A crack-resistant nickel-based superalloy, its preparation method, and its application.

Abstract

This invention discloses a crack-resistant nickel-based superalloy, its preparation method, and its applications, belonging to the field of nickel-based alloy technology. The crack-resistant nickel-based superalloy, by mass percentage, comprises: Cr: 12-18%; Co: 8-15%; Mo: 3-6%; W: 2-4%; Al: 1-3%; Ti: 2-4%; Ru: 0.5-2%; Y: 0.3-1%; B: 0.002-0.01%; with the balance being Ni and unavoidable impurities. This invention utilizes rare earth oxides to passivate aluminum, forming a Y₂O₃ passivation layer, effectively suppressing the precipitation of low-melting-point phases and significantly reducing the crack propagation rate under high-temperature cyclic loading. Simultaneously, it optimizes grain boundary bonding energy, improving the long-term service stability of the alloy under oxidative-thermal corrosion coupled environments. Through the Ni-B master alloy preparation process, using carbothermic reduction and liquid filtration technology, boron segregation and the formation of brittle borides are avoided, eliminating grain boundary stress concentration sources and ensuring uniform boron distribution in the matrix. This suppresses intergranular fracture tendency under high-temperature and high-stress conditions, extending the alloy's lifespan.

Description

Technical Field

[0001] This invention relates to the field of nickel-based alloys, and more particularly to a crack-resistant nickel-based superalloy, its preparation method, and its applications. Background Technology

[0002] Nickel-based superalloys, as core materials for hot-end components of aero-engines and gas turbines, must maintain excellent microstructural stability, fatigue resistance, and corrosion resistance under high-temperature environments (950-1050℃) and complex stress conditions. However, during long-term high-temperature service, the fatigue strength, yield strength, and creep resistance of the alloys will significantly decrease, with grain boundary cracking being one of the main failure modes.

[0003] When conventional aluminum powder is added, the Al2O3 passivation layer formed on the surface has low density. During high-temperature melting, oxygen diffusion and penetration lead to the precipitation of low-melting-point phases at the grain boundaries, which significantly weakens the grain boundary bonding energy. As a result, when the alloy is in long-term service in an oxidation-thermal corrosion coupled environment (such as the combustion chamber of an aero-engine), the crack propagation rate under high-temperature cyclic load increases sharply, which seriously restricts the service life of the components.

[0004] When boron powder is added directly, its low density makes it prone to floating and agglomeration. Surface B2O3 impurities react with matrix elements to form a brittle eutectic phase with a melting point below 900℃, which then segregates at grain boundaries to form coarse borides, becoming stress concentration sources. Under high temperature and high stress conditions, cracks propagate rapidly along the brittle borides, initiating intergranular fracture and leading to premature component failure.

[0005] Therefore, those skilled in the art are dedicated to developing a crack-resistant nickel-based superalloy, its preparation method, and its applications to solve the above-mentioned problems. Summary of the Invention

[0006] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is to improve the crack resistance of nickel-based superalloys.

[0007] To achieve the above objectives, the present invention provides a crack-resistant nickel-based superalloy, comprising the following components by mass percentage: Cr: 12-18%; Co: 8-15%; Mo: 3-6%; W: 2-4%; Al: 1-3%; Ti: 2-4%; Ru: 0.5-2%; Y: 0.3-1%; B: 0.002-0.01%; with the balance being Ni and unavoidable impurities.

[0008] Al is passivated with Y2O3; B exists in the form of a Ni-B master alloy.

[0009] A method for preparing the aforementioned crack-resistant nickel-based superalloy includes the following steps:

[0010] S1. Pretreatment of aluminum;

[0011] Aluminum powder and yttrium oxide powder are mixed, sintered under argon protection, and then ground to obtain passivated aluminum powder;

[0012] S2. Preparation of Ni-B master alloy;

[0013] Nickel oxide powder was immersed in a boron-containing solution and stirred, then oxidized and dried in high-temperature air to obtain pre-coated nickel oxide powder.

[0014] Boric anhydride powder and pre-coated nickel oxide powder were vacuum dried, sieved and mixed, polyvinyl alcohol binder was added, cold isostatic pressing was performed, and then heated under argon protection to generate liquid Ni(BO2)2.

[0015] Liquid Ni(BO2)2 is pre-reduced with carbon powder at 1350℃ for 30 min, and then reacted at a constant temperature of 1550-1600℃ to generate NiB; it is then slowly cooled to 1200-1300℃ and kept at that temperature, and impurities are filtered out.

[0016] NiB master alloy was obtained by casting and NiB master alloy powder was obtained by grinding.

[0017] S3. Vacuum induction melting and degassing treatment;

[0018] The dried nickel, chromium, cobalt, molybdenum, tungsten, titanium, and ruthenium powders are added to a vacuum induction furnace, evacuated to a vacuum, heated to 1950-2000℃, and then cooled to 1550-1600℃ for constant-temperature melting; high-purity argon is then introduced for degassing.

[0019] After cooling to 1450-1500℃, add passivated aluminum powder; add Ni-B master alloy powder in batches.

[0020] The temperature is lowered to 1400-1450℃, and the furnace is tilted to pour the ingot into a water-cooled copper mold to obtain an ingot.

[0021] S4. Pulse electroslag remelting;

[0022] An electroslag remelting furnace is used to load preheated and dehydrated ternary slag system CaF2-Al2O3-CaO into the crystallizer; before melting, the furnace body is evacuated and high-purity argon gas is introduced, and the crystallizer cooling water system is started simultaneously; the ingot is put into the molten pool and intermittently pulsed.

[0023] S5. Forging of blanks;

[0024] The ingot is heated to 1150-1200℃ using a high-speed forging mill and held at that temperature. A multi-directional forging process with alternating axial and radial deformation is then employed, followed by air cooling to room temperature.

