A low-expansion nickel-based superalloy, a preparation method and application thereof

Abstract

The application discloses a low-expansion nickel-based superalloy and a preparation method and application thereof. The low-expansion nickel-based superalloy comprises the following components in percentage by mass: Fe: 6-10%, Cr: 12-20%, Mo: 6-12%, W: 0.2-0.8%, Ti: 1.8-2.4%, Al: 1.1-1.7%, C: 0.02-0.08%, B: 0.001-0.005%, Zr: 0.01-0.05%, Co: 1.7-2.3%, and the balance of Ni. The mass fraction of Ti and Al satisfies 1.4 < Ti / Al < 1.8. The alloy is composed of an austenite matrix (gamma phase), an intracrystalline strengthening phase Ni3(Al,Ti) (gamma' phase), a grain boundary strengthening phase M 23 The alloy has a low thermal expansion coefficient, excellent high-temperature strength and toughness, good structure and performance stability, and can be used for high-parameter ultra-supercritical power station turbine rotors, bolts, blades, valves and the like, and aero-engine cases and sealing rings and the like.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature alloy technology, specifically relating to a low-expansion nickel-based high-temperature alloy, its preparation method, and its application. Background Technology

[0002] High-temperature structural materials, represented by high-temperature alloys and intermetallic compounds, are key materials in the manufacture of hot-end components. Because the structure and operating conditions of these materials differ under high-temperature service conditions, ensuring their service life requires not only comprehensive performance requirements but also specific key performance characteristics. For example, high-temperature alloy tubing used in reheaters / superheaters of ultra-supercritical power plant boilers primarily needs excellent high-temperature creep resistance and oxidation / corrosion resistance; high-temperature alloys used in containers for molten fluoride salts in fourth-generation nuclear reactors (thorium-based molten salt reactors) primarily need good oxidation resistance to hot fluoride salts; and high-temperature alloys used in aero-engine combustion chambers primarily need excellent resistance to thermal fatigue. For high-parameter ultra-supercritical power plant turbine rotors, bolts, blades, valves, and aero-engine casings and sealing rings, which require approximately constant dimensions in certain high-temperature environments, in addition to requirements for strength, oxidation resistance, and corrosion resistance, they also need to have a low coefficient of thermal expansion to ensure minimal dimensional changes and internal stresses during service.

[0003] Currently, researchers primarily develop low-expansion alloys that meet the requirements of different temperatures through alloy composition optimization. Since the 1970s, foreign countries have developed Cr-free low-expansion alloys such as Inco1oy903 and Inco1oy907, which resulted in poor oxidation resistance. Subsequently, Cr-containing low-expansion alloys such as Inconel783 and Thermo-span were developed, significantly improving their oxidation resistance. However, the addition of Cr causes a substantial increase in the alloy's coefficient of thermal expansion with increasing temperature. Furthermore, high alloying leads to poor alloy processing formability and microstructural stability. Therefore, to meet the needs of modern aerospace and energy fields, developing alloys with low high-temperature coefficients of thermal expansion and high comprehensive performance has significant scientific and application value. Summary of the Invention

[0004] Therefore, the technical problem to be solved by this invention is to overcome the shortcomings of existing high-temperature alloys with low coefficients of thermal expansion and poor overall performance, thereby providing a low-expansion nickel-based high-temperature alloy, its preparation method, and its applications. The low-expansion nickel-based high-temperature alloy of this invention has a low coefficient of thermal expansion, while also possessing excellent high-temperature strength and toughness, good microstructure and performance stability. It can be used for components such as rotors, bolts, blades, and valves in high-parameter ultra-supercritical power plant turbines, as well as aero-engine casings and sealing rings.

[0005] To this end, the present invention provides the following technical solution.

[0006] In a first aspect, the present invention provides a low-expansion nickel-based superalloy comprising, by mass percentage: Fe: 6-10%, Cr: 12-20%, Mo: 6-12%, W: 0.2-0.8%, Ti: 1.8-2.4%, Al: 1.1-1.7%, C: 0.02-0.08%, B: 0.001-0.005%, Zr: 0.01-0.05%, Co: 1.7-2.3%, with the balance being Ni, wherein the mass fractions of Ti and Al satisfy: 1.4 < Ti / Al < 1.8.

[0007] Furthermore, the Fe content by mass percentage is 7-9%; the Co content by mass percentage is 1.8-2.2%.

