excellent mechanical properties. Furthermore, due to its γ / γ′ biphase coherent structure being extremely stable at 800~1000 ℃ and possessing an ultrafine γ′ phase structure with γ′ phase particles having a particle size of less than 200 nm, the compressive strength at room temperature can reach up to 860.4 MPa, demonstrating excellent mechanical and thermal stability. Attached Figure Description

[0028] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings.

[0029] Figure 1 The image shows a comparison of the casting structure and the directional solidification structure in Example 1 using electron microscopy.

[0030] Figure 2 Electron micrographs of the γ′ crystal phase structure of the Co-Ni-Al-V-Ta-Ti-Cr high-temperature alloy in the examples and comparative examples.

[0031] Figure 3 The images show the XRD patterns of the Co-Ni-Al-V-Ta-Ti-Cr high-temperature alloys in the examples and comparative examples.

[0032] Figure 4 Electron micrographs of the Co-Ni-Al-V-Ta-Ti-Cr high-temperature alloys in the examples and comparative examples.

[0033] Figure 5 The oxidation curves of the Co-Ni-Al-V-Ta-Ti-Cr high-temperature alloys in the examples and comparative examples are shown.

[0034] Figure 6 The XRD patterns of the Co-Ni-Al-V-Ta-Ti-Cr superalloys in the examples and comparative examples after 100 hours of oxidation are shown.

[0035] Figure 7 The oxidation surface of the Co-Ni-Al-V-Ta-Ti-Cr high-temperature alloy after 100 hours of oxidation is shown in the examples and comparative examples.

[0036] Figure 8 This is an oxidation cross-sectional view of the Co-Ni-Al-V-Ta-Ti-Cr high-temperature alloy in the examples and comparative examples after 100 hours of oxidation.

[0037] Figure 9 The transmission electron microscope (TEM) bright-field phase and diffraction spots in Example 1 demonstrate that the γ / γ′ phase is a coherent structure. Detailed Implementation

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific implementations. The following examples are implemented under the premise of the technical solutions of the present invention, providing detailed implementation methods and specific operating procedures, which will help those skilled in the art to further understand the present invention. It should be noted that the scope of protection of the present invention is not limited to the following embodiments; any adjustments and improvements made under the concept of the present invention shall fall within the scope of protection of the present invention.

[0039] This invention provides a Co-Ni-based superalloy with a stable γ / γ′ dual FCC phase coherent structure and high-temperature oxidation resistance. Its composition by mass percentage is: Ni 20.0~40.0%, Al 3.0~10.0%, V 2.0~7.0%, Ta 4.0~14.0%, Ti 1.0~5.0%, Cr 5.0~15.0%, with the remainder being Co.

[0040] The Co-Ni-based superalloy of this invention possesses excellent high-temperature oxidation resistance. Based on a Co-Al-V superalloy system, this system is not only low-cost but also low-density, exhibiting superior performance. By adding Ni, Ta, and Ti, a stable γ / γ′ dual FCC phase region can be obtained, improving both microstructure stability and strength. Experiments have confirmed that the alloy maintains microstructure stability at 800-1000℃. The inventors discovered that both Ni and Al can improve the high-temperature oxidation resistance of the alloy material. Furthermore, Ni has a similar atomic radius to Co and its properties are similar, preventing significant lattice distortion and thus contributing greatly to microstructure stability. The addition of Ti further enhances microstructure stability and strength, and at high temperatures, it forms TiTaO4, further increasing high-temperature oxidation resistance. Cr is also an important element for improving the high-temperature oxidation resistance of Co-Al-V-based superalloys. The addition of Cr promotes the formation and aggregation of Al2O3, and can form a Cr2O3 healing layer, creating a dense protective layer.

[0041] Preferably, the composition of the Co-Ni-based superalloy is as follows by mass percentage: Ni 25.0~35.0%, Al 4.0~6.0%, V 3.0~5.0%, Ta 5.0~12.0%, Ti 1.0~3.0%, Cr 5.0~12.0%, with the remainder being Co.

