A high-temperature fatigue-resistant material of 901 high-temperature alloy and its preparation method

Abstract

The present invention relates to the field of high-temperature alloys and provides a high-temperature fatigue-resistant material of a 901 high-temperature alloy and a preparation method thereof. The method includes raw material proportioning and smelting, electroslag remelting, homogenization treatment, hot rolling, solution treatment, aging treatment, stabilization treatment, machining and plasma nitriding treatment. By optimizing the alloy composition and process parameters, the γ phase grain refinement, the uniform dispersion distribution of the Ni3(Ti,Al) precipitation phase, and the reasonable control of the morphology and volume fraction of the MC type carbide are ensured to improve the precipitation strengthening and creep resistance of the material. Plasma nitriding forms a nitriding layer containing CrN, γ-FeNi and Ni4N, which improves the surface hardness and crack propagation resistance while maintaining good toughness. Compared with the existing technology, the present invention significantly improves the fatigue life and high-temperature stability of the alloy, is suitable for high-temperature service environments such as aircraft engines and gas turbines, and has a wide range of application value.

Description

Technical Field

[0001] The present invention relates to the field of high-temperature alloys, and in particular to a high-temperature fatigue-resistant material of a 901 high-temperature alloy and a preparation method thereof. Background Art

[0002] In the aerospace, energy, and high-end manufacturing sectors, 901 superalloy is widely used in critical load-bearing structures such as aeroengine blades, turbine disks, and gas turbine hot-end components due to its excellent high-temperature strength, creep resistance, and corrosion resistance. These components are subjected to long-term high temperatures, high stresses, and complex environmental loads, requiring excellent fatigue resistance to ensure structural safety and service life. Under high-temperature alternating loads, fatigue crack initiation and propagation are key factors affecting service life. Therefore, high-temperature fatigue resistance is a core requirement in the design and optimization of superalloy materials. First, the alloy must possess a stable microstructure to resist microstructural evolution at high temperatures and prevent performance degradation caused by coarsening of precipitation phases or instability of phase interfaces. Second, a uniform dispersion of precipitation-strengthening phases is crucial for enhancing the alloy's fatigue crack initiation resistance. Appropriately controlling the size, volume fraction, and distribution of the γ' phase effectively enhances matrix strengthening. Furthermore, the precipitation of carbides and other secondary phases along grain boundaries should ensure strengthening while preventing excessive growth that could lead to increased brittleness, thereby improving the material's overall mechanical properties. Surface strengthening technology is also important. Surface modification methods such as nitriding can improve surface hardness and crack propagation resistance, further delaying fatigue failure. In summary, developing 901 superalloys with high-temperature stability, excellent precipitation strengthening, and optimized grain boundary structure, supplemented by surface strengthening technology, for high-temperature service conditions, is key to improving high-temperature fatigue resistance, extending service life, and enhancing safety.

[0003] While existing technologies have made some progress in optimizing the fatigue resistance of high-temperature alloys, numerous deficiencies remain. For example, Chinese Patent Publication No. CN102719682B discloses a method for preparing a 901 high-temperature alloy. While this method improves the alloy's high-temperature strength through optimized composition and heat treatment, its fatigue performance remains limited. A key issue is that the alloy's microstructure readily evolves during long-term service, leading to the aggregation and coarsening of precipitates, which in turn reduces the precipitation strengthening effect and degrades the material's durability under high-temperature fatigue loading. Furthermore, while MC carbides distributed along grain boundaries provide some strengthening, their large size makes them susceptible to crack initiation under fatigue loading, accelerating the fatigue failure process. Existing surface modification techniques, such as conventional gas nitriding or laser surface treatment, can improve surface hardness to a certain extent, but struggle to achieve a uniform and stable nitrided layer. This results in fatigue cracks easily propagating at interfaces, reducing overall fatigue life. Furthermore, optimization of the heat treatment process requires further refined control to ensure the stability and uniformity of the precipitates and avoid localized stress concentrations caused by structural inhomogeneities. Therefore, the existing 901 high-temperature alloy still needs to be further optimized in terms of microstructure stability, precipitation phase uniformity, grain boundary strengthening strategy and surface modification technology to achieve better high-temperature fatigue resistance and meet more stringent service requirements in the future. Summary of the Invention

[0004] (1) Technical problems solved

[0005] The purpose of the present invention is to provide a high-temperature fatigue-resistant material of a 901 high-temperature alloy and a preparation method thereof, so as to solve the problem that the current 901 high-temperature alloy has insufficient fatigue life and high-temperature stability.

[0006] (2) Technical solution

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A method for preparing a high-temperature fatigue-resistant material of a 901 high-temperature alloy comprises the following steps:

[0009] S1. Raw Material Proportioning and Melting: The high-temperature alloy raw materials are placed in a vacuum induction melting furnace for melting. After melting, they are rapidly cast to obtain a cast ingot. The cast ingot is then placed in an electroslag remelting furnace for electroslag remelting, using the cast ingot as an electrode.

[0010] S2 homogenization and hot rolling: The electroslag remelting ingot of step S1 is placed in a muffle furnace, followed by homogenization and hot rolling to obtain a rolled plate;

[0011] S3 three-step heat treatment: the plate after step S2 rolling is sequentially subjected to solution treatment, aging treatment and stabilization treatment to obtain a heat-treated plate;

[0012] S4. Machining and surface treatment: The plate after the heat treatment in step S3 is first machined and then subjected to plasma nitriding treatment to obtain a high-temperature fatigue-resistant material of 901 high-temperature alloy.

[0013] Furthermore, the raw materials of the high-temperature alloy in step S1 include, by weight percentage, 41.0-42.5% Ni, 11.0-13.0% Cr, 5.0-5.8% Mo, 2.2-2.5% Ti, 0.30-0.40% Al, 0.20-0.35% Si, 0.50-0.65% Mn, 0.40-0.50% Co, 0.02-0.09% C, 0.015-0.025% B, ≤0.001% S, ≤0.001% P, and the balance is Fe and unavoidable impurities.

