A heat treatment method for high-performance nickel-based superalloys

Abstract

This invention provides a heat treatment method for high-performance nickel-based superalloys. In this heat treatment method, the cooling rate of the alloy after solution treatment is between that of air cooling and oil cooling; in the two-stage continuous aging treatment, furnace cooling is used after the first stage of aging, and air cooling is used after the second stage of aging. After aging, while obtaining finely dispersed secondary γ′ phases, the γ′ phase aggregates at the grain boundaries, which strengthens the grain boundaries and improves the plasticity of the alloy. Compared with standard heat treatment processes, this method is simple and efficient, and has unexpected effects on improving the room temperature and high temperature strength of the alloy. The room temperature tensile strength reaches 1504 MPa, and the yield strength reaches 1076 MPa, with the maximum improvement reaching 75 MPa and 149 MPa, respectively; the 650℃ tensile strength reaches 1359 MPa, and the yield strength reaches 1007 MPa, with the maximum improvement reaching 77 MPa and 121 MPa, respectively.

Description

Technical Field

[0001] This application relates to the technical field of heat treatment of nickel-based superalloys, and in particular to a high-performance heat treatment method for nickel-based superalloys. Background Technology

[0002] Powder metallurgy superalloys are high-temperature materials prepared using powder metallurgy processes that can resist oxidation or corrosion at temperatures of 650℃ and above, and can operate for extended periods under certain stress. Compared with traditional cast and forged superalloys, they have advantages such as uniform microstructure, no macroscopic segregation, high yield strength, and good fatigue performance, making them the preferred materials for key hot-end components such as high-pressure turbine disks in advanced aero-engines.

[0003] Heat treatment of powder metallurgy superalloys includes solution treatment and aging treatment. Solution treatment aims to dissolve carbides and γ' phases in the matrix to obtain a uniform austenitic solid solution, facilitating the uniform precipitation of the γ' phase during subsequent quenching and cooling. Additionally, solution treatment can achieve a suitable grain size, improving the alloy's strength or high-temperature creep resistance. Aging treatment aims to ensure the precipitation of more fine γ' phases, while simultaneously promoting a more rational distribution of carbides and a more stable microstructure, thereby further enhancing the alloy's properties.

[0004] Currently, the commonly used heat treatment regime for this alloy is solution treatment followed by single-stage aging heat treatment. After solution treatment, the alloy is slowly cooled to the γ+γ′ two-phase region and then air-cooled, followed by a long-term high-temperature aging treatment to increase the size of the strengthening γ′ phase and ultimately improve the alloy's plasticity. However, this heat treatment method is time-consuming and cumbersome, and the alloy strength is relatively low. With increasingly higher requirements for the tensile strength, creep strength, and low-cycle fatigue performance of this alloy, it is necessary to develop a simple and efficient heat treatment regime suitable for this nickel-based superalloy. Summary of the Invention

[0005] This application provides a high-performance heat treatment method for nickel-based superalloys. The aim is to successfully enhance the alloy's strength by utilizing a rapid cooling rate following solution treatment, combined with a continuous two-stage aging process. This also improves the efficiency of the heat treatment process, facilitating continuous production. The method is simple and efficient, while ensuring the alloy's low-cycle fatigue performance and operational safety. It is suitable for components requiring high strength from nickel-based superalloys.

[0006] In a first aspect, a method for heat-treating high-performance nickel-based superalloys is provided, characterized by comprising:

[0007] Nickel-based high-temperature alloy pre-alloyed powder is packed into a stainless steel sleeve, and then vacuum degassed and sealed to obtain the sealed alloy powder.

[0008] The sealed alloy powder is hot isostatically pressed to obtain a cylindrical ingot.

[0009] Remove the stainless steel cladding from the outer surface of the cylindrical ingot to obtain a nickel-based superalloy;

[0010] Nickel-based superalloys are solution treated at 1200-1220℃ for 2-4 hours, then removed and cooled to room temperature by strong air blowing.