[0008] Furthermore, the mass fractions of Ti and Al satisfy the following condition: 1.5 ≤ Ti / Al ≤ 1.7.

[0009] Furthermore, at least one of the following conditions must be met:

[0010] (1) The mass percentage content of Cr is 14-18%;

[0011] (2) The mass percentage content of Mo is 8-10%;

[0012] (3) The mass percentage content of W is 0.4% to 0.6%;

[0013] (4) The mass percentage content of Ti is 2.0-2.2%;

[0014] (5) The Al content is 1.3-1.5% by mass;

[0015] (6) The mass percentage content of C is 0.04-0.06%;

[0016] (7) The mass percentage content of B is 0.002 to 0.004%;

[0017] (8) The Zr content is 0.02% to 0.04% by mass.

[0018] Secondly, the present invention provides a method for preparing a low-expansion nickel-based superalloy, comprising the following steps:

[0019] Step 1: Melt the raw materials under vacuum and cast them into alloy ingots. Homogenize the alloy ingots at 1150-1200℃ for 10-20 hours and then air cool them to room temperature.

[0020] Step 2: Roll the homogenized alloy ingot at 150-200℃ above the γ′ phase precipitation temperature, with a deformation amount of 10-20% per pass, a deformation amount of more than 20% in the last pass, and a final total deformation amount of 40-60%.

[0021] Step 3: The rolled alloy is solution treated at 140-180℃ above the γ′ phase precipitation temperature for 1-2 hours, and then solution treated at 80-100℃ above the γ′ phase precipitation temperature for 1.5-2.5 hours.

[0022] Step 4: The solution-treated alloy is aged at 280-320℃ for 10-14 hours below the γ′ phase precipitation temperature, and then aged at 100-140℃ for 2-6 hours below the γ′ phase precipitation temperature to obtain a low-expansion nickel-based high-temperature alloy.

[0023] Furthermore, in step 2, after each rolling pass is completed, the material is returned to the furnace for heat preservation before proceeding to the next rolling pass.

[0024] Furthermore, in step 2, the temperature for each reheating is the same as the rolling temperature, and the reheating time is 10-20 minutes.

[0025] Furthermore, the obtained low-expansion nickel-based superalloy has an average grain size of 60-100 μm, an intragranular γ′ phase size of 20-40 nm, and continuously distributed M-phase at the grain boundaries. 23 C6 type carbides; the average coefficient of linear expansion of this alloy is less than 15 × 10⁻⁶ between 20-650℃. -6 / ℃; the yield strength of the alloy at 650℃ is not less than 600MPa and the elongation after fracture is not less than 35%; no harmful phases precipitate after the alloy is exposed to heat at 650℃ for 2300h.

[0026] Thirdly, the present invention provides the application of low-expansion nickel-based superalloys or low-expansion nickel-based superalloys prepared according to the method in thermal power units and aero engines.

[0027] The technical solution of this invention has the following advantages:

[0028] 1. The low-expansion nickel-based superalloy provided by the present invention comprises, by mass percentage: Fe: 6-10%, Cr: 12-20%, Mo: 6-12%, W: 0.2-0.8%, Ti: 1.8-2.4%, Al: 1.1-1.7%, C: 0.02-0.08%, B: 0.001-0.005%, Zr: 0.01-0.05%, Co: 1.7-2.3%, with the balance being Ni, where 1.4 < Ti / Al < 1.8.

[0029] The low-expansion nickel-based superalloy provided by this invention is based on the alloy design concept of precipitation strengthening, solid solution strengthening, and grain boundary strengthening.

[0030] As the main elements in the precipitation strengthening phase Ni3(Al,Ti)(γ′), appropriate amounts of Ti and Al ensure the volume fraction of the γ′ strengthening phase within the grains. Too low a total amount of Ti and Al will reduce the volume fraction of the γ′ strengthening phase, compromising the alloy's strength; too high a total amount will increase the coefficient of thermal expansion. A relatively high Ti / Al ratio increases the antiphase domain boundary energy, thus increasing strength, while also preventing the precipitation of harmful phases. However, an excessively high Ti / Al ratio reduces the stability of the γ′ phase at high temperatures, decreasing the alloy's high-temperature strength and hot workability. An excessively low Ti / Al ratio increases the tendency for harmful phases to precipitate within the grains, severely impairing the alloy's overall performance. Therefore, the Ti content should be controlled between 1.8% and 2.4%, the Al content between 1.1% and 1.7%, and the Ti / Al ratio between 1.4% and 1.8%.