[0014] Furthermore, the smelting process in step S1 is as follows: -3 Pa vacuum environment, heating to 1500-1550° C. at a heating rate of 5-10° C. / min, and keeping warm for 30-60 minutes, during which the stirring rate is controlled at 10-20 rpm.

[0015] Furthermore, the electroslag remelting process in step S1 is as follows: using CaO-Al2O3-MgO slag system as a refining agent, remelting is performed under the conditions of 30-35V, 500-800A, and the cooling water temperature is maintained at 20-30°C during the smelting process to ensure uniform cooling of the ingot.

[0016] The present invention adopts the design of optimized raw material ratio, smelting and remelting process mainly to enhance the high temperature fatigue resistance of 901 high temperature alloy. By rationally selecting the content of elements such as Ni, Cr, Mo, Ti, Al, etc., it is ensured that the alloy has excellent creep resistance and structural stability in high temperature environment. Among them, Ni as a matrix element provides high temperature strength, Cr gives the alloy antioxidant and corrosion resistance, Mo improves the thermal stability of the alloy through solid solution strengthening, and Ti and Al jointly promote the formation of Ni3 (Ti, Al) precipitation phase, thereby enhancing the precipitation strengthening effect of the material. Using vacuum induction melting process, in 10 -3Under a vacuum environment of 1000 Pa, the temperature is heated to 1500-1550°C at an appropriate heating rate and maintained for a certain period of time to uniformly melt the alloy components. At the same time, the uniformity of the alloy components is controlled by stirring to reduce segregation. Subsequently, the ingot is quickly cast to reduce the risk of structural coarsening and provide a good initial structure for subsequent remelting and refining. During the electroslag remelting stage, the CaO-Al2O3-MgO slag system is used as a refining agent and remelting is carried out under specific voltage and current conditions. This not only further removes inclusions and harmful elements, improves the purity of the alloy, but also improves the density and uniformity of the ingot. This process maintains uniform cooling of the ingot by controlling the cooling water temperature, thereby optimizing the microstructure, reducing segregation and casting defects, and providing an excellent structural foundation for subsequent hot processing. Through the above design, the present invention achieves a synergistic effect between the various components, ensuring the high-temperature strength of the alloy and optimizing the uniformity of the microstructure, providing a guarantee for improving the fatigue resistance of the alloy.

[0017] Furthermore, the homogenization and hot rolling process of step S2 is as follows: heating to 1160-1180°C at a heating rate of 5-10°C / min and keeping warm for 120-180min, then cooling to 1100-1150°C at a cooling rate of 10-15°C / min, and hot rolling, the deformation of a single rolling pass is controlled at 10-20%, the total deformation is 50-70%, and slowly cooling to room temperature after rolling is completed.

[0018] The present invention adopts the design of homogenization treatment and hot rolling process mainly to enhance the high-temperature fatigue resistance of 901 high-temperature alloy. Through homogenization treatment, the component segregation in the cast structure is fully diffused, the unevenness of element distribution is reduced, and the morphology and distribution of the γ phase and Ni3 (Ti, Al) precipitation phase are optimized, providing a stable organizational basis for subsequent hot processing. The control of the cooling rate after homogenization ensures the stable evolution of the organization, so that the material has good plasticity and uniformity when entering the hot rolling stage. During the hot rolling process, the occurrence of dynamic recrystallization is regulated by a reasonable single-pass deformation amount, the grains are refined and the grain boundary structure is improved, thereby improving the material's resistance to fatigue crack initiation. The appropriate total deformation amount ensures that the alloy forms a stable dislocation structure during the deformation process, enhances the interaction of dislocations, and thus improves fatigue resistance. In addition, after rolling is completed, a slow cooling method is adopted to fully release the residual stress generated during the processing and reduce the adverse effects of stress concentration on fatigue crack propagation. The synergistic effect of homogenization treatment and hot rolling process enables the alloy to have excellent fatigue resistance while ensuring high-temperature strength, thereby demonstrating longer service life and higher reliability in high-temperature cyclic stress environment.

[0019] Furthermore, the process of the solution treatment in step S3 is as follows: heating the rolled plate to 1080-1095° C. at a heating rate of 10-15° C. / min for 120-150 min, followed by water quenching to obtain a solution plate.

[0020] Furthermore, the aging treatment process in step S3 is as follows: heating the obtained solution plate to 790-800° C., heating at a heating rate of 5-10° C. / min, holding the plate for 120-150 min, and then water quenching to obtain the aged plate.

[0021] Furthermore, the stabilization treatment process in step S3 is as follows: heating the aging plate to 720-740° C. at a heating rate of 5-10° C. / min, keeping the temperature for 18-24 hours, and then air cooling to room temperature.

[0022] The present invention adopts the design of solution treatment, aging treatment and stabilization treatment, which is mainly used to enhance the high-temperature fatigue resistance of 901 high-temperature alloy. Through solution treatment, the Ni3(Ti,Al) precipitation phase and other secondary phases inside the alloy are fully dissolved, while the matrix composition is homogenized, the structural segregation is reduced, the grain structure of the γ phase is optimized, and a good structural foundation is laid for subsequent heat treatment. An appropriate heating rate and holding time are adopted to ensure that the alloy elements are fully diffused at high temperatures, and rapid cooling is carried out through water quenching to effectively fix the structure after solid solution, thereby improving the plasticity and toughness of the material and providing sufficient solute element reserves for precipitation strengthening. In the subsequent aging treatment process, the material is heated and kept warm within a specific temperature range, so that the Ni3(Ti,Al) precipitation phase is precipitated in an orderly manner and evenly distributed in the matrix in the form of a dispersed distribution, thereby enhancing the precipitation strengthening effect of the material and significantly improving the fatigue resistance. The water quenching treatment further fixes the distribution state of the precipitated phase, ensuring that the material maintains a stable strengthening effect under high temperature conditions. Finally, stabilization treatment further homogenizes the precipitates formed during aging, eliminates residual stress, optimizes the grain boundary structure, and reduces stress concentration in the structure caused by heat treatment, thereby improving high-temperature fatigue life. The synergistic effect of solution treatment, aging treatment, and stabilization treatment gives the alloy excellent fatigue resistance under high-temperature service conditions while maintaining good structural stability, ensuring that the material can maintain excellent mechanical properties and reliability under long-term cyclic loading.