[0011] After solution treatment, the nickel-based superalloy is aged at 930-960℃ for 5-9 hours, then cooled in the furnace to 760-790℃ for 8-16 hours, and then taken out and air-cooled to room temperature.

[0012] In conjunction with the first aspect, in some implementations of the first aspect, the particle size range of the nickel-based high-temperature alloy pre-alloyed powder is 45 to 150 μm, and the equipment used for loading the powder is a vacuum glove box, which is filled with high-purity argon gas of 99.99% or higher.

[0013] In conjunction with the first aspect, in some implementations of the first aspect, the hot isostatic pressing process parameters are a two-step hot isostatic pressing method, including: first holding at a temperature of 1030-1050℃ and a pressure of 120-140MPa, and then raising the temperature and pressure to a temperature of 1210-1230℃ and a pressure of 140-160MPa and holding at that temperature.

[0014] In conjunction with the first aspect, in some implementations of the first aspect, the heating rate of the solution treatment is 5-10℃ / min.

[0015] In conjunction with the first aspect, in some implementations of the first aspect, the heating rate of the first stage aging treatment after solution treatment is 5-10℃ / min.

[0016] In conjunction with the first aspect, in some implementations of the first aspect, the cooling rate of the strong air blowing to room temperature is controlled in the range of 80-200℃ / min.

[0017] In conjunction with the first aspect, in some implementations of the first aspect, the cooling rate of the furnace during the aging process is controlled within the range of 30-60℃ / h.

[0018] In conjunction with the first aspect, in certain implementations of the first aspect, the nickel-based superalloy, in addition to nickel as the main component, comprises the following other main components by mass percentage: carbon 0.02-0.08%, chromium 5-12%, cobalt 10-18%, molybdenum 1-5%, tungsten 4-7%, aluminum 3-6%, titanium 1-3%, niobium 1-3%, and hafnium 0.01-0.5%.

[0019] In conjunction with the first aspect, in some implementations of the first aspect, the nickel-based superalloy is an FGH4097 alloy or an EP741NP alloy.

[0020] In conjunction with the first aspect, in certain implementations of the first aspect, the main components of the nickel-based superalloy, by mass percentage, are: carbon 0.03-0.06%, chromium 8-10%, cobalt 15-16.5%, molybdenum 3.5-4.2%, tungsten 5.2-5.9%, aluminum 4.8-5.3%, titanium 1.6-2.0%, niobium 2.4-2.8%, hafnium 0.1-0.4%, silicon ≤0.5%, sulfur ≤0.009%, phosphorus ≤0.015%, oxygen ≤0.007%, iron ≤0.5%, manganese ≤0.5%, magnesium ≤0.02%, boron ≤0.015%, zirconium ≤0.015%, cerium ≤0.01%, with the balance being nickel.

[0021] Compared with the prior art, the solution provided in this application has at least the following beneficial technical effects:

[0022] 1. This invention discloses a heat treatment method for improving the strength of nickel-based superalloys. After solution treatment, a strong air cooling method is used to control the cooling rate in the range of 80-200℃ / min. This cooling rate is between that of oil cooling and air cooling, which will significantly increase the number of γ′ phase nuclei and inhibit the rapid growth of the γ′ phase.

[0023] 2. The subsequent aging stage employs a continuous two-stage aging treatment. The first stage is a high-temperature aging treatment, during which the γ′ strengthening phase precipitates and a small amount of dispersed γ′ phase agglomerates, increasing the stability of the γ′ phase. Simultaneously, fine M6C carbides precipitate at the grain boundaries, along with a small amount of MC, further strengthening the grain boundaries. During furnace cooling, M6C further precipitates and grows, promoting the formation of bent grain boundaries and effectively improving the alloy's plasticity. The second stage is a low-temperature aging treatment, during which finer γ′ phases are further precipitated, effectively ensuring the precipitation strengthening effect.