[0025] S6. Cold rolled and cold drawn;

[0026] The billet is annealed immediately after cold rolling, and a high-temperature resistant lubricant is evenly sprayed onto the surface of the billet. After the lubricant layer has solidified, it is cold-drawn to obtain the finished product; it is then polished in an electrolyte solution.

[0027] S7. Heat treatment annealing;

[0028] After solution treatment, high-pressure nitrogen gas at 1.2 MPa is introduced and the temperature is rapidly cooled to 300°C at a rate of 50-100°C / min; aging treatment is then performed, followed by furnace cooling and air cooling to obtain a crack-resistant nickel-based superalloy.

[0029] In a preferred embodiment of the present invention, S1 specifically involves: mixing aluminum powder with yttrium oxide powder, sintering at 380-400°C for 1-2 hours under argon protection, and grinding the mixture into passivated aluminum powder with a particle size ≤50μm.

[0030] In another preferred embodiment of the present invention, S2 specifically involves: immersing nickel oxide powder completely in a boron-containing solution and stirring, then oxidizing and drying it in high-temperature air to generate a Ni-BO coating layer on the surface, thereby obtaining pre-coated nickel oxide powder.

[0031] Boric anhydride powder and pre-coated nickel oxide powder were vacuum dried to remove adsorbed water and sieved to a particle size ≤50μm.

[0032] B2O3 and NiO are mixed in a molar ratio of 1:1-1.2, polyvinyl alcohol binder is added, and the mixture is cold isostatically pressed into cylindrical blocks. The blocks are then heated to 950-1000℃ under argon protection and held for 1-1.5 hours to produce liquid Ni(BO2)2.

[0033] Liquid Ni(BO2)2 and carbon powder are loaded into a vacuum induction furnace at a molar ratio of 1:2.4-2.8, and argon gas is introduced. After pre-reduction at 1350℃ for 30 min, the furnace is kept at 1550-1600℃ for 40-50 min to produce NiB through a carbothermic reduction reaction.

[0034] Slowly cool to 1200-1300℃ and keep warm to filter out impurities;

[0035] The mixture is poured into a water-cooled copper mold, and the cooling rate is controlled at 50-100℃ / s to obtain NiB master alloy. The mixture is then ground into NiB master alloy powder with a particle size ≤50μm.

[0036] In another preferred embodiment of the present invention, S3 specifically involves: controlling the particle size of nickel, chromium, cobalt, molybdenum, tungsten, titanium, and ruthenium powders to be 50-150 μm, pre-vacuum drying, and adding them to a vacuum induction furnace in the following order: bottom layer of high-melting-point metals W and Mo, middle layer of Ni, Co, and Cr, and top layer of low-melting-point metals Ti and Ru. The furnace is first evacuated using a mechanical pump, and then evacuated using a molecular pump to a depth of ≤5 × 10⁻⁶ μm. -3Pa, heat to 1950-2000℃ at a rate of 10-15℃ / min, hold for 30-40min to completely dissolve the refractory metal, cool to 1550-1600℃, and smelt at a constant temperature for 2-2.5h;

[0037] High-purity argon gas was introduced at a flow rate of 5-10 L / min, and degassing was performed at 50-80 Pa for 20-30 min.

[0038] After cooling to 1450-1500℃, passivated aluminum powder is added through a secondary feeding device in a vacuum chamber; Ni-B master alloy powder is added in 2-3 batches, with an interval of 3-5 minutes between each batch.

[0039] The temperature drops to 1400-1450℃, and the ingot is poured into a water-cooled copper mold at a pouring speed of 3-5 kg / min. The ingot is then removed from the furnace after cooling under argon protection.

[0040] In another preferred embodiment of the present invention, S4 specifically involves: using an electroslag remelting furnace to preheat and dehydrate the ternary slag system CaF2-Al2O3-CaO, so that the moisture content of the slag is ≤0.05%, and then loading it into the crystallizer; before smelting, the furnace body is evacuated to ≤10Pa and then high-purity argon gas is continuously introduced until the oxygen content in the furnace is ≤50ppm, and the crystallizer cooling water system is started simultaneously to maintain the temperature difference between the inlet and outlet of the cooling water ≤5℃ to prevent local overheating; the ingot is placed into the molten pool, and the voltage is controlled at 40-50V and the current at 2000-3000A, with intermittent pulses.

[0041] In another preferred embodiment of the present invention, S5 specifically involves: heating the ingot to 1150-1200°C using a high-speed forging machine and holding it at that temperature for 1.5-2 hours; employing a multi-directional forging process with alternating axial and radial deformation; achieving a final forging temperature of 900-950°C; and then air-cooling it to room temperature.

[0042] In another preferred embodiment of the present invention, S6 specifically involves: using a two-roll cold rolling mill and a chain cold drawing machine in tandem, cold rolling followed by cold drawing; immediately after cold rolling, the billet is transferred to an argon-protected annealing furnace, held at 750-800℃, slowly cooled at a rate of ≤30℃ / min, and then air-cooled; the surface of the billet is uniformly sprayed with a high-temperature resistant lubricant to a thickness of 5-10μm; after the lubricant layer has solidified, it is cold-drawn to obtain the finished product; and then polished in an electrolyte solution.

[0043] In another preferred embodiment of the present invention, S7 specifically involves: performing a solution treatment in a box-type vacuum furnace at 1080-1120°C under an argon atmosphere; after the solution treatment is completed, introducing 1.2MPa high-pressure nitrogen gas to force-cool to 300°C at a rate of 50-100°C / min; aging treatment at 750-800°C; followed by furnace cooling and air cooling to obtain a crack-resistant nickel-based high-temperature alloy.