[0023] Furthermore, the process of plasma nitriding treatment in step S4 is as follows: placing the heat-treated plate in step S3 in a nitriding furnace, evacuating the furnace to a vacuum degree of less than 6 Pa, introducing a mixed atmosphere of argon and hydrogen into the furnace, wherein the volume ratio of the mixed atmosphere of argon and hydrogen is 1:(3-5), and the gas pressure is controlled to be 50-100 Pa. The main cathode and the auxiliary cathode are turned on, a bias voltage of -1000 V is applied, and sputter cleaning is performed at a power of 2-5 kW for a cleaning time of 45-60 min. After the sputter cleaning is completed, the main cathode is closed, ammonia is introduced into the furnace to make the gas pressure reach 150-200 Pa, and the temperature is increased to 460-600° C. at a heating rate of 5-10° C. / min through the nitriding auxiliary cathode; then the main cathode is restarted for nitriding treatment, and the nitriding time is 20-60 h, and the auxiliary cathode operates at a duty cycle of 10-50%. After the nitriding is completed, the power is turned off and the furnace is slowly cooled to room temperature at a cooling rate of 2-5° C. / min in an ammonia atmosphere.

[0024] The present invention adopts the design of plasma nitriding treatment mainly for enhancing the high-temperature fatigue resistance of 901 high-temperature alloy. By establishing an environment below a specific vacuum degree in the nitriding furnace and introducing a mixed atmosphere of argon and hydrogen to optimize the surface activation conditions, the alloy surface can more evenly absorb active nitrogen atoms during the subsequent nitriding process. In the sputtering cleaning stage, the synergistic effect of the main cathode and the auxiliary cathode is utilized to remove the surface oxide layer and contaminants through high-energy ion bombardment under the condition of applying a bias voltage, thereby improving the uniformity and adhesion of the nitrided layer. Subsequently, by introducing ammonia gas and gradually raising the temperature to the target temperature, the nitrogen element is diffused into the surface layer of the alloy under the action of the auxiliary cathode, and the nitriding process is completed under the continuous action of the main cathode. The nitriding time and the duty cycle control of the auxiliary cathode ensure that the nitrogen atoms are fully diffused and stably combined on the surface of the alloy, so that a nitrided layer with high hardness is formed on the surface, thereby improving the wear resistance and fatigue crack initiation resistance of the material. Furthermore, slow cooling in an ammonia atmosphere effectively releases residual stress within the nitrided layer, reducing crack sensitivity caused by rapid cooling, thereby further improving the alloy's fatigue life under high-temperature alternating loads. The coordinated process parameters of the plasma nitriding treatment optimize surface strengthening while maintaining matrix toughness. This results in superior resistance to crack initiation and propagation in high-temperature fatigue environments, significantly enhancing the material's overall service performance.

[0025] The present invention also discloses a high-temperature fatigue-resistant material of a 901 high-temperature alloy, wherein the 901 high-temperature alloy is prepared by the above-mentioned preparation method;

[0026] The 901 high temperature alloy comprises a substrate and a nitriding layer on the surface of the substrate;

[0027] The matrix includes γ phase, Ni3(Ti,Al) precipitation phase, and MC type carbide;

[0028] The average grain size of the γ phase is 15 to 27 μm;

[0029] The interface between the γ phase and the Ni3(Ti,Al) precipitated phase is a semi-coherent interface;

[0030] The Ni3(Ti,Al) precipitated phase is uniformly dispersed in the γ matrix phase, with an average size of 50 to 200 nm and a volume fraction of 20 to 25%;

[0031] The MC type carbide includes TiC and NbC, and is precipitated along the grain boundaries in the form of coarse particles; the volume fraction of the MC type carbide is 2.0 to 4.0%, and the average diameter is 100 to 250 nm;

[0032] The thickness of the nitriding layer is 35-60 μm; the nitriding layer contains CrN, gamma-FeNi and Ni4N.

[0033] This invention utilizes the synergistic effects of optimized alloy composition design, precisely controlled heat treatment processes, and plasma nitriding technology to enhance the high-temperature fatigue resistance of 901 superalloy. By refining the γ-phase grains, uniformly dispersing the Ni3(Ti,Al) precipitates, and rationally controlling the volume fraction and distribution morphology of MC-type carbides, the alloy exhibits excellent resistance to fatigue crack initiation under high-temperature alternating loads. Precipitation phases at semi-coherent interfaces provide precipitation strengthening, ensuring a balance between high-temperature strength and ductility, while TiC and NbC precipitated along grain boundaries effectively inhibit grain boundary sliding, enhancing creep resistance while also avoiding fatigue crack susceptibility caused by excessive carbides. Furthermore, the plasma nitriding process forms a nitrided layer containing CrN, γ-FeNi, and Ni4N on the substrate surface, enhancing surface hardness, wear resistance, and crack initiation resistance while maintaining a certain level of toughness to ensure long-term service stability. The synergistic effect of matrix microstructure optimization and surface strengthening enables the alloy to exhibit excellent resistance to crack initiation and propagation under high-temperature fatigue conditions, thereby extending its overall service life.

