High-strength equiaxed crystal nickel-based superalloy and preparation method thereof

Abstract

The application discloses a high-strength equiaxed crystal nickel-based superalloy and a preparation method thereof, and belongs to the superalloy field. The alloy composition comprises the following components in percentage by mass: 18-20 Co, 19-21.5 Cr, 0.8-2 Nb, 1.9-3.2 Ti, 2-2.2 Al, 0.12-0.14 C, 1.8-3.8 W, 1.7-3.6 Ta, 0.8-2 Mo, and the balance of Ni. The alloy charge is smelted by using a vacuum induction melting furnace, and the alloy has excellent room-temperature tensile properties through solid solution and aging heat treatment. Meanwhile, the alloy has good casting, welding and deformation processing properties, and the technical key lies in reasonable component design, heat treatment and deformation process. The homogenization heat treatment before hot rolling ensures that the alloy does not crack in the hot rolling process, and the recrystallization and aging heat treatment after cold rolling recrystallizes the fiber structure and promotes the uniform precipitation of the second phase, so that the alloy has excellent mechanical properties in a wide temperature range. The component design and the preparation method improve the strength index of the cast and deformed superalloy, and are suitable for being used as parts such as casing and plate structure parts in the aviation and aerospace industries.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature alloy technology and provides a high-strength equiaxed nickel-based high-temperature alloy, which is mainly suitable for manufacturing casings, fasteners and sheet metal structural parts in the aerospace industry. Background Technology

[0002] In modern advanced aero-engines, high-temperature alloys account for 40% to 60% of the total material usage. Nickel-based superalloys exhibit excellent performance at medium to high temperatures. Among them, Inconel 718 alloy (domestic grade K4169 alloy) possesses good fatigue resistance, radiation resistance, oxidation resistance, corrosion resistance, as well as good machinability, weldability, and long-term structural stability. It has become the most widely used nickel-based superalloy in the history of aero-engines. This alloy can withstand service environments with a temperature resistance of 650℃ and is a common material for aero-engine turbines, casings, blades, and other parts. However, although this alloy has good variability, its high-temperature strength is relatively low, making it unsuitable for components with high requirements for high-temperature mechanical properties. On the other hand, cast superalloys such as K465, K438, and K417, which have higher high-temperature performance, have poor deformation capacity and are prone to defects such as cracks during processing, resulting in extremely poor formability. With the continuous development of my country's aviation industry, there is an urgent need for high-strength superalloys with good machinability to further meet the increasingly stringent requirements for aero-engine components. Summary of the Invention

[0003] In view of this, the purpose of this invention is to solve the problems in the prior art and to propose a high-strength equiaxed nickel-based superalloy for aero-engine components and its processing technology. The alloy contains a high content of W, Mo, Nb, Ti and Al, and is microalloyed with C. Through the synergistic effect of second-phase strengthening, solid solution strengthening and grain boundary strengthening, the alloy has excellent high-temperature strength, while being free of rare and precious elements and having low cost.

[0004] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0005] A high-strength equiaxed nickel-based superalloy, characterized in that the superalloy composition by mass percentage (wt.%) is: 18-20Co; 19-21.5Cr; 0.8-2Nb; 1.9-3.2Ti; 2-2.2Al; 0.12-0.14C; 1.8-3.8W; 1.7-3.6Ta; 0.8-2Mo, with Ni as the balance.