[0031] While chromium (Cr) acts as a solid solution element to strengthen the alloy, it also works with Al to improve the alloy's oxidation and corrosion resistance, while preventing the formation of harmful phases. If the Cr content is too low, the alloy's oxidation resistance cannot be guaranteed. If the Cr content is too high, it will significantly increase the alloy's coefficient of thermal expansion and promote the precipitation of harmful phases, reducing the alloy's mechanical properties. Therefore, the Cr content in this invention is controlled at 12-20%.

[0032] As solid solution elements, W and Mo significantly promote the high-temperature performance of alloys and reduce their coefficient of thermal expansion. However, excessive W content increases segregation during alloy smelting, thereby reducing the alloy's hot workability. Excessive Mo content easily causes pitting corrosion and forms volatile oxides, impairing the alloy's oxidation resistance. Conversely, insufficient W and Mo content reduces the solid solution strengthening effect and increases the alloy's coefficient of thermal expansion. Therefore, in this invention, the W content is controlled at 0.2–0.8%, and the Mo content is controlled at 6–12%.

[0033] An appropriate amount of Fe is mainly used to replace Ni. Since Fe is relatively inexpensive, an appropriate amount of Fe can significantly improve the cost-effectiveness of the alloy, and Fe can also significantly improve the hot working properties of the alloy. However, excessive Fe content will reduce the corrosion resistance of the alloy, hinder the precipitation of the γ′ strengthening phase, and reduce the structural stability and high-temperature strength of the alloy. Therefore, the Fe content in this invention should be controlled at 6-10%.

[0034] For Ni3(Al,Ti)(γ′) phase-strengthened high-temperature alloys, the better the stability of the γ′ phase, the smaller the coefficient of thermal expansion. Therefore, adding γ′ phase stabilizing elements is also beneficial to reducing the coefficient of thermal expansion. An appropriate amount of Co can reduce the steady-state creep rate and increase the amount of the γ′ strengthening phase, thereby improving strength, and further ensuring good thermal stability of the γ′ strengthening phase within the service temperature range. Simultaneously, the combined addition of Co, W, and Mo ensures that the alloy has a low coefficient of thermal expansion. The Co content of this invention is controlled at 1.7–2.3%, which effectively controls costs while achieving the above-mentioned beneficial effects.

[0035] An appropriate amount of carbon element forms M at the grain boundary. 23 C6-type carbides strengthen grain boundaries, while appropriate amounts of B and Zr segregate to the grain boundaries, reducing grain boundary defects, increasing grain boundary bonding strength, and decreasing grain boundary diffusion rate, thereby further strengthening the grain boundaries. The synergistic effect of C, B, and Zr ensures that the grain boundaries have excellent high-temperature strength. However, when the C content is too high, the carbides (such as MC and M...)... 23 The mass fraction of C6-type carbides increases, making their morphology, size, and distribution difficult to control. Furthermore, they occupy alloy strengthening elements (such as Cr and Ti), reducing the intragranular strengthening effect. Therefore, the C content in this invention should be controlled between 0.02% and 0.08%. When the B content is too high, it will form a boride eutectic, damaging the alloy's processing and mechanical properties. Therefore, the B content in this invention should be controlled between 0.001% and 0.005%. When the Zr content is too high, it will accelerate the coarsening of the γ′ phase during service, thus resulting in a loss of mechanical properties. Therefore, the Zr content in this invention should be controlled between 0.01% and 0.05%.

[0036] The low-expansion nickel-based superalloy designed in this invention contains a low content of Co and an appropriate amount of Fe, with a suitable Ti / Al ratio. This alloy has a low coefficient of thermal expansion and, while ensuring low cost, exhibits excellent high-temperature strength and toughness, hot working performance, oxidation resistance, and good microstructure and performance stability.

[0037] The low-expansion nickel-based superalloy obtained by this invention has an average grain size of 60-100 μm, an intragranular γ′ phase size of 20-40 nm, and continuously distributed M-phase at the grain boundaries. 23 C6 type carbides; the average coefficient of linear expansion of this alloy is less than 15 × 10⁻⁶ between 20-650℃. -6 / ℃; the yield strength of the alloy at 650℃ is not less than 600MPa and the elongation after fracture is not less than 30%; no harmful phases precipitate after the alloy is exposed to heat at 650℃ for 2300h.