[0042] More preferably, the composition of the Co-Ni-based superalloy by mass percentage is: Ni 28.0~32.0%, Al 4.0~5.0%, V 4.0~5.0%, Ta 5.0~10.0%, Ti 1.0~2.0%, Cr 7.0~12.0%, with the remainder being Co.

[0043] Preferably, the Co-Ni-based superalloy has the following composition by atomic percentage: CoNiAlVTaTi 87.0~95.0% and Cr 5.0~13.0%.

[0044] More preferably, the Co-Ni-based superalloy has the following composition by atomic percentage: CoNiAlVTaTi 87.0~92.5%, Cr 7.5~13.0%.

[0045] Preferably, the Co-Ni-based superalloy has an FCC+FCC coherent dual-phase structure, wherein there is a dispersed Laves phase reinforcement between dendrites.

[0046] The Co-Ni-based high-temperature alloy provided by this invention, by designing the material composition and adding alloying elements (Ta and Ti elements) that can form Laves phase between dendrites to the matrix material, and by heat treating the alloy, can obtain a uniformly dispersed microstructure. This alloy has excellent processing performance, and complex workpieces can be obtained by casting. Due to its stable coherent microstructure at high temperatures, it also has excellent mechanical properties at high temperatures.

[0047] This invention improves the strength of the alloy by adjusting the Ta element content to control the proportion of the Laves phase.

[0048] The Co-Ni-based high-temperature alloy provided by this invention requires strict control of the Cr content. If the Cr content is too low, the improvement of the high-temperature alloy's oxidation resistance is limited, and the heat-treated microstructure is coarse and the strength is insufficient, which cannot meet the application requirements. If the Cr content is too high, the precipitation of the Laves phase increases, and a small amount of Cr will volatilize during the melting process, causing pores in the alloy and affecting the alloy's oxidation resistance.

[0049] The present invention also provides a method for preparing the Co-Ni-based superalloy, comprising the following steps:

[0050] S1. Alloy melting: The raw materials are batched according to atomic percentage, and a non-consumable vacuum arc melting furnace is used. Argon gas is introduced during the melting process and positive pressure is maintained. After the melting is completed, a small current is maintained to help the alloy feed and prevent the alloy from cooling too quickly and forming pores, so as to obtain Co-Ni based high temperature alloy ingots.

[0051] S2. Directional solidification treatment: The Co-Ni-based high-temperature alloy ingot obtained in step S1 is loaded into a directional solidification melting furnace, the alloy is heated to above the melting point and then directional solidification treatment is performed to obtain the directional solidified alloy.

[0052] S3. Graded heat treatment: The alloy obtained in step S2 after directional solidification is put back into the directional solidification melting furnace, heated to the solution temperature and held at that temperature, then slowly cooled to the aging temperature, held at that temperature for a predetermined time and then drawn to obtain the Co-Ni-based high-temperature alloy.

[0053] In step S1, the vacuum level is maintained at 5×10 during the smelting process. -4 Below Pa, after all raw materials have melted, the molten metal is refined to ensure uniform composition. The current during refining is 120~140 A, and the refining time is 1~5 min each time. It is remelted at least 3 times. After refining, Co-Ni based high temperature alloy ingot is obtained.

[0054] Furthermore, in step S1, the alloying materials need to be pre-treated before batching, for example, by sanding off the oxide layer on the surface and cleaning with anhydrous ethanol to ensure that the surface of the raw materials is free of oil and dust.