[0044] The application of the aforementioned crack-resistant nickel-based superalloy in the preparation of hot-end components for aero-engines or gas turbines.

[0045] The method provided by this invention has the following technical effects:

[0046] 1. This invention uses rare earth oxides to passivate aluminum, forming a Y2O3 passivation layer, which effectively suppresses the precipitation of low-melting-point phases, significantly reduces the crack propagation rate under high-temperature cyclic loading, and optimizes the grain boundary bonding energy, thereby improving the long-term service stability of the alloy in oxidation-thermal corrosion coupled environments (such as hot-end components of aero-engines).

[0047] 2. This invention uses a Ni-B master alloy preparation process, employing carbothermic reduction and liquid filtration technology to avoid boron segregation and the formation of brittle borides, eliminate grain boundary stress concentration sources, and ensure that boron is uniformly distributed in the matrix. This suppresses intergranular fracture tendency and extends alloy life under high temperature and high stress conditions (such as 850℃ / 780MPa).

[0048] 3. This invention combines pulse electroslag remelting and multi-directional forging processes to refine grains and eliminate solidification defects, significantly reducing the risk of cracking during the cold rolling and cold drawing process of seamless pipes and improving the forming qualification rate of complex components (such as gas turbine ducts).

[0049] The following will further explain the concept, specific structure, and technical effects of the present invention in order to fully understand the purpose, features, and effects of the present invention. Detailed Implementation

[0050] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0051] Example 1: This example provides a crack-resistant nickel-based superalloy, which, by mass percentage, comprises the following components:

[0052] Cr: 18%;

[0053] Co: 15%;

[0054] Mo: 6%;

[0055] W:4%;

[0056] Al: 3%;

[0057] Ti:4%;

[0058] Ru:2%;

[0059] Y:1%;

[0060] B: 0.01%;

[0061] The balance is Ni and unavoidable impurities.

[0062] Al is passivated with Y2O3; B exists in the form of a Ni-B master alloy.

[0063] The specific preparation method includes the following steps:

[0064] S1. Pretreatment of aluminum – coating passivation + rare earth modification;

[0065] Aluminum powder (particle size ≤ 50 μm) and yttrium oxide powder (particle size ≤ 20 μm) were mixed and sintered at 400 °C for 2 h under argon protection, and then ground into passivated aluminum powder with a particle size ≤ 50 μm.

[0066] S2. Preparation of Ni-B master alloy;

[0067] Nickel oxide powder (NiO) was completely immersed in a boron-containing solution (0.5 mol / L NaBH4 + 0.2 mol / L citric acid), stirred at 60°C for 30 min, and oxidized in air at 250°C for 40 min to form a Ni-BO coating layer on the surface, thus obtaining pre-coated nickel oxide powder.

[0068] Boric anhydride powder (B2O3) and pre-coated nickel oxide powder were vacuum dried at 150℃ for 4 hours to remove adsorbed water and then sieved to a particle size ≤50μm to increase the reaction contact area.

[0069] B2O3 and NiO were mixed in a molar ratio of 1:1.2, and 0.5% of polyvinyl alcohol binder was added. The mixture was then cold isostatically pressed (300MPa) into a Φ50×50mm cylindrical block. The block was heated to 1000℃ under argon protection and held for 1.5h to produce liquid Ni(BO2)2.

[0070] Liquid Ni(BO2)2 and carbon powder were loaded into a vacuum induction furnace at a molar ratio of 1:2.8 (≤5×10). -3 Pa), purged with argon gas (5 L / min); held at 1350℃ for 30 min (pre-reduction); held at 1600℃ for 50 min to induce a carbothermic reduction reaction to produce NiB;

[0071] The temperature was slowly cooled to 1300℃ at 5℃ / min and held for 30min to promote uniform precipitation of the NiB phase. The mixture was then filtered using a zirconia porous ceramic filter (1.0mm pore size) to intercept inclusions.

[0072] The mixture is poured into a water-cooled copper mold and cooled at a rate of 100℃ / s to obtain NiB master alloy. The mixture is then ground into NiB master alloy powder with a particle size of ≤50μm.

[0073] S3. Vacuum induction melting and degassing treatment;

[0074] The particle size of nickel, chromium, cobalt, molybdenum, tungsten, titanium, and ruthenium powders was controlled to 150 μm. They were pre-dehydrated in a vacuum drying oven at 120℃ for 4 hours. Then, they were added to a 2000℃ vacuum induction furnace (vacuum degree ≤ 10⁻⁵) in the following order: bottom layer (high-melting-point metals W and Mo), middle layer (Ni, Co, and Cr), and top layer (low-melting-point metals Ti and Ru). -3 First, use a mechanical pump to pump to 10 Pa, then use a molecular pump to pump to ≤5 × 10 Pa. -3 Pa, heat to 2000℃ at a rate of 15℃ / min, hold for 40min to completely dissolve refractory metals (W, Mo), cool to 1600℃, and smelt at a constant temperature for 2.5h;

[0075] Argon gas with a purity of 99.9% was introduced at a flow rate of 10 L / min and degassed at 80 Pa for 30 min.

[0076] After cooling to 1500℃, passivated aluminum powder is added through a secondary feeding device in a vacuum chamber; Ni-B master alloy powder is added in three batches, with an interval of 5 minutes between each batch.

[0077] The temperature was lowered to 1450℃, and the ingot was poured into a water-cooled copper mold at a pouring speed of 5 kg / min to avoid oxidation caused by turbulence.

[0078] The ingot is cooled to 300°C under argon protection before being taken out of the furnace to reduce thermal stress cracking.