[0006] For equiaxed cast superalloys, the main phase composition consists of γ phase (Ni solid solution), γ' phase (Ni3(Al,Ti)), and carbide phases. The γ phase forms the matrix, while both the γ' and carbide phases are strengthening phases. Alloy strengthening mechanisms include second-phase strengthening, solid solution strengthening, and grain boundary strengthening. A proper ratio of alloying elements is crucial for ensuring the alloy's excellent overall performance. Al and Ti are the main strengthening elements of the γ' phase. The high strength of superalloys at high temperatures is primarily due to the precipitation strengthening effect of the γ' phase. However, it is generally believed that a Ti / Al ratio greater than 2 will promote the precipitation of the η phase. In this invention, the Ti / Al ratio is less than 1.6. Solid solution strengthening of cast alloys typically relies on refractory elements such as W, Mo, Nb, and Ta dissolving into the matrix and Ni3(Al,Ti), causing lattice distortion. However, excessively high refractory element content can easily lead to the precipitation of the TCP phase. This invention controls the total amount of W+Mo+Nb+Ta to 5.1%-11.4% to achieve sufficient strengthening of the alloy, avoiding both insufficient solid solution strengthening due to low total amount of refractory elements and precipitation of TCP phase due to excessive refractory element content. Cr is a key element for improving the hot corrosion resistance of alloys. An appropriate amount of Cr must be added to the alloy to ensure its resistance to hot corrosion. In this invention, the Cr content is controlled at 19%-21.5%. Co mainly dissolves in the matrix, reducing the stacking fault energy of the matrix and decreasing the solubility of Al and Ti in the matrix, thereby increasing the number of γ' phases, which is beneficial for improving the creep resistance of the alloy. Simultaneously, Co can increase the solubility of Mo and W in the matrix and inhibit the precipitation of TCP phases. In this invention, the Co content is controlled at 18%-20%. For equiaxed cast superalloys, carbides are also important strengthening phases. C preferentially combines with elements such as Ti and Nb to form the MC phase. The C content directly affects the number of carbides. C is also an important grain boundary strengthening element. Therefore, C is a very important microalloying element for equiaxed cast superalloys. If the C content is too low, the number of carbides is insufficient, resulting in inadequate strengthening. If the C content is too high, the number of carbides is excessive, leading to a decrease in alloy plasticity and consuming a large amount of solid solution strengthening elements, which is detrimental to the strength of the alloy. Therefore, the present invention controls the C content to be between 0.12% and 0.14%.

[0007] A preparation process for a high-strength equiaxed nickel-based superalloy as described above includes the following steps:

[0008] Step 1: Smelting high-temperature alloy ingots in a vacuum induction melting furnace. By mass percentage, use 18-20Co; 19-21.5Cr; 0.8-2Nb; 1.9-3.2Ti; 2-2.2Al; 0.12-0.14C; 1.8-3.8W; 1.7-3.6Ta; 0.8-2Mo, with Ni as the balance. Refine the alloy under vacuum and argon gas protection and then cast it.

[0009] Step two, ingot sampling. Tensile samples are taken from the ingot after machining, and then subjected to solution treatment and aging heat treatment to achieve the purpose of melting back the η phase and eutectic structure and uniformly dispersed precipitation of γ′.

[0010] Step 3, high-temperature hot rolling of the casting. The alloy ingot smelted in Step 1 is subjected to homogenization heat treatment, then cut into 10mm thick plates, and hot rolled at 50-100℃ above the γ′ precipitation temperature, with a final total deformation of not less than 60%.

[0011] Step four, high-temperature solution treatment of the sheet metal. The alloy that has undergone high-temperature rolling in step three is then subjected to high-temperature solution treatment.

[0012] Step 5, cold rolling of the sheet metal. The alloy sheet metal after high-temperature solution treatment in Step 4 is then cold rolled, with the final total deformation not less than 50%.

[0013] Step Six, Recrystallization Treatment. The sheet material after cold rolling in Step Five is subjected to recrystallization treatment to promote the recrystallization of the fiber structure after cold rolling, thereby refining the grain size.

[0014] Step 7, Aging Treatment. The sheet material after cold rolling and recrystallization in Step 6 is subjected to aging treatment to promote the uniform precipitation of γ′ on the matrix.

[0015] Further, in step two, the solution heat treatment specifically involves heating from room temperature to 1160-1180℃ at a heating rate of 10-15℃ / min, holding at that temperature for 4 hours, and then air cooling to room temperature. The aging heat treatment specifically involves heating from room temperature to 830-850℃ at a heating rate of 10-15℃ / min, holding at that temperature for 10-12 hours, and then air cooling to room temperature.