[0034] (3) Beneficial technical effects

[0035] 1. This invention significantly improves the high-temperature fatigue resistance of 901 superalloy by optimizing alloy composition, smelting and refining, hot working, and the coordinated design of surface strengthening technologies. Compared with existing technologies, this invention offers significant advantages in terms of structural uniformity, fatigue crack initiation resistance, and long-term service stability. Through vacuum induction melting and electroslag remelting, the alloy's purity and uniformity are improved, reducing casting defects. Homogenization and hot rolling optimize the distribution of γ-phase and Ni3(Ti,Al) precipitation phases, enhancing matrix strengthening. Solution treatment, aging, and stabilization precisely control the morphology of precipitation phases, enhancing precipitation strengthening and reducing residual stress. Plasma nitriding forms a high-hardness nitrided layer on the surface, improving wear resistance and crack propagation resistance. The coordinated efforts of these process steps ensure that the alloy maintains excellent mechanical properties and reliability under high-temperature cyclic loading conditions, meeting the demanding service requirements of high-temperature structural components such as aircraft engines and gas turbines, and providing a new technical path for the research, development, and application of superalloy materials.

[0036] 2. The present invention significantly improves the high-temperature fatigue resistance of 901 high-temperature alloy by optimizing the synergistic effect of alloy composition, heat treatment process and surface nitriding technology. Compared with the existing technology, the present invention has obvious advantages in terms of organizational uniformity, crack initiation resistance and long-term service stability. By refining the γ phase grains, uniformly distributing the Ni3 (Ti, Al) precipitation phase, and rationally controlling the MC type carbide, the material has better fatigue resistance under high-temperature alternating loads. Plasma nitriding technology forms a high-hardness nitrided layer on the surface, which improves wear resistance and crack propagation resistance, while maintaining toughness to ensure long-term and stable service. The various components work together to enable the alloy to exhibit excellent fatigue resistance in high-temperature environments such as aircraft engines and gas turbines, extending service life and improving safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is the XRD phase analysis spectrum of the 901 high-temperature alloy prepared in Example 1 of the present invention.

[0038] Figure 2 This is the interface between the γ phase and the Ni3(Ti,Al) precipitation phase prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0039] To make the objectives, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0040] Example 1

[0041] A method for preparing a high-temperature fatigue-resistant material of a 901 high-temperature alloy comprises the following steps:

[0042] S1. Raw material proportioning and smelting: The raw materials of the high-temperature alloy are placed in a vacuum induction melting furnace for smelting. After smelting, they are rapidly cast to obtain a cast ingot. The cast ingot is then placed in an electroslag remelting furnace using the cast ingot as an electrode for electroslag remelting. After completion, an electroslag remelted ingot is obtained. The raw materials of the high-temperature alloy include, by weight percentage, 41.0% Ni, 11.0% Cr, 5.0% Mo, 2.2% Ti, 0.30% Al, 0.20% Si, 0.50% Mn, 0.40% Co, 0.02% C, 0.015% B, ≤0.001% S, ≤0.001% P, with the remainder being Fe and unavoidable impurities. The smelting process is as follows: at 10 -3 Pa, heated to 1500℃ at a heating rate of 5℃ / min and kept warm for 30min. During the holding period, the stirring rate was controlled at 10rpm. The electroslag remelting process was as follows: using CaO-Al2O3-MgO slag system as refining agent, remelting was carried out under the conditions of 30V and 500A. During the smelting process, the cooling water temperature was kept at 20℃ to ensure uniform cooling of the ingot.

[0043] S2. Homogenization and hot rolling: The electroslag remelting ingot from step S1 is placed in a muffle furnace and subjected to homogenization and hot rolling treatments in sequence to obtain a rolled plate; the homogenization and hot rolling process is as follows: heating to 1160°C at a heating rate of 5°C / min and keeping the temperature for 120 minutes, then cooling to 1100°C at a cooling rate of 10°C / min and hot rolling, with the deformation of a single rolling pass controlled at 10% and the total deformation at 50%, and slowly cooling to room temperature after rolling is completed.

[0044] S3. Three-step heat treatment: The plate after rolling in step S2 is subjected to solution treatment, aging treatment and stabilization treatment in sequence to obtain a heat-treated plate; the process of solution treatment is as follows: the rolled plate is heated to 1080℃, heated at a heating rate of 10℃ / min, and kept at this temperature for 120min, and then water quenched to obtain a solution plate. The process of aging treatment is as follows: the obtained solution plate is heated to 790℃, heated at a heating rate of 5℃ / min, and kept at this temperature for 120min, and then water quenched to obtain an aged plate. The process of stabilization treatment is as follows: the aged plate is heated to 720℃, heated at a heating rate of 5℃ / min, and kept at this temperature for 18h, and then air-cooled to room temperature.

[0045] S4. Machining and surface treatment: The plate heat-treated in step S3 is first machined, and then subjected to plasma nitriding treatment, and finally a high-temperature fatigue-resistant material of 901 high-temperature alloy is obtained; the process of plasma nitriding treatment is as follows: the plate heat-treated in step S3 is placed in a nitriding furnace, the furnace chamber is evacuated to a vacuum degree below 6Pa, and a mixed atmosphere of argon and hydrogen is introduced into the furnace, the volume ratio of the mixed atmosphere argon and hydrogen is 1:3, the gas pressure is controlled to 50Pa, the main cathode and the auxiliary cathode are turned on, and a bias voltage is applied. The voltage is -1000V and sputter cleaning is performed at a power of 2kW for 45 minutes. After the sputter cleaning is completed, the main cathode is turned off and ammonia is introduced into the furnace to make the gas pressure reach 150Pa. The auxiliary cathode is nitrided and the temperature is increased to 460°C at a heating rate of 5°C / min. The main cathode is then restarted for nitridation treatment. The nitriding time is 20 hours and the auxiliary cathode operates at a duty cycle of 10%. After the nitriding is completed, the power is turned off and the furnace is slowly cooled to room temperature at a cooling rate of 2°C / min in an ammonia atmosphere.

[0046] This embodiment provides a high-temperature fatigue-resistant material made of a 901 high-temperature alloy, comprising a matrix and a nitrided layer on the surface of the matrix. The matrix comprises a γ phase, a Ni3(Ti,Al) precipitate phase, and MC carbides. The average grain size of the γ phase is 27 μm, and the interface between the γ phase and the Ni3(Ti,Al) precipitate phase is a semi-coherent interface. The Ni3(Ti,Al) precipitate phase is uniformly dispersed in the γ matrix phase, with an average size of 50 nm and a volume fraction of 20%. MC carbides comprise TiC and NbC, precipitating along grain boundaries in the form of coarse particles. The volume fraction of MC carbides is 4.0%, and the average diameter is 100 nm. The nitrided layer is 35 μm thick and contains CrN, γ-FeNi, and Ni4N.