[0079] S4. Pulse electroslag remelting;

[0080] An electroslag remelting furnace was used to preheat and dehydrate the ternary slag system CaF2-Al2O3-CaO (mass ratio 55:30:15) at 800℃ for more than 4 hours, so that the slag moisture content was ≤0.05%, and then it was loaded into the crystallizer. Before melting, the furnace body was evacuated to ≤10Pa and high-purity argon gas was continuously introduced until the oxygen content in the furnace was ≤50ppm. At the same time, the cooling water system of the crystallizer was started, the flow rate was controlled at 12m³ / h and the temperature difference between the inlet and outlet of the cooling water was maintained at ≤5℃ to prevent local overheating. During the arc initiation stage, a molten pool was established with a voltage of 45V and a current of 2500A. The ingot was put in and after entering a steady state, the voltage was controlled at 50V and the current at 3000A. A pulse was activated for 30s every 5 minutes of melting. The pulse power supply parameters were frequency 120Hz, pulse width 400ms and peak current 450A.

[0081] S5. Forging of blanks;

[0082] Using a 1000-ton high-speed forging mill, the ingot is heated to 1200℃ and held for 2 hours. A multi-directional forging process with alternating axial and radial deformation is adopted (axial upsetting → radial elongation → secondary axial upsetting → radial shaping) to ensure that the total forging ratio is ≥8 and the final forging temperature is 950℃. Then, it is air-cooled to room temperature.

[0083] S6. Cold rolled and cold drawn;

[0084] The process employs a two-roll cold rolling mill (diameter reduction rate ≤18%) and a chain cold drawing machine (elongation coefficient ≤2.0) in tandem, with cold rolling followed by cold drawing: After cold rolling, the billet is immediately transferred to an argon-protected annealing furnace, held at 800℃ for 2 hours, and slowly cooled to 600℃ at a rate of ≤30℃ / min, followed by air cooling. The surface of the billet is uniformly sprayed with a high-temperature resistant lubricant (WS2 powder, the lubrication characteristics of WS2 are basically unaffected at temperatures below 400℃) to a thickness of 10μm. After the lubricant layer has solidified, it is cold-drawn to obtain a finished product (seamless steel pipe) with an outer diameter of φ50mm and a wall thickness of 5mm. After confirming that there are no defects through eddy current testing, it is placed in a perchloric acid-ethanol electrolyte (volume ratio 1:9) at -10±2℃ and electropolished at 18V voltage for 8 minutes with a lead plate as the cathode.

[0085] S7. Heat treatment annealing;

[0086] In a box-type vacuum furnace (vacuum degree ≤10) -2 The solution was prepared at 1120℃ under an argon atmosphere for 2 hours. After solution treatment, 1.2MPa high-pressure nitrogen gas was immediately introduced and the temperature was rapidly cooled to 300℃ at a rate of 100℃ / min. Then, the temperature was raised to 800℃ for aging treatment for 8 hours. After furnace cooling to 500℃, the temperature was air-cooled to obtain a crack-resistant nickel-based superalloy.

[0087] Example 2: This example provides a crack-resistant nickel-based superalloy, which, by mass percentage, comprises the following components:

[0088] Cr: 12%;

[0089] Co: 8%;

[0090] Mo: 3%;

[0091] W:2%;

[0092] Al: 1%;

[0093] Ti:2%;

[0094] Ru: 0.5%;

[0095] Y: 0.3%;

[0096] B: 0.002%;

[0097] The balance is Ni and unavoidable impurities.

[0098] Al is passivated with Y2O3; B exists in the form of a Ni-B master alloy.

[0099] The specific preparation method includes the following steps:

[0100] S1. Pretreatment of aluminum – coating passivation + rare earth modification;

[0101] Aluminum powder (particle size ≤ 50 μm) and yttrium oxide powder (particle size ≤ 20 μm) were mixed and sintered at 380 °C for 1 h under argon protection, and then ground into passivated aluminum powder with a particle size ≤ 50 μm.

[0102] S2. Preparation of Ni-B master alloy;

[0103] Nickel oxide powder (NiO) was completely immersed in a boron-containing solution (0.5 mol / L NaBH4 + 0.2 mol / L citric acid), stirred at 60°C for 30 min, and oxidized in air at 250°C for 40 min to form a Ni-BO coating layer on the surface, thus obtaining pre-coated nickel oxide powder.

[0104] Boric anhydride powder (B2O3) and pre-coated nickel oxide powder were vacuum dried at 150℃ for 4 hours to remove adsorbed water and then sieved to a particle size ≤50μm to increase the reaction contact area.

[0105] B2O3 and NiO were mixed in a 1:1 molar ratio, and 0.5% of polyvinyl alcohol binder was added. The mixture was then cold isostatically pressed (300MPa) into a Φ50×50mm cylindrical block. The block was heated to 950℃ under argon protection and held for 1 hour to produce liquid Ni(BO2)2.

[0106] Liquid Ni(BO2)2 and carbon powder were loaded into a vacuum induction furnace at a molar ratio of 1:2.4 (≤5×10). -3 Pa), purged with argon gas (5L / min); held at 1350℃ for 30min (pre-reduction); held at 1550℃ for 40min to induce carbothermic reduction reaction to produce NiB;

[0107] The temperature was slowly cooled to 1200℃ at 5℃ / min and held for 30min to promote uniform precipitation of the NiB phase. The mixture was then filtered using a zirconia porous ceramic filter (0.5mm pore size) to intercept inclusions.

[0108] The mixture is poured into a water-cooled copper mold, and the cooling rate is controlled at 50℃ / s to obtain NiB master alloy. The mixture is then ground into NiB master alloy powder with a particle size ≤50μm.