[0055] Furthermore, in step S1, a non-consumable vacuum arc melting furnace is used. During the melting process, in a top-down order, a staged melting method is adopted. First, V, Co, Al, Ni, Ta, Ti, and Cr are placed into the vacuum arc melting furnace in sequence, a protective atmosphere is introduced, and the pressure of the vacuum arc melting furnace is adjusted to positive pressure. Then, an electric arc is generated by current and is 1-3 mm above the surface of Cr for melting. After melting ≥3 times, the alloy ingot and Al are placed in and melted again ≥3 times according to the same steps to obtain a high-temperature alloy.

[0056] The non-consumable vacuum arc melting furnace used in this invention is easy to operate, requires a small amount of alloy weight for melting, which is beneficial for production. The melting time is short, and the alloy performance can be verified in a short time.

[0057] Furthermore, in step S1, during the smelting process, since the V element is in powder form, the metal raw material completely covers the V powder. Due to the volatility of the Cr element, the initial smelting current should not be too high, preferably 110~120 A. Subsequently, due to the refractory properties of the Ta element, in order to ensure uniform alloy melting, the current should be adjusted to above 140 A.

[0058] Furthermore, in step S1, a vacuum of 5 × 10⁻⁶ is drawn into the vacuum arc melting furnace. -4 Pa, then fill with high-purity argon gas and maintain positive pressure.

[0059] In step S2, the alloy is heated to 1500~1600 ℃ and held for 10~60 min. After holding, it is pulled at a constant speed of 500~1000 μm / min. The quenching medium for pulling is Ga-In-Sn alloy, and the mass ratio of Ga-In-Sn alloy is 60~70% Ga, 10~20% In and 10~20% Sn.

[0060] Furthermore, in step S2, the alloy is heated to 100~200 ℃ above its melting point to ensure a large temperature gradient, and the pulling speed is 500~1000 μm / min.

[0061] In step S3, specifically:

[0062] The temperature is heated to a solution temperature of 1200~1250 ℃, and the solution holding time is 2~10 h. The solution treatment is carried out continuously in a directional solidification furnace to homogenize the alloy.

[0063] The alloy was slowly cooled to the aging temperature at a cooling rate of 10~20 ℃ / min. The aging heat treatment temperature was 800~900 ℃, and the holding time was 50~100 h. After the holding time, directional drawing was performed. The aging treatment was a continuous aging treatment to ensure that an aged microstructure was obtained.

[0064] The directional pulling process uses uniformly accelerated pulling with a pulling speed of 1000~10000 μm / min.

[0065] Furthermore, in step S3, the vacuum level is maintained at 2×10⁻⁶ during solution heat treatment. -3 Below Pa.

[0066] Furthermore, in step S3, during the graded heat treatment process, the alloy is subjected to directional cooling treatment and continuous solid solution aging to ensure uniform alloy structure, resulting in a dendritic structure with (0 0 1) orientation.

[0067] Furthermore, in step S3, a directional solidification furnace is used for remelting, which, compared to an electric arc melting furnace, exhibits a (0 0 1) oriented dendritic structure and reduces defects such as pores, resulting in a more uniform microstructure. Specifically, as shown... Figure 1 As shown.

[0068] All raw materials used in the embodiments of this application can be obtained from commercial channels.

[0069] The following embodiments are intended to further illustrate the content of the present invention, but not to limit the scope of protection of the present invention. Example 1

[0070] Co-30Ni-10Al-5V-4Ta-2Ti-8Cr(at%) alloy

[0071] Step 1: Alloy Preparation

[0072] High-purity metal materials were used, and the batches were prepared according to atomic ratios, with a total batch mass of 20 g. The alloy was melted at least five times in a non-consumable vacuum arc melting furnace under an argon atmosphere, with a vacuum level of at least 5 × 10⁻⁶ during evacuation. -4 Pa, during the smelting process, maintain positive pressure inside the furnace. In the early stage of smelting, adjust the current to 120-130A, and after the molten metal is completely melted, increase the current to 140-150A.