[0047] Depend on Figure 1 The XRD phase analysis results shown in the figure show that the 901 high-temperature alloy prepared in Example 1 of the present invention is mainly composed of γ phase (Fe-Ni based solid solution) and Ni3(Ti,Al) precipitation phase (γ' phase), among which the characteristic diffraction peak of γ' phase is clearly visible, indicating that it has been successfully precipitated in the alloy and has good structural integrity. Figure 2 It can be observed that the interface between the γ phase and the Ni3(Ti,Al) precipitate phase is clear, and no obvious interface defects or discontinuities are observed, indicating that the precipitate phase is well bonded to the matrix.

[0048] Example 2

[0049] A method for preparing a high-temperature fatigue-resistant material of a 901 high-temperature alloy comprises the following steps:

[0050] S1. Raw material proportioning and smelting: The raw materials of the high-temperature alloy are placed in a vacuum induction melting furnace for smelting. After smelting, they are rapidly cast to obtain a cast ingot. The cast ingot is then placed in an electroslag remelting furnace using the cast ingot as an electrode for electroslag remelting. After completion, an electroslag remelting ingot is obtained. The raw materials of the high-temperature alloy include, by weight percentage, 41.4% Ni, 11.6% Cr, 5.2% Mo, 2.3% Ti, 0.33% Al, 0.24% Si, 0.56% Mn, 0.43% Co, 0.04% C, 0.018% B, ≤0.001% S, ≤0.001% P, with the remainder being Fe and unavoidable impurities. The smelting process is as follows: at 10 -3 Pa, heated to 1515 ° C at a heating rate of 6 ° C / min and kept warm for 39 minutes. During the holding period, the stirring rate was controlled at 13 rpm. The electroslag remelting process was as follows: using CaO-Al2O3-MgO slag system as a refining agent, remelting was carried out under the conditions of 31V, 635A. During the smelting process, the cooling water temperature was maintained at 23 ° C to ensure uniform cooling of the ingot.

[0051] S2. Homogenization and hot rolling: The electroslag remelting ingot from step S1 is placed in a muffle furnace and subjected to homogenization and hot rolling treatments in sequence to obtain a rolled plate; the homogenization and hot rolling process is as follows: heating to 1170°C at a heating rate of 6°C / min and keeping warm for 144 minutes, then cooling to 1115°C at a cooling rate of 11°C / min and hot rolling, with the deformation of a single rolling pass controlled at 13% and the total deformation at 56%. After rolling, the plate is slowly cooled to room temperature.

[0052] S3. Three-step heat treatment: The plate after rolling in step S2 is subjected to solution treatment, aging treatment and stabilization treatment in sequence to obtain a heat-treated plate; the process of solution treatment is as follows: the rolled plate is heated to 1085℃, heated at a heating rate of 12℃ / min, and kept at this temperature for 129min, and then water quenched to obtain a solution plate. The process of aging treatment is as follows: the obtained solution plate is heated to 793℃, heated at a heating rate of 7℃ / min, and kept at this temperature for 129min, and then water quenched to obtain an aged plate. The process of stabilization treatment is as follows: the aged plate is heated to 727℃, heated at a heating rate of 7℃ / min, and kept at this temperature for 20h, and then air-cooled to room temperature.

[0053] S4. Machining and surface treatment: The plate heat-treated in step S3 is first machined, and then subjected to plasma nitriding treatment, and finally a high-temperature fatigue-resistant material of 901 high-temperature alloy is obtained; the process of plasma nitriding treatment is as follows: the plate heat-treated in step S3 is placed in a nitriding furnace, the furnace chamber is evacuated to a vacuum degree below 6Pa, and a mixed atmosphere of argon and hydrogen is introduced into the furnace, the volume ratio of the mixed atmosphere argon and hydrogen is 1:4, the gas pressure is controlled to 65Pa, the main cathode and the auxiliary cathode are turned on, and a bias voltage is applied. The voltage is -1000V and sputter cleaning is performed at a power of 3kW for 48 minutes. After the sputter cleaning is completed, the main cathode is turned off and ammonia is introduced into the furnace to make the gas pressure reach 165Pa. The auxiliary cathode is nitrided and the temperature is raised to 493°C at a heating rate of 7°C / min. The main cathode is then restarted for nitridation treatment. The nitriding time is 32 hours and the auxiliary cathode operates at a duty cycle of 22%. After the nitriding is completed, the power is turned off and the furnace is slowly cooled to room temperature at a cooling rate of 3°C / min in an ammonia atmosphere.

[0054] This embodiment discloses a high-temperature fatigue-resistant material made of a 901 high-temperature alloy, comprising a matrix and a nitrided layer on the surface of the matrix. The matrix comprises a γ phase, Ni3(Ti,Al) precipitates, and MC carbides. The average grain size of the γ phase is 24 μm, and the interface between the γ phase and the Ni3(Ti,Al) precipitates is a semi-coherent interface. The Ni3(Ti,Al) precipitates are uniformly dispersed within the γ matrix phase, with an average grain size of 110 nm and a volume fraction of 22%. MC carbides comprise TiC and NbC, precipitating along grain boundaries in the form of coarse particles. The volume fraction of MC carbides is 3.5%, and the average diameter is 160 nm. The nitrided layer is 44 μm thick and contains CrN, γ-FeNi, and Ni4N. By controlling the size and volume fraction of the precipitates through a moderate heat treatment process, this embodiment ensures high-temperature strength while also achieving good fatigue resistance and balanced toughness. This material is suitable for high-temperature alternating load environments with moderate stress levels.