[0016] Furthermore, in step three, the homogenization heat treatment specifically involves heating from room temperature to 1180-1220℃ at a heating rate of 10-15℃ / min, holding at that temperature for 4 hours, and then air cooling to room temperature.

[0017] Furthermore, in step three, hot rolling is carried out at 1170℃. After each rolling pass, the roll is returned to the furnace for heat preservation for a time T≥10min. The hot rolling reduction is 60%.

[0018] Furthermore, in step four, the solution heat treatment specifically involves heating from room temperature to 1150-1180℃ at a heating rate of 10-15℃ / min, holding at that temperature for 4 hours, and then air cooling to room temperature.

[0019] Furthermore, in step six, the recrystallization heat treatment specifically involves heating from room temperature to 1150-1180℃ at a heating rate of 10-15℃ / min, holding at that temperature for 0.5-1h, and then air cooling to room temperature.

[0020] Furthermore, in step seven, the aging heat treatment specifically involves heating from room temperature to 750-800℃ at a heating rate of 10-15℃ / min, holding at that temperature for 10-12 hours, and then air cooling to room temperature.

[0021] The key technical point of this invention is:

[0022] The nickel-based alloy composition involved in the invention patent (CN114032421B) is similar to the alloy range of this application. The difference lies in that the alloy in the invention patent is a nickel-based alloy powder used in additive manufacturing. It utilizes selective laser melting technology to prepare high-temperature alloy parts. Under conditions of rapid solidification with a large temperature gradient, carbides do not have time to grow. The dispersed nanoscale carbides can effectively bear the thermal stress during rapid cooling. Furthermore, due to their large number, the stress dispersed on a single carbide is insufficient to cause cracking. Therefore, the generation of microcracks in the alloy product is suppressed overall, and the high-temperature strength of the alloy product is enhanced. In contrast, the alloy applied for in this invention patent is a nickel-based alloy used in the casting field. After reasonable rolling deformation treatment, the synergistic effect of multiple strengthening gains (solution strengthening, grain refinement strengthening, precipitation strengthening) gives the alloy good mechanical properties over a wide temperature range and good resistance to oxidation and corrosion. In addition, the alloy composition range applied for in this invention patent contains Mo (0.8-2%). In high-temperature alloys, W dissolves in both the γ and γ' phases, each accounting for about half, and has a good solid solution strengthening effect on both. Mo mostly dissolves in the γ matrix, with only about 1 / 4 dissolving in the γ' phase, mainly strengthening the γ matrix. Nb mainly strengthens the γ' phase through solid solution. This invention uses W as the main solid solution strengthening element, and simultaneously uses Mo and Nb for composite alloying to balance the strengthening effect of refractory elements on the γ matrix and the γ' phase.

[0023] Compared with existing technologies, the beneficial effects of this invention are as follows: the alloy of this invention has a higher content of γ′ phase-forming elements, and compared with IN718, the Nb content in the alloy of this invention is lower, which limits the raw material cost of the alloy and also inhibits the precipitation of the γ″ phase. The preparation process abandons the traditional triple melting process of high-temperature alloys and adopts vacuum induction melting followed by rolling, reducing the preparation cost of the alloy. Subsequently, the alloy is subjected to multi-pass large deformation processing, with the rolling temperature controlled within the range of 50-100°C above the γ′ precipitation temperature, ensuring sufficient strain energy storage during alloy processing. Finally, after heat treatment, the alloy exhibits excellent high-temperature strength. Attached Figure Description

[0024] Figure 1 Photographs of ingots used in this embodiment;

[0025] Figure 2 The tensile properties of the example without deformation treatment;

[0026] Figure 3 Examples (after deformation treatment) show tensile properties over a wide temperature range from room temperature (RT) to 750°C;

[0027] Figure 4 This example compares the performance of the alloy after deformation treatment with that of other high-temperature alloys and high-entropy alloys. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0029] Example 1

[0030] The high-strength high-temperature alloy in this embodiment, by mass percentage (wt.%), is: Co: 19.38; Cr: 21.38; Nb: 0.93; Ti: 1.96; Al: 2.14; C: 0.135; W: 1.88; Ta: 1.78; Mo: 0.91, with the balance being Ni.