[0073] After melting, the alloy is further refined and subjected to solution heat treatment in a directional solidification furnace. The directional solidification furnace is heated to 1550℃ and held for refining. After holding at 1550℃ for 30 min, directional solidification is carried out at a uniform drawing speed of 1000 μm / min. The quenching medium is Ga-In-Sn alloy, which gives the alloy a dendritic structure with (0 0 1) orientation.

[0074] The alloy after directional solidification was reloaded into the furnace and heated to the solution heat treatment temperature to dissolve the dendritic structure and the non-uniform precipitates. The solution treatment was carried out at 1250 °C for 5 h. After the solution treatment, it was cooled to the aging heat treatment temperature at 20 °C / min. The aging heat treatment temperature was 900 °C and held for 100 h. Then, it was quenched in Ga-In-Sn at a uniformly accelerated pulling speed of 5000-8000 μm / min.

[0075] Step 2: Alloy microstructure and mechanical property testing

[0076] The microstructure and mechanical properties of the heat-treated alloy were analyzed using SEM, XRD, and a universal tensile testing machine. For XRD testing, diffraction peaks were measured at 10° / min, with a diffraction range of 10-90°. The universal tensile testing machine was used with a compression rate of 0.05 mm / min and a compression deformation of 15%. The as-cast microstructure and XRD patterns of the alloy are attached. Figure 2 , 3 As shown, the microstructure of the as-cast microstructure is as follows: Figure 4 As shown in the figure. The results show that the alloy microstructure of the present invention has a γ / γ′ coherent structure, and the results indicate that the γ′ phase can exist stably at a temperature of 900 °C. The microstructure morphology of the alloy is shown in the attached figure. Figure 2As shown in (a), after aging for 100 h, the size of the γ′ nanoparticles was approximately 280 nm. The room temperature compressive strength was measured to be 629.5 MPa using a universal tensile testing machine. The alloy was subjected to cyclic oxidation in a muffle furnace at 900 ℃ for a total oxidation time of 100 h. For each sample, the oxidation weight gain was measured by weighing five times and taking the average value to ensure data accuracy. The oxidation rate was 2.7 × 10⁻⁶. -8 g 2 / (cm 4 The oxidation weight gain curve is shown in the attached figure. Figure 5 As shown in the attached figure, the XRD pattern of the oxidized surface is as follows. Figure 6 As shown in the attached figure, the microstructure of the oxidized surface is as follows. Figure 7 As shown in (a), the microstructure of the oxide cross section is as follows. Figure 8 As shown in (a). Example 2

[0077] Co-30Ni-10Al-5V-2Ta-2Ti-8Cr(at%) alloy

[0078] Step 1: Alloy Preparation

[0079] High-purity metal materials were used, and the batches were prepared according to atomic ratios, with a total batch mass of 20 g. The alloy was melted at least five times in a non-consumable vacuum arc melting furnace under an argon atmosphere, with a vacuum level of at least 5 × 10⁻⁶ during evacuation. -4 Pa, during the smelting process, maintain positive pressure inside the furnace. In the early stage of smelting, adjust the current to 120-130A, and after the molten metal is completely melted, increase the current to 140-150A.

[0080] After melting, the alloy is further refined and subjected to solution heat treatment in a directional solidification furnace. The directional solidification furnace is heated to 1550℃ and held for refining. After holding at 1550℃ for 30 min, directional solidification is carried out at a uniform drawing speed of 1000 μm / min. The quenching medium is Ga-In-Sn alloy, which gives the alloy a dendritic structure with (0 0 1) orientation.

[0081] The alloy after directional solidification was reloaded into the furnace and heated to the solution heat treatment temperature to dissolve the dendritic structure and the non-uniform precipitates. The solution treatment was carried out at 1250 °C for 5 h. After the solution treatment, it was cooled to the aging heat treatment temperature at 20 °C / min. The aging heat treatment temperature was 900 °C and held for 100 h. Then, it was quenched in Ga-In-Sn at a uniformly accelerated pulling speed of 5000-8000 μm / min.