[0024] 3. The heat treatment method of this invention, combined with inert gas powder loading and a two-step hot isostatic pressing process, has unexpected effects on improving the strength of the alloy.

[0025] 4. This heat treatment method is simple to operate, can effectively reduce the traditional heat treatment time, and thus save energy, making it highly valuable for promotion. Attached Figure Description

[0026] Figure 1 This is a distribution diagram of the γ′ phase in the alloy after solid solution treatment and two-stage aging in Example 1.

[0027] Figure 2 This is a distribution diagram of the γ′ phase in the alloy after heat treatment. Detailed Implementation

[0028] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0029] This application provides a heat treatment method for high-performance nickel-based superalloys, which specifically includes the following steps.

[0030] Step 1: The high-temperature alloy pre-alloyed powder is loaded into a stainless steel sleeve, and vacuum degassing and sealing are performed to obtain the sealed alloy powder.

[0031] Step 2: The sealed alloy powder is hot isostatically pressed to obtain a cylindrical ingot.

[0032] Step 3: Remove the stainless steel cladding from the outer surface of the cylindrical ingot to obtain the high-temperature alloy.

[0033] Step 4: The high-temperature alloy is solution treated at 1200-1220℃ for 2-4 hours, then removed and cooled to room temperature by strong air blowing.

[0034] Step 5: The alloy is aged at 930-960℃ for 5-9 hours, then cooled in the furnace to 760-790℃ for 8-16 hours, and then removed and air-cooled to room temperature.

[0035] Furthermore, in step 1, the particle size range of the high-temperature alloy pre-alloyed powder is 45–150 μm, and the equipment used for powder loading is a vacuum glove box, which is filled with high-purity argon gas of 99.99% or higher.

[0036] Furthermore, the hot isostatic pressing process parameters in step 2 are a two-step hot isostatic pressing method, that is, first holding at 1030-1050℃ and 120-140MPa pressure for 1 hour, and then raising the temperature and pressure to 1210-1230℃ and holding at 140-160MPa pressure for 1 hour.

[0037] Furthermore, the heating rate described in steps 4 and 5 is 5-10℃ / min.

[0038] Furthermore, the cooling rate during cooling in step 4 is controlled within the range of 80-200℃ / min.

[0039] Furthermore, in step 5, the furnace cooling rate is controlled within the range of 30-60℃ / h.

[0040] Furthermore, in addition to nickel as the main component, the other main components of the nickel-based superalloy are, by mass percentage: carbon 0.02-0.08%, chromium 5-12%, cobalt 10-18%, molybdenum 1-5%, tungsten 4-7%, aluminum 3-6%, titanium 1-3%, niobium 1-3%, and hafnium 0.01-0.5%.

[0041] Furthermore, the nickel-based superalloy is either FGH4097 alloy or EP741NP alloy.

[0042] Further, by mass percentage, the main components of the nickel-based superalloy are: carbon 0.03-0.06%, chromium 8-10%, cobalt 15-16.5%, molybdenum 3.5-4.2%, tungsten 5.2-5.9%, aluminum 4.8-5.3%, titanium 1.6-2.0%, niobium 2.4-2.8%, hafnium 0.1-0.4%, silicon ≤0.5%, sulfur ≤0.009%, phosphorus ≤0.015%, oxygen ≤0.007%, iron ≤0.5%, manganese ≤0.5%, magnesium ≤0.02%, boron ≤0.015%, zirconium ≤0.015%, cerium ≤0.01%, with the balance being nickel.

[0043] FGH4097 alloy is a high-strength powder metallurgy alloy developed in my country in recent years. This alloy possesses excellent comprehensive mechanical properties and a long-term operating temperature of 650–750℃. In my country, FGH4097 alloy is mainly used to manufacture various components such as turbine disks, compressor disks, and drum shafts for aerospace engines under development or already in service.