[0031] The alloy raw materials have a purity of over 99.9%, are melted in an induction arc furnace with argon protection, and then cast to obtain the desired alloy. Figure 1 The ingot shown is used as an example. Tensile specimens are taken from the ingot and heated to 1160℃ at a rate of 10℃ / min, held for 4 hours, and then air-cooled to room temperature. Then, the temperature is increased to 850℃ at a rate of 10℃ / min and held for 10 hours, followed by air cooling to room temperature. This yields the tensile properties of the alloy before deformation, such as... Figure 2 As shown.

[0032] The ingot was heated to 1200℃ at a rate of 10℃ / min and held for 4 hours, then air-cooled to room temperature. 10mm thick alloy plates were cut using wire EDM. The surface oxide scale was polished with a grinding wheel, and the plates were hot-rolled at 100℃ above the γ′ precipitation temperature, with a total deformation of 60%. Each rolling pass was followed by a 10-minute heat treatment in the furnace. After rolling, the alloy was heated to 1160℃ for solution treatment for 4 hours and air-cooled to room temperature. The surface oxide scale was then polished again with a grinding wheel before cold rolling, with a total deformation of 70%. The plates were then heated to 1160℃, held for 1 hour, and air-cooled. Finally, the plates were heated to 750℃, held for 10 hours, and air-cooled. Alloy performance tests showed that at room temperature, the yield strength was 978MPa, the tensile strength was 1481MPa, and the elongation was 21%. At 650℃, the yield strength was 782MPa, the tensile strength was 1072MPa, and the elongation was 13%, indicating that the alloy possesses excellent high-temperature strength properties.

[0033] Example 2

[0034] The high-strength nickel-based superalloy of this embodiment, by mass percentage, is as follows (wt.%): Co: 18.59; Cr: 20.64; Nb: 1.43; Ti: 2.95; Al: 2.07; C: 0.139; W: 2.84; Ta: 2.66; Mo: 1.46, with the balance being Ni.

[0035] The alloy raw materials have a purity of over 99.9%, are melted in an induction arc furnace with argon protection, and then cast to obtain the desired alloy. Figure 1 The ingot shown is used as an example. Tensile specimens are taken from the ingot and heated to 1160℃ at a rate of 10℃ / min, held for 4 hours, and then air-cooled to room temperature. Then, the temperature is increased to 850℃ at a rate of 10℃ / min and held for 10 hours, followed by air cooling to room temperature. This yields the tensile properties of the alloy before deformation, such as... Figure 2 As shown.

[0036] After casting, the ingot is heated to 1200℃ at a rate of 10℃ / min and held for 4 hours, then air-cooled to room temperature. 10mm thick alloy plates are cut using wire EDM. The surface oxide scale is polished with a grinding wheel and then hot-rolled at 50℃ above the γ′ precipitation temperature, with a total deformation of 60%. After each rolling pass, the plate is reheated and held in the furnace for 10 minutes. After alloy rolling, the plate is heated to 1160℃ for solution treatment for 4 hours and then air-cooled to room temperature. The surface oxide scale is then polished again with a grinding wheel and cold-rolled, with a total deformation of 70%. The plate is then heated to 1160℃, held for 1 hour, and air-cooled. Finally, the plate is heated to 750℃, held for 10 hours, and then air-cooled.

[0037] The alloy performance test results show that its yield strength at room temperature is 1129 MPa, tensile strength is 1563 MPa, and elongation is 14.8%. At 650℃, its yield strength is 1018 MPa and tensile strength is 1265 MPa, which are better than those of IN718 alloy, indicating that the alloy has excellent high-temperature strength performance.