[0082] Step 2: Alloy microstructure and mechanical property testing

[0083] The microstructure and mechanical properties of the heat-treated alloy were analyzed using SEM, XRD, and a universal tensile testing machine. For XRD testing, diffraction peaks were measured at 10° / min, with a diffraction range of 10-90°. The universal tensile testing machine was used with a compression rate of 0.05 mm / min and a compression deformation of 15%. The as-cast microstructure and XRD patterns of the alloy are attached. Figure 2 , 3 As shown, the microstructure of the as-cast microstructure is as follows: Figure 4 As shown in the figure. The results show that the alloy microstructure of the present invention has a γ / γ′ coherent structure, and the results indicate that the γ′ phase can exist stably at a temperature of 900 °C. The microstructure morphology of the alloy is shown in the attached figure. Figure 2 As shown in (b), after aging for 100 h, the size of the γ′ nanoparticles was approximately 260 nm. The room temperature compressive strength was measured to be 750.7 MPa using a universal tensile testing machine. The alloy was subjected to cyclic oxidation in a muffle furnace at 900 ℃. For each sample, the oxidation weight gain was measured by weighing five times and taking the average value to ensure data accuracy. The total oxidation time was 100 h, and the oxidation rate was 2.98 × 10⁻⁶. -8 g 2 / (cm 4 The oxidation weight gain curve is shown in the attached figure. Figure 5 As shown in the attached figure, the XRD pattern of the oxidized surface is as follows. Figure 6 As shown in the attached figure, the microstructure of the oxidized surface is as follows. Figure 7 As shown in (b), the microstructure of the oxide cross section is as follows. Figure 8 As shown in (b). Example 3

[0084] Co-30Ni-10Al-5V-4Ta-2Ti-12Cr(at%) alloy

[0085] Step 1: Alloy Preparation

[0086] High-purity metal materials were used, and the batches were prepared according to atomic ratios, with a total batch mass of 20 g. The alloy was melted at least five times in a non-consumable vacuum arc melting furnace under an argon atmosphere, with a vacuum level of at least 5 × 10⁻⁶ during evacuation. -4 Pa, during the smelting process, maintain positive pressure inside the furnace. In the early stage of smelting, adjust the current to 120-130A, and after the molten metal is completely melted, increase the current to 140-150A.

[0087] After melting, the alloy is further refined and subjected to solution heat treatment in a directional solidification furnace. The directional solidification furnace is heated to 1550℃ and held for refining. After holding at 1550℃ for 30 min, directional solidification is carried out at a uniform drawing speed of 1000 μm / min. The quenching medium is Ga-In-Sn alloy, which gives the alloy a dendritic structure with (0 0 1) orientation.

[0088] The alloy after directional solidification was reloaded into the furnace and heated to the solution heat treatment temperature to dissolve the dendritic structure and the non-uniform precipitates. The solution treatment was carried out at 1250 °C for 5 h. After the solution treatment, it was cooled to the aging heat treatment temperature at 20 °C / min. The aging heat treatment temperature was 900 °C and held for 100 h. Then, it was quenched in Ga-In-Sn at a uniformly accelerated pulling speed of 5000-8000 μm / min.