[0038] 2. The preparation method of the low-expansion nickel-based superalloy provided by this invention first employs a suitable homogenization temperature and time to ensure significant improvement in microstructure uniformity while maintaining economic efficiency. A simple rolling process is used, with rolling performed at 150-200°C above the γ′ phase precipitation temperature to ensure complete dissolution of the reinforcing γ′ phase, effectively reducing deformation resistance while controlling the driving force for grain growth. By combining reasonable rolling deformation and reflow time, coarse grains are broken down and recrystallized for refinement without significant grain growth. The final pass uses a large deformation to ensure the alloy has high energy storage and fine grain size, effectively controlling grain size. Then, a staged solution treatment is employed. First, the hot-deformed alloy is solution treated at 140-180°C above the γ′ phase precipitation temperature for 1-2 hours to further control the grain size to meet application requirements. Then, a solution treatment is performed at 80-100°C above the γ′ phase precipitation temperature for 1.5-2.5 hours to further control the carbide size and distribution, thereby improving creep resistance. Finally, a staged aging treatment was employed. First, the solution-treated alloy was aged at 280-320℃ below the γ′ phase precipitation temperature for 10-14 hours to control γ′ phase nucleation. Then, it was aged at 100-140℃ below the γ′ phase precipitation temperature for 2-6 hours to further control the γ′ phase particle diameter and volume fraction. The optimization of the alloy composition and preparation process resulted in a low coefficient of thermal expansion at 600-700℃, excellent high-temperature strength and toughness, and good microstructure and performance stability, making it suitable for manufacturing high-parameter ultra-supercritical power plant turbine bolts and blades, aero-engine casings, and sealing rings. Attached Figure Description

[0039] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0040] Figure 1 Grain characteristics of the low-expansion nickel-based superalloy prepared in Example 1;

[0041] Figure 2 The grain boundary M of the low-expansion nickel-based superalloy prepared in Example 1 23 C6 morphology;

[0042] Figure 3 The intragranular γ′ phase morphology of the low-expansion nickel-based superalloy prepared in Example 1;

[0043] Figure 4The microstructure of the low-expansion nickel-based superalloy prepared in Example 1 after heat exposure at 650°C for 2300 h is shown.

[0044] Figure 5 The microstructure of the low-expansion nickel-based superalloy prepared in Comparative Example 2 after heat exposure at 650℃ for 2300h is shown. Detailed Implementation

[0045] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0046] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0047] A method for preparing low-expansion nickel-based superalloys includes the following steps:

[0048] Step 1: Melt the raw materials under vacuum and cast them into alloy ingots. Then, homogenize the alloy ingots at 1150-1200℃ for 10-20 hours and air cool them to room temperature.

[0049] Table 1 Chemical composition (wt%)

[0050] Fe Cr Mo W Ti Al C B Zr Co Ni Example 1 9 16 9 0.5 2.1 1.4 0.05 0.003 0.02 2.0 Bal. Example 2 7 14 8 0.4 2.4 1.6 0.06 0.004 0.03 2.1 Bal. Example 3 8 17 10 0.6 2.2 1.3 0.07 0.002 0.02 1.9 Bal. Example 4 7 13 11 0.5 2.3 1.5 0.04 0.005 0.04 2.2 Bal.

[0051] Table 2 Homogenization conditions

[0052] Temperature (°C) Time (h) Example 1 1150 20 Example 2 1200 10 Example 3 1170 16 Example 4 1180 14

[0053] Step 2. Roll the homogenized alloy ingot at 150-200℃ above the γ′ precipitation temperature. The deformation amount in each pass is 10-20%, and the deformation amount in the last pass is greater than 20%. The final total deformation amount is 40-60%. After each hot rolling pass, the ingot is reheated in the furnace for 10-20 minutes.

[0054] Table 3 Hot-rolling parameters and heat preservation conditions

[0055]

[0056] The alloys in Examples 1-4 exhibited good hot working properties, and no defects such as cracks appeared during the hot working process.

[0057] Step 3. The hot-rolled alloy is solution treated at 140-180℃ above the γ′ phase precipitation temperature for 1-2 hours, and then solution treated at 80-100℃ above the γ′ phase precipitation temperature for 1.5-2.5 hours.