[0038] Example 3

[0039] The high-strength nickel-based superalloy of this embodiment comprises, by mass percentage: Co: 18.10; Cr: 19.94; Nb: 1.87; Ti: 3.09; Al: 2.01; C: 0.14; W: 3.8; Ta: 3.54; Mo: 1.99, with the balance being Ni.

[0040] The alloy raw materials have a purity of over 99.9%, are melted in an induction arc furnace with argon protection, and then cast to obtain the desired alloy. Figure 1The ingot shown is used as an example. Tensile specimens are taken from the ingot and heated to 1160℃ at a rate of 10℃ / min, held for 4 hours, and then air-cooled to room temperature. Then, the temperature is increased to 850℃ at a rate of 10℃ / min and held for 10 hours, followed by air cooling to room temperature. This yields the tensile properties of the alloy before deformation, such as... Figure 2 As shown, the yield strength reaches 887 MPa and the tensile strength reaches 1133 MPa, which is better than IN939 alloy (yield strength is 862 MPa and tensile strength is 1087 MPa).

[0041] After casting, the ingot is heated to 1200℃ at a rate of 10℃ / min and held for 4 hours, then air-cooled to room temperature. A 10mm thick alloy sheet is cut using a wire EDM machine. The surface oxide scale is polished with a grinding wheel and then hot-rolled at 60℃ above the γ′ precipitation temperature, with a total deformation of 60%. After each rolling pass, the sheet is reheated and held in the furnace for 10 minutes. After alloy rolling, the temperature is raised to 1160℃ for solution treatment for 4 hours and air-cooled to room temperature. The surface oxide scale is then polished again with a grinding wheel and cold-rolled, with a total deformation of 57%. The sheet is then heated to 1160℃, held for 1 hour, and air-cooled. Finally, the sheet is heated to 750℃, held for 10 hours, and then air-cooled.

[0042] The alloy performance test results show that its yield strength at room temperature is 1167 MPa, tensile strength is 1632 MPa, and elongation is 14.6%. At 650℃, its yield strength is 1088 MPa and tensile strength is 1382 MPa, which are far superior to IN718 alloy, indicating that the alloy has excellent high-temperature strength performance.

Claims

1. A high-strength equiaxed nickel-based superalloy, characterized in that... The high-temperature alloy composition by mass percentage (wt.%) is: 18-20 Co; 19-21.5 Cr; 0.8-2 Nb; 1.9-3.2 Ti; 2-2.2 Al; 0.12-0.14 C; 1.8-3.8 W; 1.7-3.6 Ta; 0.8-2 Mo, with a Ti / Al ratio below 1.

6. The total amount of W+Mo+Nb+Ta is controlled at 5.1%-11.4%, with the balance being Ni and unavoidable trace impurity elements. The preparation process of the high-strength equiaxed nickel-based superalloy includes the following steps: Step 1: Smelting high-temperature alloy ingots in a vacuum induction melting furnace: By mass percentage, take 18-20 Co; 19-21.5 Cr; 0.8-2 Nb; 1.9-3.2 Ti; 2-2.2 Al; 0.12-0.14 C; 1.8-3.8 W; 1.7-3.6 Ta; 0.8-2 Mo, with Ni as the balance; refine the alloy under vacuum and argon gas protection and then cast it. Step 2, ingot sampling: Tensile samples are taken from the ingot after machining, and then subjected to solution treatment and aging heat treatment to achieve the purpose of melting back the η phase and eutectic structure and uniformly dispersed precipitation of γ′. Step 3, High-temperature hot rolling of the casting: The alloy ingot smelted in Step 1 is subjected to homogenization heat treatment, then cut into 10mm thick plates, and hot rolled at 50-100℃ above the γ′ precipitation temperature, with the final total deformation not less than 60%; Step 4, High-temperature solution treatment of the sheet metal: The alloy that has been rolled at high temperature in Step 3 is subjected to high-temperature solution treatment. Step 5, Cold rolling of sheet metal: The alloy sheet metal after high-temperature solution treatment in Step 4 is cold rolled, and the final total deformation is not less than 50%. Step 6, recrystallization treatment: The sheet material after cold rolling in step 5 is subjected to recrystallization treatment to promote the recrystallization of the fiber structure after cold rolling, thereby refining the grain size. Step 7, Aging Treatment: The sheet material after cold rolling and recrystallization in Step 6 is subjected to aging treatment to promote the uniform precipitation of γ′ on the matrix.