[0089] Step 2: Alloy microstructure and mechanical property testing

[0090] The microstructure and mechanical properties of the heat-treated alloy were analyzed using SEM, XRD, and a universal tensile testing machine. For XRD testing, diffraction peaks were measured at 10° / min, with a diffraction range of 10-90°. The universal tensile testing machine was used with a compression rate of 0.05 mm / min and a compression deformation of 15%. The as-cast microstructure and XRD patterns of the alloy are attached. Figure 2 , 3 As shown, the microstructure of the as-cast microstructure is as follows: Figure 4 As shown in the figure. The results show that the alloy microstructure of the present invention has a γ / γ′ coherent structure, and the results indicate that the γ′ phase can exist stably at a temperature of 900℃. The microstructure morphology of the alloy is shown in the attached figure. Figure 2 As shown in (c), after aging for 100 h, the size of the γ′ nanoparticles was approximately 210 nm. The room temperature compressive strength was measured to be 842.7 MPa using a universal tensile testing machine. The alloy was subjected to cyclic oxidation in a muffle furnace at 900 ℃. For each sample, the oxidation weight gain was measured by weighing five times and averaging the results to ensure data accuracy. The total oxidation time was 100 h, and the oxidation rate was 5.37 × 10⁻⁶. -8 g 2 / (cm 4 The oxidation weight gain curve is shown in the attached figure. Figure 5 As shown in the attached figure, the XRD pattern of the oxidized surface is as follows. Figure 6 As shown in the attached figure, the microstructure of the oxidized surface is as follows. Figure 7 As shown in (c), the microstructure of the oxide section is as follows. Figure 8 As shown in (c), the bright-field phase and diffraction spots in the transmission electron microscope are as follows: Figure 9 As shown, its coherent structure is illustrated. Example 4

[0091] Co-30Ni-10Al-5V-2Ta-2Ti-12Cr(at%) alloy

[0092] Step 1: Alloy Preparation

[0093] High-purity metal materials were used, and the batches were prepared according to atomic ratios, with a total batch mass of 20 g. The alloy was melted at least five times in a non-consumable vacuum arc melting furnace under an argon atmosphere, with a vacuum level of at least 5 × 10⁻⁶ during evacuation. -4 Pa, during the smelting process, maintain positive pressure inside the furnace. In the early stage of smelting, adjust the current to 120-130A, and after the molten metal is completely melted, increase the current to 140-150A.

[0094] After melting, the alloy is further refined and subjected to solution heat treatment in a directional solidification furnace. The directional solidification furnace is heated to 1550℃ and held for refining. After holding at 1550℃ for 30 min, directional solidification is carried out at a uniform drawing speed of 1000 μm / min. The quenching medium is Ga-In-Sn alloy, which gives the alloy a dendritic structure with (0 0 1) orientation.

[0095] The alloy after directional solidification was reloaded into the furnace and heated to the solution heat treatment temperature to dissolve the dendritic structure and the non-uniform precipitates. The solution treatment was carried out at 1250 °C for 5 h. After the solution treatment, it was cooled to the aging heat treatment temperature at 20 °C / min. The aging heat treatment temperature was 900 °C and held for 100 h. Then, it was quenched in Ga-In-Sn at a uniformly accelerated pulling speed of 5000-8000 μm / min.

[0096] Step 2: Alloy microstructure and mechanical property testing

[0097] The microstructure and mechanical properties of the heat-treated alloy were analyzed using SEM, XRD, and a universal tensile testing machine. For XRD testing, diffraction peaks were measured at 10° / min, with a diffraction range of 10-90°. The universal tensile testing machine was used with a compression rate of 0.05 mm / min and a compression deformation of 15%. The as-cast microstructure and XRD patterns of the alloy are attached. Figure 2 , 3 As shown, the microstructure of the as-cast microstructure is as follows: Figure 4 As shown in the figure; the results show that the alloy microstructure of the present invention has a γ / γ′ coherent structure, and the results indicate that the γ′ phase can exist stably at a temperature of 900 °C. The microstructure morphology of the alloy is shown in the attached figure. Figure 2 As shown in Figure (d), after aging for 100 h, the size of the γ′ nanoparticles was approximately 190 nm. The room temperature compressive strength was measured to be 860.4 MPa using a universal tensile testing machine. The alloy was subjected to cyclic oxidation in a muffle furnace at 900 ℃. For each sample, the oxidation weight gain was measured by weighing five times and averaging the results to ensure data accuracy. The total oxidation time was 100 h. The oxidation weight gain curve is attached. Figure 5 As shown, the oxidation rate is 2.12 × 10⁻⁶. -8 g2 / (cm 4 ·s), XRD pattern of the oxidized surface as shown in the attached figure. Figure 6 As shown in the attached figure, the microstructure of the oxidized surface is as follows. Figure 7 As shown in (d), the microstructure of the oxide cross section is as follows. Figure 8 As shown in (d). Comparative Example 1