[0109] S3. Vacuum induction melting and degassing treatment;

[0110] The particle size of nickel, chromium, cobalt, molybdenum, tungsten, titanium, and ruthenium powders was controlled to 50 μm. They were pre-dehydrated in a vacuum drying oven at 120℃ for 4 hours. Then, they were added to a 2000℃ vacuum induction furnace (vacuum degree ≤10) in the following order: bottom layer (high melting point metals W and Mo), middle layer (Ni, Co, and Cr), and top layer (low melting point metals Ti and Ru). -3 First, use a mechanical pump to pump to 10 Pa, then use a molecular pump to pump to ≤5 × 10 Pa. -3 Pa, heat to 1950℃ at a rate of 10℃ / min, hold for 30min to completely dissolve the refractory metals (W, Mo), cool to 1550℃, and smelt at a constant temperature for 2h;

[0111] Argon gas with a purity of 99.9% was introduced at a flow rate of 5 L / min and degassed at 50 Pa for 20 min.

[0112] After cooling to 1450℃, passivated aluminum powder is added through a secondary feeding device in a vacuum chamber; Ni-B master alloy powder is added in two batches, with a 3-minute interval between each batch.

[0113] The temperature was lowered to 1400℃, and the ingot was poured into a water-cooled copper mold at a pouring speed of 3 kg / min to avoid oxidation caused by turbulence.

[0114] The ingot is cooled to 300°C under argon protection before being taken out of the furnace to reduce thermal stress cracking.

[0115] S4. Pulse electroslag remelting;

[0116] An electroslag remelting furnace was used to preheat and dehydrate the ternary slag system CaF2-Al2O3-CaO (mass ratio 55:30:15) at 800℃ for more than 4 hours, so that the slag moisture content was ≤0.05%, and then it was loaded into the crystallizer. Before melting, the furnace body was evacuated to ≤10Pa and high-purity argon gas was continuously introduced until the oxygen content in the furnace was ≤50ppm. At the same time, the cooling water system of the crystallizer was started, the flow rate was controlled at 12m³ / h and the temperature difference between the inlet and outlet of the cooling water was maintained at ≤5℃ to prevent local overheating. During the arc initiation stage, a molten pool was established using a voltage of 45V and a current of 2500A. The ingot was then put in and after entering a steady state, the voltage was controlled at 40V and the current at 2000A. A pulse was activated for 30s every 5 minutes of melting. The pulse power supply parameters were frequency 120Hz, pulse width 400ms and peak current 450A.

[0117] S5. Forging of blanks;

[0118] Using a 1000-ton high-speed forging mill, the ingot is heated to 1150℃ and held for 1.5 hours. A multi-directional forging process with alternating axial and radial deformation is adopted (axial upsetting → radial elongation → secondary axial upsetting → radial shaping) to ensure that the total forging ratio is ≥8 and the final forging temperature is 900℃. Then, it is air-cooled to room temperature.

[0119] S6. Cold rolled and cold drawn;

[0120] The process employs a two-roll cold rolling mill (diameter reduction rate ≤18%) and a chain cold drawing machine (elongation coefficient ≤2.0) in tandem, with cold rolling followed by cold drawing: After cold rolling, the billet is immediately transferred to an argon-protected annealing furnace, held at 750℃ for 2 hours, and slowly cooled to 600℃ at a rate of ≤30℃ / min, followed by air cooling. The surface of the billet is uniformly sprayed with a high-temperature resistant lubricant (WS2 powder) to a thickness of 5μm. After the lubricant layer has solidified, it is cold-drawn to obtain a finished product (seamless steel pipe) with an outer diameter of φ40mm and a wall thickness of 3mm. After confirming that there are no defects through eddy current testing, the surface is treated by electropolishing in a perchloric acid-ethanol electrolyte (volume ratio 1:9) at -10±2℃ with a lead plate as the cathode and a voltage of 18V for 8 minutes.

[0121] S7. Heat treatment annealing;

[0122] In a box-type vacuum furnace (vacuum degree ≤10) -2 The solution was prepared at 1090℃ under an argon atmosphere for 2 hours. After solution treatment, 1.2MPa high-pressure nitrogen gas was immediately introduced and the temperature was rapidly cooled to 300℃ at a rate of 50℃ / min. Then, the temperature was raised to 780℃ for aging treatment for 8 hours. After furnace cooling to 500℃, the temperature was air-cooled to obtain a crack-resistant nickel-based superalloy.

[0123] Example 3: This example provides a crack-resistant nickel-based superalloy, which, by mass percentage, comprises the following components:

[0124] Cr: 15%;

[0125] Co: 12%;

[0126] Mo: 5%;

[0127] W:3%;

[0128] Al:2%;

[0129] Ti:3%;

[0130] Ru: 0.9%;

[0131] Y: 0.6%;

[0132] B: 0.008%;

[0133] The balance is Ni and unavoidable impurities.

[0134] Al is passivated with Y2O3; B exists in the form of a Ni-B master alloy.

[0135] The specific preparation method includes the following steps:

[0136] S1. Pretreatment of aluminum – coating passivation + rare earth modification;

[0137] Aluminum powder (particle size ≤ 50 μm) and yttrium oxide powder (particle size ≤ 20 μm) were mixed and sintered at 385 °C for 1.5 h under argon protection, and then ground into passivated aluminum powder with a particle size ≤ 50 μm.

[0138] S2. Preparation of Ni-B master alloy;

[0139] Nickel oxide powder (NiO) was completely immersed in a boron-containing solution (0.5 mol / L NaBH4 + 0.2 mol / L citric acid), stirred at 60°C for 30 min, and oxidized in air at 250°C for 40 min to form a Ni-BO coating layer on the surface, thus obtaining pre-coated nickel oxide powder.

[0140] Boric anhydride powder (B2O3) and pre-coated nickel oxide powder were vacuum dried at 150℃ for 4 hours to remove adsorbed water and then sieved to a particle size ≤50μm to increase the reaction contact area.