[0044] The high-temperature alloy pre-alloying powder mentioned in the examples is specifically the same batch of raw material FGH4097 alloy or EP741NP alloy, and the specific composition is shown in Table 1.

[0045] Table 1. Composition of high-temperature alloy pre-alloying powder used in the examples.

[0046] Content (wt.%) 0.042 9.12 3.94 5.62 5.07 1.86 15.83 Element Nb Hf Ce Zr B Mg Si Content (wt.%) 2.58 0.22 <0.01 <0.01 0.014 <0.01 0.028 Element Mn Fe S P O Ni Content (wt.%) <0.01 0.064 <0.002 <0.005 0.0036 margin

[0047] This application provides a heat treatment method for high-performance nickel-based superalloys, including the following steps:

[0048] Step 1: In a vacuum glove box filled with high-purity argon gas of 99.99% or higher, 45-150μm high-temperature alloy pre-alloy powder is placed into a stainless steel sleeve, and vacuum degassing and sealing are performed to obtain the sealed alloy powder.

[0049] Step 2: The alloy powder after sealing is first held at 1030-1050℃ and 120-140MPa for 1 hour, and then the temperature and pressure are increased to 1210-1230℃ and 140-160MPa for 1 hour to obtain a cylindrical ingot.

[0050] Step 3: Remove the stainless steel cladding from the outer surface of the cylindrical ingot to obtain the high-temperature alloy;

[0051] Step 4: Heat the high-temperature alloy to 1200-1230℃ at a rate of 5-10℃ / min for solution treatment for 2-4 hours, and then cool it to room temperature by blowing strong air at a rate of 80-200℃ / min.

[0052] Step 5: Heat the high-temperature alloy to 930-960℃ at a rate of 5-10℃ / min for aging treatment for 5-9 hours, then cool it in the furnace at a rate of 30-60℃ / h to 760-790℃ for aging treatment for 8-16 hours, and then remove it and air cool it to room temperature. Specific Implementation Example 1

[0054] Step 1: In a vacuum glove box filled with high-purity argon gas of 99.99% or higher, 45-150μm high-temperature alloy pre-alloy powder is placed into a stainless steel sleeve, and vacuum degassing and sealing are performed to obtain the sealed alloy powder.

[0055] Step 2: The alloy powder after sealing is first held at 1030℃ and 120MPa for 1 hour, and then the temperature and pressure are increased to 1210℃ and 140MPa for 1 hour to obtain a cylindrical ingot.

[0056] Step 3: Remove the stainless steel cladding from the outer surface of the cylindrical ingot to obtain the high-temperature alloy;

[0057] Step 4: The high-temperature alloy is heated to 1210℃ at a rate of 8℃ / min for solution treatment for 3 hours. After being taken out, it is cooled to room temperature by blowing strong air at a rate of 80-200℃ / min.

[0058] Step 5: The high-temperature alloy is heated to 930℃ at a rate of 8℃ / min and aged for 7 hours. Then it is cooled in the furnace at a rate of 50℃ / h to 770℃ and aged for 10 hours. Finally, it is taken out and air-cooled to room temperature. Specific Implementation Example 2

[0060] Step 1: In a vacuum glove box filled with high-purity argon gas of 99.99% or higher, 45-150μm high-temperature alloy pre-alloy powder is placed into a stainless steel sleeve, and vacuum degassing and sealing are performed to obtain the sealed alloy powder.

[0061] Step 2: The alloy powder after sealing is first held at 1050℃ and 140MPa for 1 hour, and then the temperature and pressure are increased to 1220℃ and 160MPa for 1 hour to obtain a cylindrical ingot.

[0062] Step 3: Remove the stainless steel cladding from the outer surface of the cylindrical ingot to obtain the high-temperature alloy;

[0063] Step 4: The high-temperature alloy is heated to 1220℃ at a rate of 6℃ / min for solution treatment for 2 hours. After being taken out, it is cooled to room temperature by blowing strong air at a rate of 80-200℃ / min.