[0098] Co-30Ni-10Al-5V-4Ta-2Ti-0Cr(at%) alloy

[0099] Step 1: Alloy Preparation

[0100] High-purity metal materials were used, and the batches were prepared according to atomic ratios, with a total batch mass of 20 g. The alloy was melted at least five times in a non-consumable vacuum arc melting furnace under an argon atmosphere, with a vacuum level of at least 5 × 10⁻⁶ during evacuation. -4 During the melting process, the furnace is kept under positive pressure. The current is adjusted to 120-130A in the initial stage of melting, and increased to 140-150A after the molten metal has completely melted. After melting, the alloy is further refined and subjected to solution heat treatment using a directional solidification furnace. The directional solidification furnace is heated to 1550℃ and held for refining. After holding at 1550℃ for 30 min, directional solidification is performed at a uniform pulling speed of 1000 μm / min. The quenching medium is a Ga-In-Sn alloy, resulting in a (0 0 1) oriented dendritic structure. The directionally solidified alloy is then reloaded into the furnace and heated to the solution heat treatment temperature to dissolve the dendritic structure and uneven precipitates. The solution treatment is performed at 1250℃ for 5 h. After the solution treatment, the alloy is cooled at 20℃ / min to the aging heat treatment temperature of 900℃, held for 100 minutes. After h, it is quenched in Ga-In-Sn at a uniformly accelerated pulling speed of 5000-8000 μm / min.

[0101] Step 2: Alloy microstructure and mechanical property testing

[0102] The microstructure and mechanical properties of the heat-treated alloy were analyzed using SEM, XRD, and a universal tensile testing machine. For XRD testing, diffraction peaks were measured at 10° / min, with a diffraction range of 10-90°. The universal tensile testing machine was used with a compression rate of 0.05 mm / min and a compression deformation of 15%. The as-cast microstructure and XRD patterns of the alloy are attached. Figure 2 , 3 As shown, the microstructure of the as-cast microstructure is as follows: Figure 4As shown in the figure; the results show that the alloy microstructure of the present invention has a γ / γ′ coherent structure, and the results indicate that the γ′ phase can exist stably at a temperature of 900℃. The microstructure morphology of the alloy is shown in the attached figure. Figure 2 As shown in (e), after aging for 100 h, the size of the γ′ nanoparticles was approximately 520 nm. The room temperature compressive strength was measured to be 690.7 MPa using a universal tensile testing machine. The alloy was subjected to cyclic oxidation in a muffle furnace at 900 ℃. For each sample, the oxidation weight gain was measured by weighing five times and taking the average value to ensure data accuracy. The total oxidation time was 100 h, and the oxidation rate was 9.89 × 10⁻⁶. -8 g 2 / (cm 4 The oxidation weight gain curve is shown in the attached figure. Figure 5 As shown in the attached figure, the XRD pattern of the oxidized surface is as follows. Figure 6 As shown in the attached figure, the microstructure of the oxidized surface is as follows. Figure 7 As shown in (e), the microstructure of the oxide cross section is as follows. Figure 8 As shown in (e).

[0103] In summary, the Co-Ni-based superalloy prepared by this invention exhibits a room temperature compressive strength of 629.5–860.4 MPa and an oxidation rate reaching 2.98 × 10⁻⁶ MPa. -8 g 2 / (cm 4 The high-temperature alloy with a particle size of γ' and above (s) has a stable γ / γ′ dual FCC phase structure, with the γ′ phase particle size below 200 nm, exhibiting an ultrafine γ′ phase microstructure, good strength and toughness, low density, and excellent high-temperature oxidation resistance. It can be used in key components in aerospace, petrochemical, nuclear power generation and other fields. This invention provides a method for preparing the high-temperature alloy material, which is simple and conducive to large-scale production.