[0141] B2O3 and NiO were mixed in a molar ratio of 1:1.1, and 0.5% of polyvinyl alcohol binder was added. The mixture was then cold isostatically pressed (300MPa) into a Φ50×50mm cylindrical block. The block was heated to 980℃ under argon protection and held for 1.5h to produce liquid Ni(BO2)2.

[0142] Liquid Ni(BO2)2 and carbon powder were loaded into a vacuum induction furnace at a molar ratio of 1:2.5 (≤5×10). -3 Pa), purged with argon gas (5 L / min); held at 1350℃ for 30 min (pre-reduction); held at 1580℃ for 48 min to undergo carbothermic reduction reaction to generate NiB;

[0143] The temperature was slowly cooled to 1280℃ at 5℃ / min and held for 30min to promote uniform precipitation of the NiB phase. The mixture was then filtered using a zirconia porous ceramic filter (0.8mm pore size) to intercept inclusions.

[0144] The mixture is poured into a water-cooled copper mold and cooled at a rate of 80°C / s to obtain a NiB master alloy. The mixture is then ground into NiB master alloy powder with a particle size of ≤50μm.

[0145] S3. Vacuum induction melting and degassing treatment;

[0146] The particle size of nickel, chromium, cobalt, molybdenum, tungsten, titanium, and ruthenium powders was controlled to 100 μm. They were pre-dehydrated in a vacuum drying oven at 120℃ for 4 hours. The powders were then added to a 2000℃ vacuum induction furnace (vacuum degree ≤10) in the following order: bottom layer (high-melting-point metals W and Mo), middle layer (Ni, Co, and Cr), and top layer (low-melting-point metals Ti and Ru). -3 First, use a mechanical pump to pump to 10 Pa, then use a molecular pump to pump to ≤5 × 10 Pa. -3Pa, heat to 1970℃ at a rate of 12℃ / min, hold for 34min to completely dissolve the refractory metals (W, Mo), cool to 1590℃, and smelt at a constant temperature for 2h;

[0147] Argon gas with a purity of 99.9% was introduced at a flow rate of 8 L / min and degassed at 70 Pa for 28 min.

[0148] After cooling to 1480℃, passivated aluminum powder is added through a secondary feeding device in a vacuum chamber; Ni-B master alloy powder is added in three batches, with an interval of 4 minutes between each batch.

[0149] The temperature was lowered to 1420℃, and the ingot was poured into a water-cooled copper mold at a pouring speed of 4 kg / min to avoid oxidation caused by turbulence.

[0150] The ingot is cooled to 300°C under argon protection before being taken out of the furnace to reduce thermal stress cracking.

[0151] S4. Pulse electroslag remelting;

[0152] An electroslag remelting furnace was used to preheat and dehydrate the ternary slag system CaF2-Al2O3-CaO (mass ratio 55:30:15) at 800℃ for more than 4 hours, so that the slag moisture content was ≤0.05%, and then it was loaded into the crystallizer. Before melting, the furnace body was evacuated to ≤10Pa and high-purity argon gas was continuously introduced until the oxygen content in the furnace was ≤50ppm. At the same time, the cooling water system of the crystallizer was started, the flow rate was controlled at 12m³ / h and the temperature difference between the inlet and outlet of the cooling water was maintained at ≤5℃ to prevent local overheating. During the arc initiation stage, a molten pool was established with a voltage of 45V and a current of 2500A. The ingot was put in and after entering a steady state, the voltage was controlled at 47V and the current at 2200A. A pulse was activated for 30s every 5 minutes of melting. The pulse power supply parameters were frequency 120Hz, pulse width 400ms and peak current 450A.

[0153] S5. Forging of blanks;

[0154] Using a 1000-ton high-speed forging mill, the ingot is heated to 1180℃ and held for 1.5 hours. A multi-directional forging process with alternating axial and radial deformation is adopted (axial upsetting → radial elongation → secondary axial upsetting → radial shaping) to ensure that the total forging ratio is ≥8 and the final forging temperature is 920℃. Then, it is air-cooled to room temperature.

[0155] S6. Cold rolled and cold drawn;

[0156] The process employs a two-roll cold rolling mill (diameter reduction rate ≤18%) and a chain cold drawing machine (elongation coefficient ≤2.0) in tandem, with cold rolling followed by cold drawing: After cold rolling, the billet is immediately transferred to an argon-protected annealing furnace, held at 770℃ for 2 hours, and slowly cooled to 600℃ at a rate of ≤30℃ / min, followed by air cooling. The surface of the billet is uniformly sprayed with a high-temperature resistant lubricant (WS2 powder) to a thickness of 8μm. After the lubricant layer has solidified, it is cold-drawn to obtain a finished product (seamless steel pipe) with an outer diameter of φ30mm and a wall thickness of 3mm. After confirming that there are no defects through eddy current testing, the surface is placed in a perchloric acid-ethanol electrolyte (volume ratio 1:9) at -10±2℃ and electropolished at 18V voltage for 8 minutes with a lead plate as the cathode.

[0157] S7. Heat treatment annealing;

[0158] In a box-type vacuum furnace (vacuum degree ≤10) -2 The solution was prepared at 1110℃ under an argon atmosphere for 2 hours. After solution treatment, 1.2MPa high-pressure nitrogen was immediately introduced and the temperature was rapidly cooled to 300℃ at a rate of 80℃ / min. Then, the temperature was raised to 770℃ for aging treatment for 8 hours. After furnace cooling to 500℃, the temperature was air-cooled to obtain a crack-resistant nickel-based superalloy.

[0159] Comparative Example 1: The difference from Example 3 is that Al was not passivated by Y2O3, but was directly added to the vacuum induction furnace in the form of aluminum powder and yttrium oxide powder.