[0055] Example 3

[0056] A method for preparing a high-temperature fatigue-resistant material of a 901 high-temperature alloy comprises the following steps:

[0057] S1. Raw material proportioning and smelting: The raw materials of the high-temperature alloy are placed in a vacuum induction melting furnace for smelting. After smelting, they are rapidly cast to obtain a cast ingot. The cast ingot is then placed in an electroslag remelting furnace using the cast ingot as an electrode for electroslag remelting. After completion, an electroslag remelting ingot is obtained. The raw materials of the high-temperature alloy include, by weight percentage, 41.9% Ni, 12.2% Cr, 5.5% Mo, 2.4% Ti, 0.37% Al, 0.29% Si, 0.61% Mn, 0.47% Co, 0.06% C, 0.021% B, ≤0.001% S, ≤0.001% P, with the remainder being Fe and unavoidable impurities. The smelting process is as follows: at 10 -3 Pa vacuum environment, heated to 1530 ° C at a heating rate of 8 ° C / min, and kept warm for 48 minutes. During the holding period, the stirring rate was controlled at 16 rpm. The electroslag remelting process was as follows: using CaO-Al2O3-MgO slag system as a refining agent, remelting was carried out under the conditions of 33V, 710A. During the smelting process, the cooling water temperature was maintained at 26 ° C to ensure uniform cooling of the ingot.

[0058] S2. Homogenization and hot rolling: The electroslag remelting ingot from step S1 is placed in a muffle furnace and subjected to homogenization and hot rolling treatments in sequence to obtain a rolled plate; the homogenization and hot rolling process is as follows: heating to 1176°C at a heating rate of 8°C / min and keeping the temperature for 168 minutes, then cooling to 1125°C at a cooling rate of 12°C / min and hot rolling. The deformation of a single rolling pass is controlled at 16%, and the total deformation is 63%. After rolling is completed, the plate is slowly cooled to room temperature.

[0059] S3. Three-step heat treatment: The plate after rolling in step S2 is subjected to solution treatment, aging treatment and stabilization treatment in sequence to obtain a heat-treated plate; the process of solution treatment is as follows: the rolled plate is heated to 1090℃, heated at a heating rate of 14℃ / min, and kept at this temperature for 138min, and then water quenched to obtain a solution plate. The process of aging treatment is as follows: the obtained solution plate is heated to 797℃, heated at a heating rate of 9℃ / min, and kept at this temperature for 138min, and then water quenched to obtain an aged plate. The process of stabilization treatment is as follows: the aged plate is heated to 733℃, heated at a heating rate of 9℃ / min, and kept at this temperature for 22h, and then air-cooled to room temperature.

[0060] S4. Machining and surface treatment: The plate heat-treated in step S3 is first machined, and then subjected to plasma nitriding treatment, and finally a high-temperature fatigue-resistant material of 901 high-temperature alloy is obtained; the process of plasma nitriding treatment is as follows: the plate heat-treated in step S3 is placed in a nitriding furnace, the furnace chamber is evacuated to a vacuum degree below 6Pa, and a mixed atmosphere of argon and hydrogen is introduced into the furnace, the volume ratio of the mixed atmosphere argon and hydrogen is 1:5, the gas pressure is controlled to 80Pa, the main cathode and the auxiliary cathode are turned on, and a bias voltage is applied. The voltage is -1000V and sputter cleaning is performed at a power of 4kW for 54 minutes. After the sputter cleaning is completed, the main cathode is turned off and ammonia is introduced into the furnace to make the gas pressure reach 180Pa. The auxiliary cathode is nitrided and the temperature is raised to 527°C at a heating rate of 9°C / min. The main cathode is then restarted for nitridation treatment. The nitriding time is 44 hours and the auxiliary cathode operates at a duty cycle of 36%. After the nitriding is completed, the power is turned off and the furnace is slowly cooled to room temperature at a cooling rate of 4°C / min in an ammonia atmosphere.

[0061] This embodiment provides a high-temperature fatigue-resistant material of a 901 high-temperature alloy, comprising a matrix and a nitrided layer on the surface of the matrix. The matrix comprises a γ phase, a Ni3(Ti,Al) precipitate phase, and MC carbides. The average grain size of the γ phase is 18 μm, and the interface between the γ phase and the Ni3(Ti,Al) precipitate phase is a semi-coherent interface. The Ni3(Ti,Al) precipitate phase is uniformly dispersed in the γ matrix phase, with an average size of 160 nm and a volume fraction of 23.5%. MC carbides comprise TiC and NbC, precipitating along grain boundaries in the form of coarse particles. The volume fraction of MC carbides is 3.1%, and the average diameter is 210 nm. The nitrided layer is 52 μm thick and contains CrN, γ-FeNi, and Ni4N.

[0062] Example 4

[0063] A method for preparing a high-temperature fatigue-resistant material of a 901 high-temperature alloy comprises the following steps:

[0064] S1. Raw material proportioning and smelting: The raw materials of the high-temperature alloy are placed in a vacuum induction melting furnace for smelting. After smelting, they are rapidly cast to obtain a cast ingot. The cast ingot is then placed in an electroslag remelting furnace using the cast ingot as an electrode for electroslag remelting. After completion, an electroslag remelting ingot is obtained. The raw materials of the high-temperature alloy include, by weight percentage, 42.5% Ni, 13.0% Cr, 5.8% Mo, 2.5% Ti, 0.40% Al, 0.35% Si, 0.65% Mn, 0.50% Co, 0.09% C, 0.025% B, ≤0.001% S, ≤0.001% P, with the remainder being Fe and unavoidable impurities. The smelting process is as follows: at 10 -3Pa, heated to 1550℃ at a heating rate of 10℃ / min and kept warm for 60min. During the holding period, the stirring rate was controlled at 20rpm. The electroslag remelting process was as follows: using CaO-Al2O3-MgO slag system as refining agent, remelting was carried out under the conditions of 35V and 800A. During the smelting process, the cooling water temperature was kept at 30℃ to ensure uniform cooling of the ingot.