[0104] The above description is merely a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. For those skilled in the art, improvements and modifications obtained without departing from the inventive concept should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a Co-Ni-based superalloy with a stable γ / γ′ dual FCC phase coherent structure and high-temperature oxidation resistance, characterized in that, include: S1. Alloy melting: The ingredients are batched according to the mass percentage. During the melting process, an inert gas is introduced after vacuuming and a positive pressure is maintained. After the melting is completed, a small current is maintained to help the alloy feed, and a Co-Ni based high-temperature alloy ingot is obtained. S2. Directional solidification treatment: The Co-Ni-based high-temperature alloy ingot obtained in step S1 is loaded into a directional solidification melting furnace, the alloy is heated to above the melting point and then directional solidification treatment is performed to obtain the directional solidified alloy. S3. Graded heat treatment: The alloy obtained in step S2 after directional solidification is put back into the directional solidification melting furnace, heated to the solution temperature and held at that temperature, then slowly cooled to the aging temperature, held at that temperature for a predetermined time and then drawn to obtain the Co-Ni-based high-temperature alloy. In step S2, the alloy is heated to 1500~1600 ℃ and held for 10~60 min. After holding, it is pulled at a constant speed of 500~1000 μm / min. The quenching medium for pulling is Ga-In-Sn alloy, and the mass ratio of Ga-In-Sn alloy is 60~70%, In 10~20%, and Sn 10~20%. In step S3, the temperature is heated to a solution temperature of 1200~1250 ℃, and the solution holding time is 2~10 h. The solution treatment is carried out continuously in a directional solidification furnace to homogenize the alloy. The alloy is then slowly cooled to the aging temperature at a cooling rate of 10~20 ℃ / min. The aging heat treatment temperature is 800~900 ℃, and the holding time is 50~100 h. After the holding time, directional drawing is performed. The aging treatment is a continuous aging treatment to ensure that an aged microstructure is obtained. During the graded heat treatment process, the alloy is subjected to directional cooling treatment and continuous solution aging to ensure uniform alloy microstructure, resulting in a dendritic microstructure with (0 0 1) orientation. The composition of the Co-Ni-based superalloy, by mass percentage, is: Ni 20.0~40.0%, Al 3.0~10.0%, V 2.0~7.0%, Ta 4.0~14.0%, Ti 1.0~5.0%, Cr 5.0~15.0%, with the remainder being Co; The Co-Ni-based superalloy has an FCC+FCC coherent dual-phase structure, in which there is a dispersed Laves phase reinforcement between dendrites; In step S3, the directional pulling process uses uniform acceleration pulling with a pulling speed of 1000~10000 μm / min.

2. The method for preparing a Co-Ni-based superalloy with a stable γ / γ′ dual FCC phase coherent structure and high-temperature oxidation resistance according to claim 1, characterized in that, The composition of the Co-Ni-based superalloy by mass percentage is as follows: Ni 25.0~35.0%, Al 4.0~6.0%, V 3.0~5.0%, Ta 5.0~12.0%, Ti 1.0~3.0%, Cr 5.0~12.0%, with the remainder being Co.

3. The method for preparing a Co-Ni-based superalloy with a stable γ / γ′ dual FCC phase coherent structure and high-temperature oxidation resistance according to claim 1, characterized in that, In step S1, the vacuum level is maintained at 5×10 during the smelting process. -4 Below Pa, after all raw materials have melted, the molten metal is refined to ensure uniform composition. The current during refining is 120~140 A, and the refining time is 1~5 min each time. The remelting is repeated more than 3 times. After refining, a Co-Ni-based high-temperature alloy ingot is obtained.

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