2. The preparation process of the high-strength equiaxed nickel-based superalloy according to claim 1, characterized in that, Includes the following steps: Step 1: Smelting high-temperature alloy ingots in a vacuum induction melting furnace: By mass percentage, take 18-20 Co; 19-21.5 Cr; 0.8-2 Nb; 1.9-3.2 Ti; 2-2.2 Al; 0.12-0.14 C; 1.8-3.8 W; 1.7-3.6 Ta; 0.8-2 Mo, with Ni as the balance; refine the alloy under vacuum and argon gas protection and then cast it. Step 2, ingot sampling: Tensile samples are taken from the ingot after machining, and then subjected to solution treatment and aging heat treatment to achieve the purpose of melting back the η phase and eutectic structure and uniformly dispersed precipitation of γ′. Step 3, High-temperature hot rolling of the casting: The alloy ingot smelted in Step 1 is subjected to homogenization heat treatment, then cut into 10mm thick plates, and hot rolled at 50-100℃ above the γ′ precipitation temperature, with the final total deformation not less than 60%; Step 4, High-temperature solution treatment of the sheet metal: The alloy that has been rolled at high temperature in Step 3 is subjected to high-temperature solution treatment. Step 5, Cold rolling of sheet metal: The alloy sheet metal after high-temperature solution treatment in Step 4 is cold rolled, and the final total deformation is not less than 50%. Step 6, recrystallization treatment: The sheet material after cold rolling in step 5 is subjected to recrystallization treatment to promote the recrystallization of the fiber structure after cold rolling, thereby refining the grain size. Step 7, Aging Treatment: The sheet material after cold rolling and recrystallization in Step 6 is subjected to aging treatment to promote the uniform precipitation of γ′ on the matrix.

3. The preparation process of a high-strength equiaxed nickel-based superalloy according to claim 2, characterized in that, In step two, the solution heat treatment is specifically as follows: the temperature is increased from room temperature to 1160-1180℃ at a heating rate of 10-15℃ / min, held for 4 hours, and then air-cooled to room temperature; the aging heat treatment is specifically as follows: the temperature is increased from room temperature to 830-850℃ at a heating rate of 10-15℃ / min, held for 10-12 hours, and then air-cooled to room temperature.

4. The preparation process of a high-strength equiaxed nickel-based superalloy according to claim 2, characterized in that, In step three, the homogenization heat treatment specifically involves heating from room temperature to 1180-1220℃ at a heating rate of 10-15℃ / min, holding at that temperature for 4 hours, and then air cooling to room temperature.

5. The preparation process of a high-strength equiaxed nickel-based superalloy according to claim 2, characterized in that, In step three, hot rolling is carried out at 1170℃. After each rolling pass, the product is returned to the furnace for heat preservation for a time T ≥ 10 min.

6. The preparation process of a high-strength equiaxed nickel-based superalloy according to claim 2, characterized in that, In step four, the solution heat treatment specifically involves heating from room temperature to 1150-1180℃ at a heating rate of 10-15℃ / min, holding at that temperature for 4 hours, and then air cooling to room temperature.

7. The preparation process of a high-strength equiaxed nickel-based superalloy according to claim 2, characterized in that, In step six, the recrystallization heat treatment specifically involves heating from room temperature to 1150-1180℃ at a heating rate of 10-15℃ / min, holding at that temperature for 0.5-1h, and then air cooling to room temperature.

8. The preparation process of a high-strength equiaxed nickel-based wrought superalloy according to claim 2, characterized in that, In step seven, the aging heat treatment specifically involves heating from room temperature to 750-800℃ at a heating rate of 10-15℃ / min, holding at that temperature for 10-12 hours, and then air cooling to room temperature.

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