[0064] Step 5: The high-temperature alloy is heated to 950℃ at a rate of 6℃ / min and aged for 8 hours. Then it is cooled in the furnace at a rate of 60℃ / h to 760℃ and aged for 12 hours. Finally, it is taken out and air-cooled to room temperature.

[0065] Figure 1 This is a distribution diagram of the γ′ phase in the alloy after solid solution treatment and two-stage aging in Example 1. Figure 2 This is a distribution diagram of the γ′ phase in the alloy after existing heat treatment. Mechanical property tests on multiple sets of furnace-fed samples show that the strength values ​​of FGH4097 alloy or EP741NP alloy treated with the heat treatment method described in this invention are significantly improved at both room temperature and high temperature. Specifically, the room temperature tensile strength reaches 1504 MPa, and the yield strength reaches 1076 MPa, with maximum increases of 75 MPa and 149 MPa, respectively; the 650℃ tensile strength reaches 1359 MPa, and the yield strength reaches 1007 MPa, with maximum increases of 77 MPa and 121 MPa, respectively.

[0066] The mechanical properties tested using in-furnace samples are shown in Table 2.

[0067] Table 2. Test results of mechanical properties of FGH4097 alloy or EP741NP alloy

[0068]

[0069] In summary, this invention provides a heat treatment method for nickel-based high-temperature alloys. By optimizing the heat treatment process and the alloy microstructure, the room temperature and high temperature tensile strength and yield strength of the alloy are significantly improved compared with existing processes.

[0070] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims of the present invention.

Claims

1. A heat treatment method for high-performance nickel-based superalloys, characterized in that, include: Nickel-based high-temperature alloy pre-alloyed powder is packed into a stainless steel sleeve, and then vacuum degassed and sealed to obtain the sealed alloy powder. The sealed alloy powder is hot isostatically pressed to obtain a cylindrical ingot. Remove the stainless steel cladding from the outer surface of the cylindrical ingot to obtain a nickel-based superalloy; Nickel-based superalloys are solution treated at 1200-1220℃ for 2-4 hours, then removed and cooled to room temperature by strong air blowing. After solution treatment, the nickel-based superalloy is aged at 930-960℃ for 5-9 hours, then cooled in the furnace to 760-790℃ for 8-16 hours, and then taken out and air-cooled to room temperature. The nickel-based high-temperature alloy pre-alloyed powder has a particle size range of 45~150μm, and the equipment used for loading the powder is a vacuum glove box, which is filled with high-purity argon gas of 99.99% or higher. The main components of the nickel-based superalloy, by mass percentage, are: carbon 0.03-0.06%, chromium 8-10%, cobalt 15-16.5%, molybdenum 3.5-4.2%, tungsten 5.2-5.9%, aluminum 4.8-5.3%, titanium 1.6-2.0%, niobium 2.4-2.8%, hafnium 0.1-0.4%, silicon ≤0.5%, sulfur ≤0.009%, phosphorus ≤0.015%, oxygen ≤0.007%, iron ≤0.5%, manganese ≤0.5%, magnesium ≤0.02%, boron ≤0.015%, zirconium ≤0.015%, cerium ≤0.01%, with the balance being nickel; The hot isostatic pressing process parameters are a two-step hot isostatic pressing method, including: first holding at a temperature of 1030-1050℃ and a pressure of 120-140MPa, and then raising the temperature and pressure to a temperature of 1210-1230℃ and a pressure of 140-160MPa and holding at that temperature. The cooling rate of the strong air cooling to room temperature is controlled within the range of 80-200℃ / min; The cooling rate during the aging process is controlled within the range of 30-60℃ / h.

2. The method according to claim 1, characterized in that, The heating rate for solution treatment is 5-10℃ / min.

3. The method according to claim 1, characterized in that, The heating rate for the first stage of aging treatment after solution treatment is 5-10℃ / min.

Images