[0058] Step 4: The solution-treated alloy is aged at 280-320℃ for 10-14 hours below the γ′ phase precipitation temperature, and then aged at 100-140℃ for 2-6 hours below the γ′ phase precipitation temperature to obtain a low-expansion nickel-based high-temperature alloy.

[0059] Table 4 Solution treatment conditions

[0060]

[0061] Table 5 Time-sensitive processing conditions

[0062]

[0063] The low-expansion nickel-based superalloy obtained by this invention has an average grain size of 60-100 μm, and its typical grain structure characteristics are as follows: Figure 1 As shown. M is continuously distributed on the grain boundaries. 23 C6 type carbides, grain boundary M 23 C6 morphology as Figure 2 As shown. The intracrystalline γ′ phase size is 20-40 nm, and the morphology of the intracrystalline γ′ strengthening phase is as follows. Figure 3 As shown.

[0064] Table 6 Average Grain Size

[0065] Average grain size (μm) Example 1 75 Example 2 93 Example 3 72 Example 4 80

[0066] Comparative Example 1

[0067] This comparative example is basically the same as Example 1, except that it does not contain Co. The composition is shown in Table 7.

[0068] Comparative Example 2

[0069] This comparative example is basically the same as Example 1, except that the Ti / Al ratio in this comparative example is 1.2, and the composition is shown in Table 7.

[0070] Comparative Example 3

[0071] This comparative example is basically the same as Example 1, except that the Fe content in this comparative example is higher, and the composition is shown in Table 7.

[0072] Table 7 Chemical composition (mass %) of the comparative examples

[0073] Fe Cr Mo W Ti Al C B Zr Co Ni Nb Comparative Example 1 9 16 9 0.5 2.1 1.4 0.05 0.003 0.02 0 Bal. -- Comparative Example 2 9 16 9 0.5 2.1 1.75 0.05 0.003 0.02 2.0 Bal. Comparative Example 3 35 16 9 0.5 2.1 1.4 0.05 0.003 0.02 2.0 Bal.

[0074] Test case

[0075] Tensile property test: The tensile strength and yield strength of the alloy were tested at 650℃, and the test results are shown in Table 8.

[0076] Table 8. Properties of the alloy at 650℃

[0077]

[0078] As demonstrated in Examples 1-4, the alloy of the present invention exhibits both excellent high-temperature strength and excellent toughness. Furthermore, the average coefficient of linear expansion of the alloy of the present invention at temperatures ranging from 20 to 650°C is less than 15 × 10⁻⁶. -6 / ℃.

[0079] As can be seen from the comparison of Example 1 and Comparative Examples 1 and 3, both excessive Fe content and excessive Co content will reduce the strength of the alloy and increase the coefficient of thermal expansion at 20-650℃.

[0080] Long-term microstructure and performance stability: When the sum of Ti and Al does not change significantly, the Ti / Al ratio has no significant effect on the short-term strength of the alloy, but it will have a significant effect on the long-term microstructure stability of the alloy. Figure 4 The microstructure of the low-expansion nickel-based superalloy prepared in Example 1 after heat exposure at 650°C for 2300 h is shown. It can be seen that no harmful phases precipitate within the grains of the alloy after 2300 h of heat exposure, and M at the grain boundaries... 23 C6 type carbides and intracrystalline γ′ phase are stable. Figure 5 The microstructure of the low-expansion nickel-based superalloy prepared for Comparative Example 2 after heat exposure at 650℃ for 2300 h is shown. It can be seen that when the Ti / Al ratio is 1.2, needle-like harmful phases precipitate within the grains, which severely impairs the overall properties of the alloy.

[0081] Table 9 shows the tensile properties of Example 1 after heat exposure at 650℃. It can be seen that the alloy strength increases after long-term heat exposure, the plasticity decreases slightly but it still has excellent toughness.

[0082] Table 9 Tensile properties at 650℃ after heat exposure at 650℃

[0083]

[0084] Durability: Table 10 shows the durability performance. The alloy of this invention exhibits excellent durability performance.

[0085] Table 10 Durability

[0086]

[0087] In summary, the low-expansion nickel-based superalloy of the present invention has excellent high-temperature strength and toughness, hot working performance, oxidation resistance, good microstructure and performance stability, and can be used to manufacture high-parameter ultra-supercritical power plant turbine rotors, bolts, blades and valves, as well as structural components such as aero-engine casings and sealing rings.