[0160] Comparative Example 2: The difference from Example 3 is that B is not added in the form of NiB, but directly added to the vacuum induction furnace in the form of boron powder.

[0161] Comparative Example 3: The difference from Example 3 is that Al, Y2O3 and B are added directly to the vacuum induction furnace in powder form.

[0162] Experimental Example: 1. Long-term high-temperature and high-stress fatigue crack propagation rate tests were conducted on the products prepared in Examples 1-3 and Comparative Examples 1-3. The steps are as follows:

[0163] A φ20mm×20mm sample was prepared with a pre-made mechanical notch (depth 2.5mm, included angle 30°) and the surface was polished to Ra≤0.2μm. After the sample was clamped and fixed, it was heated to the target temperature (850℃) at a rate of ≤5℃ / min and held for 1000h, while a constant extrusion pressure of 780MPa was applied to the sample. Finally, the sample was taken out, ground and polished, and the length L1 (μm) and width W1 (μm) of the main crack were measured under a metallographic microscope.

[0164] 2. The fatigue crack propagation rate resistance tests under cyclic loading were conducted on the products prepared in Examples 1-3 and Comparative Examples 1-3, as follows:

[0165] A φ20mm×20mm sample was prepared with a pre-formed mechanical notch (depth 2.5mm, included angle 30°) and the surface was polished to Ra≤0.2μm. After the sample was clamped and fixed, it was placed in a supercritical water vapor atmosphere at 650℃ (simulating service in a combustion gas environment), and a compressive force of 850MPa was applied to the sample for 5s every 30s. After 1000h of cycling, the sample was taken out, ground and polished, and the length L2 (μm) and width W2 (μm) of the main crack were measured under a metallographic microscope.

[0166] The results are shown in the table below:

[0167]

[0168] As shown in the table above, the passivation treatment of aluminum with yttrium oxide significantly reduces the crack propagation rate of the crack-resistant nickel-based superalloy under 650℃ cyclic loading.

[0169] The Ni-B master alloy has a density that matches the nickel matrix, enabling uniform dissolution through liquid-phase diffusion and suppressing the oxidation and volatilization of boron; while boron powder (melting point 2300℃, density approximately 2.3 g / cm³) 3 When added directly, B2O3 impurities tend to float and agglomerate. During smelting, these surface B2O3 impurities form low-melting-point eutectics (such as Cr-BO systems, melting point <900℃), promoting grain boundary segregation and forming coarse, brittle borides, which become stress concentration sources. Under load, cracks preferentially initiate and propagate along the brittle borides, leading to intergranular fracture. As shown in the table above, the crack propagation rate under 850℃ / 780MPa stress in Comparative Example 2 is significantly higher than that in the Example.

[0170] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A crack-resistant nickel-based superalloy, characterized in that, By mass percentage, it includes the following components: Cr: 12-18%; Co: 8-15%; Mo: 3-6%; W: 2-4%; Al: 1-3%; Ti: 2-4%; Ru: 0.5-2%; Y: 0.3-1%; B: 0.002-0.01%; the balance being Ni and unavoidable impurities. Al is passivated with Y2O3; B exists in the form of a Ni-B master alloy.

2. A method for preparing the crack-resistant nickel-based superalloy as described in claim 1, characterized in that, Includes the following steps: S1. Pretreatment of aluminum; Aluminum powder and yttrium oxide powder are mixed, sintered under argon protection, and then ground to obtain passivated aluminum powder; S2. Preparation of Ni-B master alloy; Nickel oxide powder was immersed in a boron-containing solution and stirred, then oxidized and dried in air at 250°C to obtain pre-coated nickel oxide powder. Boric anhydride powder and pre-coated nickel oxide powder were vacuum dried, sieved and mixed, polyvinyl alcohol binder was added, cold isostatic pressing was performed, and then heated under argon protection to generate liquid Ni(BO2)2. Liquid Ni(BO2)2 and carbon powder were pre-reduced at 1350℃ for 30 min, and then reacted at a constant temperature of 1550-1600℃ to generate NiB; the mixture was then slowly cooled to 1200-1300℃ and kept at that temperature, and impurities were filtered out. NiB master alloy was obtained by casting and NiB master alloy powder was obtained by grinding. S3. Vacuum induction melting and degassing treatment; The dried nickel, chromium, cobalt, molybdenum, tungsten, titanium, and ruthenium powders are added to a vacuum induction furnace, evacuated to a vacuum, heated to 1950-2000℃, and then cooled to 1550-1600℃ for constant-temperature melting; high-purity argon is then introduced for degassing. After cooling to 1450-1500℃, add passivated aluminum powder; add Ni-B master alloy powder in batches. The temperature is reduced to 1400-1450℃, and the furnace is tilted to pour the ingot into a water-cooled copper mold to obtain an ingot; the ingot is cooled under argon protection and then removed from the furnace. S4. Pulse electroslag remelting; An electroslag remelting furnace is used to load preheated and dehydrated ternary slag system CaF2-Al2O3-CaO into the crystallizer; before melting, the furnace body is evacuated and high-purity argon gas is introduced, and the crystallizer cooling water system is started simultaneously; the ingot is put into the molten pool and intermittently pulsed. S5. Forging of blanks; The ingot is heated to 1150-1200℃ using a high-speed forging mill and held at that temperature. A multi-directional forging process with alternating axial and radial deformation is then employed, followed by air cooling to room temperature. S6. Cold rolled and cold drawn; The billet is annealed immediately after cold rolling, and a high-temperature resistant lubricant is evenly sprayed onto the surface of the billet. After the lubricant layer has solidified, it is cold-drawn to obtain the finished product; it is then polished in an electrolyte solution. S7. Heat treatment annealing; After solution treatment, high-pressure nitrogen gas at 1.2 MPa is introduced and the temperature is rapidly cooled to 300°C at a rate of 50-100°C / min; aging treatment is then performed, followed by furnace cooling and air cooling to obtain a crack-resistant nickel-based superalloy.