[0065] S2. Homogenization and hot rolling: The electroslag remelting ingot from step S1 is placed in a muffle furnace and subjected to homogenization and hot rolling treatments in sequence to obtain a rolled plate; the homogenization and hot rolling process is as follows: heating to 1180°C at a heating rate of 10°C / min and keeping warm for 180 minutes, then cooling to 1150°C at a cooling rate of 15°C / min and hot rolling, with the deformation of a single rolling pass controlled at 20% and the total deformation at 70%. After rolling is completed, the plate is slowly cooled to room temperature.

[0066] S3. Three-step heat treatment: The plate after rolling in step S2 is subjected to solution treatment, aging treatment and stabilization treatment in sequence to obtain a heat-treated plate; the process of solution treatment is as follows: the rolled plate is heated to 1095°C, heated at a heating rate of 15°C / min, and kept at this temperature for 150 minutes, and then water quenched to obtain a solution plate. The process of aging treatment is as follows: the obtained solution plate is heated to 800°C, heated at a heating rate of 10°C / min, and kept at this temperature for 150 minutes, and then water quenched to obtain an aged plate. The process of stabilization treatment is as follows: the aged plate is heated to 740°C, heated at a heating rate of 10°C / min, and kept at this temperature for 24 hours, and then air-cooled to room temperature.

[0067] S4. Machining and surface treatment: The plate heat-treated in step S3 is first machined, and then subjected to plasma nitriding treatment, and finally a high-temperature fatigue-resistant material of 901 high-temperature alloy is obtained; the process of plasma nitriding treatment is as follows: the heat-treated plate in step S3 is placed in a nitriding furnace, the furnace chamber is evacuated to a vacuum degree below 6Pa, a mixed atmosphere of argon and hydrogen is introduced into the furnace, the volume ratio of the mixed atmosphere argon and hydrogen is 1:5, the gas pressure is controlled to 100Pa, the main cathode and the auxiliary cathode are turned on, and a bias voltage is applied. The voltage is -1000V, and sputter cleaning is performed at a power of 5kW for 60 minutes. After the sputter cleaning is completed, the main cathode is turned off, and ammonia is introduced into the furnace to make the gas pressure reach 200Pa, and the auxiliary cathode is nitrided to increase the temperature to 600°C at a heating rate of 10°C / min; then the main cathode is restarted for nitridation treatment, and the nitriding time is 60 hours. The auxiliary cathode works at a duty cycle of 50%. After the nitriding is completed, the power is turned off and the furnace is slowly cooled to room temperature at a cooling rate of 5°C / min in an ammonia atmosphere.

[0068] This embodiment provides a high-temperature fatigue-resistant material made of a 901 high-temperature alloy, comprising a matrix and a nitrided layer on the surface of the matrix. The matrix comprises a γ phase, a Ni3(Ti,Al) precipitate phase, and MC carbides. The average grain size of the γ phase is 15 μm, and the interface between the γ phase and the Ni3(Ti,Al) precipitate phase is a semi-coherent interface. The Ni3(Ti,Al) precipitate phase is uniformly dispersed in the γ matrix phase, with an average size of 200 nm and a volume fraction of 25%. MC carbides comprise TiC and NbC, precipitating along grain boundaries in the form of coarse particles. The volume fraction of MC carbides is 2.0%, and the average diameter is 250 nm. The nitrided layer is 60 μm thick and contains CrN, γ-FeNi, and Ni4N.

[0069] Comparative Example 1

[0070] It is basically the same as Example 1, except that the electroslag remelting step is removed.

[0071] Comparative Example 2

[0072] It is basically the same as Example 1, except that the solution temperature is set to 1120°C (higher than the specified range of 1095°C).

[0073] Comparative Example 3

[0074] It is basically the same as Example 1, except that the solution temperature is set to 1060°C (lower than the specified range of 1080°C).

[0075] Comparative Example 4

[0076] The method is basically the same as Example 1, except that the total rolling deformation is set to 40% (lower than the specified range of 50-70%).

[0077] Comparative Example 5

[0078] It is basically the same as Example 1, except that the stabilization process is canceled.

[0079] Comparative Example 6

[0080] It is basically the same as Example 1, except that the plasma nitriding step is removed.

[0081] Comparative Example 7

[0082] It is basically the same as Example 1, except that the solution temperature is set to 1060°C (lower than the specified range of 1080°C).

[0083] Comparative Example 8

[0084] It is basically the same as Example 1, except that the nitriding temperature is set to 650°C (higher than the specified range of 600°C).

[0085] Performance testing:

[0086] For the high-temperature fatigue performance, specimens (Ra ≤ 0.2 μm) were prepared using a high-temperature servo fatigue testing machine in accordance with ASTM E466 or ISO 12106 standards. Symmetric cycling (R = -1) or tension-tension loading (0 < R < 1) was ensured at a constant temperature of 650 °C (fluctuation ≤ ±2 °C), with a frequency of 5 Hz and a maximum stress of 50% - 80% of the yield strength. The fatigue life (Nf) was recorded to evaluate the influence of different processes on the high-temperature fatigue performance.

[0087] The properties of the superalloys in Examples 1 - 4 and Comparative Examples 1 - 8 are summarized in Table 1.

[0088] Table 1 Summary of the properties of the superalloys in Examples 1 - 4 and Comparative Examples 1 - 8

[0089]

[0090] In the comparative experiments, the changes in different process parameters had a significant impact on the material properties. Removing electroslag remelting led to an impure structure, resulting in a decrease in fatigue life, and at the same time, the tensile strength, yield strength, and plasticity all decreased. Deviating from the solution temperature also affected the material properties. Among them, too high solution temperature led to coarse grains, causing a decrease in fatigue life, tensile strength, yield strength, and plasticity, while too low solution temperature led to insufficient solution and insufficient precipitation strengthening, thus reducing the fatigue life and strength. In addition, insufficient rolling deformation led to coarse structure, resulting in the most obvious decrease in strength and plasticity, and at the same time, the fatigue life decreased significantly. Canceling the stabilization treatment also weakened the precipitation strengthening effect, resulting in a decrease in fatigue life, strength, and plasticity. Removing plasma nitriding had little effect on other properties, but the surface hardness decreased significantly. Although too high nitriding temperature increased the surface hardness, it significantly reduced the fatigue life, and at the same time, the strength and plasticity also decreased. In summary, reasonable control of each process parameter is crucial for optimizing the material properties.