[0088] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A low-expansion nickel-based superalloy, characterized in that, By mass percentage, it includes Fe: 6~10%, Cr: 12~20%, Mo: 6~12%, W: 0.2~0.8%, Ti: 1.8~2.4%, Al: 1.1~1.7%, C: 0.02~0.08%, B: 0.001~0.005%, Zr: 0.01~0.05%, Co: 1.7~2.3%, with the balance being Ni, where 1.4 < Ti / Al < 1.8; The preparation method of the low-expansion nickel-based superalloy includes the following steps: Step 1: Melt the raw materials under vacuum and cast them into alloy ingots. Homogenize the alloy ingots at 1150-1200℃ for 10-20 hours and then air cool them to room temperature. Step 2: Roll the homogenized alloy ingot at 150-200℃ above the γ´ phase precipitation temperature, with a deformation amount of 10-20% per pass, and a deformation amount of more than 20% in the last pass, for a final total deformation amount of 40-60%. Step 3: The rolled alloy is solution treated at 140-180℃ above the γ´ phase precipitation temperature for 1-2 hours, and then solution treated at 80-100℃ above the γ´ phase precipitation temperature for 1.5-2.5 hours. Step 4: The solution-treated alloy is aged at 280-320℃ for 10-14 hours below the γ´ phase precipitation temperature, and then aged at 100-140℃ for 2-6 hours below the γ´ phase precipitation temperature to obtain a low-expansion nickel-based high-temperature alloy.

2. The low-expansion nickel-based superalloy according to claim 1, characterized in that, The Fe content is 7-9% by mass; and / or The mass percentage content of Co is 1.8~2.2%.

3. The low-expansion nickel-based superalloy according to claim 1, characterized in that, The value is 1.5 ≤ Ti / Al ≤ 1.

7.

4. The nickel-based superalloy according to any one of claims 1-3, characterized in that, At least one of the following conditions must be met: (1) The mass percentage content of Cr is 14~18%; (2) The mass percentage content of Mo is 8-10%; (3) The mass percentage content of W is 0.4~0.6%; (4) The mass percentage content of Ti is 2.0~2.2%; (5) The Al content by mass percentage is 1.3~1.5%; (6) The mass percentage content of C is 0.04~0.06%; (7) The mass percentage content of B is 0.002~0.004%; (8) The Zr content is 0.02~0.04% by mass.

5. A method for preparing a low-expansion nickel-based superalloy according to any one of claims 1-4, characterized in that, Includes the following steps: Step 1: Melt the raw materials under vacuum and cast them into alloy ingots. Homogenize the alloy ingots at 1150-1200℃ for 10-20 hours and then air cool them to room temperature. Step 2: Roll the homogenized alloy ingot at 150-200℃ above the γ´ phase precipitation temperature, with a deformation amount of 10-20% per pass, and a deformation amount of more than 20% in the last pass, for a final total deformation amount of 40-60%. Step 3: The rolled alloy is solution treated at 140-180℃ above the γ´ phase precipitation temperature for 1-2 hours, and then solution treated at 80-100℃ above the γ´ phase precipitation temperature for 1.5-2.5 hours. Step 4: The solution-treated alloy is aged at 280-320℃ for 10-14 hours below the γ´ phase precipitation temperature, and then aged at 100-140℃ for 2-6 hours below the γ´ phase precipitation temperature to obtain a low-expansion nickel-based high-temperature alloy.

6. The method for preparing the low-expansion nickel-based superalloy according to claim 5, characterized in that, In step 2, after each rolling pass is completed, the material is returned to the furnace for heat preservation before proceeding to the next rolling pass.

7. The method for preparing a low-expansion nickel-based superalloy according to claim 6, characterized in that, In step 2, the temperature for each reheating is the same as the rolling temperature, and the reheating time is 10-20 minutes.

8. The method for preparing a low-expansion nickel-based superalloy according to any one of claims 5-7, characterized in that, The obtained low-expansion nickel-based superalloys have an average grain size of 60-100 μm, an intragranular γ´ phase size of 20-40 nm, and continuously distributed M... 23 C6 type carbides.

9. The application of the low-expansion nickel-based superalloy according to any one of claims 1-4 or the low-expansion nickel-based superalloy prepared by the method according to any one of claims 5-8 in high-parameter thermal power units or aero engines.

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