3. The method for preparing the crack-resistant nickel-based superalloy as described in claim 2, characterized in that, S1 specifically involves mixing aluminum powder and yttrium oxide powder, sintering at 380-400℃ for 1-2 hours under argon protection, and grinding the mixture into passivated aluminum powder with a particle size ≤50μm.

4. The method for preparing the crack-resistant nickel-based superalloy as described in claim 2, characterized in that, S2 specifically involves: completely immersing nickel oxide powder in a boron-containing solution and stirring, then oxidizing and drying it in air at 250°C to generate a Ni-BO coating layer on the surface, thus obtaining pre-coated nickel oxide powder; Boric anhydride powder and pre-coated nickel oxide powder were vacuum dried to remove adsorbed water and sieved to a particle size ≤50μm. B2O3 and NiO are mixed in a molar ratio of 1:1-1.2, polyvinyl alcohol binder is added, and the mixture is cold isostatically pressed into cylindrical blocks. The blocks are then heated to 950-1000℃ under argon protection and held for 1-1.5 hours to produce liquid Ni(BO2)2. Liquid Ni(BO2)2 and carbon powder are loaded into a vacuum induction furnace at a molar ratio of 1:2.4-2.8, and argon gas is introduced. After pre-reduction at 1350℃ for 30 min, the furnace is kept at 1550-1600℃ for 40-50 min to produce NiB through a carbothermic reduction reaction. Slowly cool to 1200-1300℃ and keep warm to filter out impurities; The mixture is poured into a water-cooled copper mold, and the cooling rate is controlled at 50-100℃ / s to obtain NiB master alloy. The mixture is then ground into NiB master alloy powder with a particle size ≤50μm.

5. The method for preparing the crack-resistant nickel-based superalloy as described in claim 2, characterized in that, S3 specifically involves controlling the particle size of nickel, chromium, cobalt, molybdenum, tungsten, titanium, and ruthenium powders to 50-150 μm, pre-drying them under vacuum, and adding them to a vacuum induction furnace in the following order: bottom layer of high-melting-point metals W and Mo, middle layer of Ni, Co, and Cr, and top layer of low-melting-point metals Ti and Ru. The furnace is first evacuated using a mechanical pump, then evacuated using a molecular pump until the powder reaches ≤5 × 10⁻⁶ μm. -3 Pa, heat to 1950-2000℃ at a rate of 10-15℃ / min, hold for 30-40min to completely dissolve the refractory metal, cool to 1550-1600℃, and smelt at a constant temperature for 2-2.5h; High-purity argon gas was introduced at a flow rate of 5-10 L / min, and degassing was performed at 50-80 Pa for 20-30 min. After cooling to 1450-1500℃, passivated aluminum powder is added through a secondary feeding device in a vacuum chamber; Ni-B master alloy powder is added in 2-3 batches, with an interval of 3-5 minutes between each batch. The temperature drops to 1400-1450℃, and the ingot is poured into a water-cooled copper mold at a pouring speed of 3-5 kg / min. The ingot is then removed from the furnace after cooling under argon protection.

6. The method for preparing the crack-resistant nickel-based superalloy as described in claim 2, characterized in that, S4 specifically involves: using an electroslag remelting furnace to preheat and dehydrate the ternary slag system CaF2-Al2O3-CaO, ensuring the slag material has a moisture content of ≤0.05%, and then loading it into the crystallizer; before smelting, the furnace body is evacuated to ≤10Pa and then high-purity argon gas is continuously introduced until the oxygen content in the furnace is ≤50ppm, and the crystallizer cooling water system is started simultaneously to maintain a temperature difference of ≤5℃ between the inlet and outlet of the cooling water to prevent local overheating; the ingot is then placed into the molten pool, with the voltage controlled at 40-50V and the current at 2000-3000A, using intermittent pulses.

7. The method for preparing the crack-resistant nickel-based superalloy as described in claim 2, characterized in that, S5 specifically involves heating the ingot to 1150-1200℃ using a high-speed forging machine and holding it at that temperature for 1.5-2 hours. A multi-directional forging process with alternating axial and radial deformation is then employed, with a final forging temperature of 900-950℃, followed by air cooling to room temperature.

8. The method for preparing the crack-resistant nickel-based superalloy as described in claim 2, characterized in that, S6 specifically involves the coordinated operation of a two-roll cold rolling mill and a chain cold drawing machine, with cold rolling followed by cold drawing: after cold rolling, the billet is immediately transferred to an argon-protected annealing furnace, held at 750-800℃, and then slowly cooled at a rate of ≤30℃ / min before air cooling. The surface of the billet is uniformly sprayed with a high-temperature resistant lubricant to a thickness of 5-10μm. After the lubricant layer has solidified, it is cold-drawn to obtain the finished product. Polishing is performed by placing the sample in an electrolyte solution.

9. The method for preparing the crack-resistant nickel-based superalloy as described in claim 2, characterized in that, S7 is specifically carried out in a box-type vacuum furnace, with solution treatment at 1080-1120℃ in an argon atmosphere; after solution treatment, high-pressure nitrogen gas of 1.2MPa is introduced and the temperature is strongly cooled to 300℃ at a rate of 50-100℃ / min; the temperature is then raised to 750-800℃ for aging treatment, followed by furnace cooling and air cooling to obtain a crack-resistant nickel-based high-temperature alloy.

10. The application of the crack-resistant nickel-based superalloy as described in claim 1 in the preparation of hot-end components for aero-engines or gas turbines.

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