[0091] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the above examples, those of ordinary skill in the art should understand that any equivalent structural transformation made under the concept of the present invention using the content of the specification and drawings of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a high-temperature fatigue-resistant material of a 901 high-temperature alloy, characterized in that: The following steps are involved: S1. Raw Material Proportioning and Melting: The high-temperature alloy raw materials are placed in a vacuum induction melting furnace for melting. After melting, they are rapidly cast to obtain a cast ingot. The cast ingot is then placed in an electroslag remelting furnace for electroslag remelting, using the cast ingot as an electrode. S2 homogenization and hot rolling: The electroslag remelting ingot of step S1 is placed in a muffle furnace, followed by homogenization and hot rolling to obtain a rolled plate; S3 three-step heat treatment: the plate after step S2 rolling is sequentially subjected to solution treatment, aging treatment and stabilization treatment to obtain a heat-treated plate; S4 machining and surface treatment: The plate after heat treatment in step S3 is first machined, and then subjected to plasma nitriding treatment, and finally a high-temperature fatigue-resistant material of 901 high-temperature alloy is obtained; The raw materials of the high-temperature alloy in step S1 include, by weight percentage, 41.0-42.5% Ni, 11.0-13.0% Cr, 5.0-5.8% Mo, 2.2-2.5% Ti, 0.30-0.40% Al, 0.20-0.35% Si, 0.50-0.65% Mn, 0.40-0.50% Co, 0.02-0.09% C, 0.015-0.025% B, ≤0.001% S, ≤0.001% P, and the balance being Fe and unavoidable impurities; The homogenization and hot rolling process of step S2 is as follows: heating to 1160-1180°C at a heating rate of 5-10°C / min and holding the temperature for 120-180min, then cooling to 1100-1150°C at a cooling rate of 10-15°C / min, and hot rolling, wherein the deformation of a single rolling pass is controlled at 10-20%, and the total deformation is 50-70%, and slowly cooling to room temperature after rolling is completed; The process of the solution treatment in step S3 is as follows: heating the rolled plate to 1080-1095°C at a heating rate of 10-15°C / min for 120-150 min, and then water quenching to obtain a solution plate; The aging treatment process in step S3 is as follows: heating the obtained solutionized plate to 790-800°C, heating at a heating rate of 5-10°C / min, holding the plate for 120-150 minutes, and then water quenching to obtain an aged plate; The stabilization treatment process in step S3 is as follows: heating the aging plate to 720-740°C at a heating rate of 5-10°C / min for 18-24 hours, and then air cooling to room temperature; The plasma nitriding treatment process in step S4 is as follows: placing the heat-treated plate in step S3 in a nitriding furnace, evacuating the furnace to a vacuum degree of less than 6 Pa, introducing a mixed atmosphere of argon and hydrogen into the furnace, wherein the volume ratio of the mixed atmosphere of argon and hydrogen is 1:(3-5), and the gas pressure is controlled to be 50-100 Pa. The main cathode and the auxiliary cathode are turned on, a bias voltage of −1000 V is applied, and sputter cleaning is performed at a power of 2-5 kW for a cleaning time of 45-60 min. After the sputter cleaning is completed, the main cathode is turned off, ammonia is introduced into the furnace to increase the gas pressure to 150-200 Pa, and the temperature is increased to 460-600°C at a heating rate of 5-10°C / min through the nitriding auxiliary cathode; then the main cathode is restarted for nitriding treatment, and the nitriding time is 20-60 h. The auxiliary cathode operates at a duty cycle of 10-50%. After the nitriding is completed, the power is turned off, and the plate is slowly cooled to room temperature in an ammonia atmosphere at a cooling rate of 2-5°C / min.

2. The method for preparing a high-temperature fatigue-resistant material of a 901 high-temperature alloy according to claim 1, characterized in that: The smelting process in step S1 is as follows: heating to 1500-1550°C at a heating rate of 5-10°C / min under a vacuum environment of 10⁻³ Pa, and keeping the temperature for 30-60 min, with the stirring rate controlled at 10-20 rpm during the holding period.

3. The method for preparing a high-temperature fatigue-resistant material of a 901 high-temperature alloy according to claim 1, characterized in that: The electroslag remelting process in step S1 is as follows: using CaO-Al2O3-MgO slag system as a refining agent, remelting is performed under the conditions of 30-35 V and 500-800 A, and the cooling water temperature is maintained at 20-30°C during the smelting process to ensure uniform cooling of the ingot.

4. A high-temperature fatigue-resistant material of 901 high-temperature alloy, characterized in that: The high-temperature alloy is prepared by the preparation method according to any one of claims 1 to 3; The 901 high temperature alloy comprises a substrate and a nitriding layer on the surface of the substrate; The matrix includes γ phase, Ni3(Ti,Al) precipitation phase, and MC type carbide; The average grain size of the γ phase is 15-27 μm; The interface between the γ phase and the Ni3(Ti,Al) precipitation phase is a semi-coherent interface.

5. The high-temperature fatigue-resistant material of 901 high-temperature alloy according to claim 4, characterized in that: The Ni3(Ti,Al) precipitated phase is uniformly dispersed in the γ matrix phase, with an average size of 50-200 nm and a volume fraction of 20-25%; The MC type carbide includes TiC and NbC, and is precipitated along the grain boundary in the form of coarse particles; the volume fraction of the MC type carbide is 2.0-4.0%, and the average diameter is 100-250nm.

6. The high-temperature fatigue-resistant material of 901 high-temperature alloy according to claim 4, characterized in that: The thickness of the nitriding layer is 35-60 μm; the nitriding layer contains CrN, γ-FeNi and Ni4N.

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