Preparation method of whole fine-grain strengthening isometric casting high-temperature alloy and application thereof

Abstract

The application discloses a preparation method of an integrally fine-grain-strengthened isometric casting high-temperature alloy and application thereof, and the preparation method comprises the following steps: refining a nickel-based high-temperature alloy ingot to obtain a refined alloy liquid; then cooling the refined alloy liquid to K1 and adding a grain refiner A to mix to obtain a mixed alloy liquid; and then heating the mixed alloy liquid to K2 to obtain a pouring alloy liquid, which is poured into a mold shell coated with a grain refiner B to obtain the integrally fine-grain-strengthened isometric casting high-temperature alloy. According to the method, proper pouring temperature and mold shell temperature provide suitable temperature gradient and cooling rate for the grain refiner and the surface refiner; the grain refiner mainly refines the core structure of the casting, the surface refiner mainly refines the surface structure of the casting, and the two can cooperate to effectively realize the integrally fine-grain-strengthened isometric casting from the surface to the core, improve the cross-section isometric crystal proportion of the nickel-based high-temperature alloy, obtain the uniform and fine isometric crystal structure of the integral structure part, and significantly improve the overall mechanical properties and high-temperature service stability of the casting.

Description

Technical Field

[0001] This invention belongs to the field of fine-grained casting technology of equiaxed high-temperature alloys, specifically relating to a method for preparing nickel-based high-temperature alloys that achieves overall fine-grained strengthening of castings and its application. Background Technology

[0002] Equiaxed casting high-temperature alloys, with their excellent medium- and high-temperature mechanical properties, good microstructural stability, and resistance to hot corrosion, are widely used in aero-engines and ground-based gas turbines, serving as indispensable key structural materials for hot-end components. With the urgent need for advanced aero-engines with high thrust-to-weight ratios, the design of aero-engine structural components is gradually shifting towards larger sizes, thinner walls, and greater complexity, placing higher demands on the microstructural uniformity and overall mechanical property consistency of high-temperature alloy castings. Existing conventional casting methods for high-temperature alloys typically employ high-temperature pouring temperatures to ensure good mold filling and avoid defects such as incomplete filling or under-pouring. However, high pouring temperatures and complex cooling conditions easily lead to the formation of fine surface grains, coarse through-grained grains in the core section, columnar grains, and uneven grain partitioning, making it impossible to achieve simultaneous grain refinement across the entire structural casting. Furthermore, the uneven grain distribution and low overall equiaxed grain ratio in equiaxed casting high-temperature alloys severely affect the alloy's high-temperature mechanical strength and plasticity, significantly reducing the overall service reliability and yield of castings, and severely restricting the large-scale application of large-size, complex-structure high-temperature alloy castings. Therefore, it is necessary to develop an equiaxed casting high-temperature alloy that achieves uniform and refined castings with excellent properties, and its preparation process.

[0003] The main fine-grain casting processes for equiaxed superalloys include thermal control, chemical, and kinetic methods. Chemical methods offer advantages such as maximizing grain refinement, simplicity, practicality, mature surface refining technology, and the absence of specialized equipment. This has significant practical implications for optimizing casting quality during production.

[0004] Therefore, a chemical method for overall fine-grain strengthening of equiaxed casting high-temperature alloys and its application are provided to achieve overall microstructure optimization of equiaxed casting high-temperature alloy castings. Summary of the Invention

[0005] To address the problem that existing technologies cannot achieve uniform grain refinement and consistent overall performance in equiaxed casting of high-temperature alloys, the first objective of this invention is to provide a method for preparing equiaxed casting of nickel-based high-temperature alloys that achieves overall grain refinement. Using this method, appropriate temperature gradients and cooling rates are provided for grain refiners and surface refiners through suitable casting and mold temperatures. The grain refiners and surface refiners provide heterogeneous nucleation sites for the alloy melt. The grain refiners primarily refine the core structure of the casting, while the surface refiners primarily refine the surface structure. This synergistic effect effectively achieves overall grain refinement from the surface to the core of the casting, increasing the proportion of equiaxed grains in the cross-section of the nickel-based high-temperature alloy, resulting in a uniform and fine equiaxed grain structure throughout the entire structural component, and significantly improving the overall comprehensive mechanical properties and high-temperature service stability of the casting.

[0006] The second objective of this invention is to provide an application of a nickel-based superalloy prepared by the above-described preparation method that achieves overall fine-grained strengthening.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This invention provides a method for preparing equiaxed casting nickel-based superalloys with overall fine grain strengthening. The method involves refining a nickel-based superalloy ingot to obtain a refined alloy liquid; then cooling the refined alloy liquid to K1 and adding a grain refiner A to obtain a mixed alloy liquid; then heating the mixed alloy liquid to K2 to obtain a casting alloy liquid, which is then poured into a mold shell with a grain refiner B coated on the inner surface.

[0009] The refining agent A is a composite refining agent composed of Cr-Fe-Nb refining agent and Co-Fe-Nb refining agent;

[0010] The inner surface of the mold shell is coated with a refining agent B, wherein the refining agent B is CoAl2O4;

[0011] The temperature of K1 is 20-30 ℃ lower than that of K2.

[0012] The preparation method provided by this invention involves refining a nickel-based superalloy ingot to obtain a refined alloy liquid, then lowering the temperature to a certain level and adding a grain refiner A, followed by further lowering the temperature to the pouring temperature and pouring the liquid into a mold coated with the grain refiner. By introducing a specific grain refiner through this invention, a large number of nucleation particles can be present in the refined alloy liquid of the nickel-based superalloy, which is beneficial for forming uniform and fine grains and promoting the uniform distribution of grains. The method of this invention can effectively achieve overall grain refinement of the casting from the surface to the core, increase the equiaxed grain ratio of the nickel-based superalloy cross section, obtain a uniform and fine equiaxed grain structure of the overall structural component, significantly improve the overall comprehensive mechanical properties and high-temperature service stability of the casting, and can increase the equiaxed grain ratio of the cross section to 99% or more.

[0013] Experiments have shown that adding a finer agent at a temperature 20℃-30℃ below the casting temperature, followed by increasing the melting power and raising the temperature to the casting temperature, can result in a better distribution of the finer agent and ultimately a better finer refining effect.

[0014] In a preferred embodiment, the nickel-based superalloy comprises equiaxed cast nickel-based superalloy K492M.

[0015] In a preferred embodiment, the refining temperature is 1500-1550 ℃, and the holding time is 1-2 min.

[0016] Experiments have shown that the refining temperature needs to be effectively controlled; if the refining temperature is too low, the grain refinement effect will be poor.

[0017] The preferred method involves cooling the refined alloy liquid to K1 before adding the refining agent A and mixing by oscillation for 8-12 seconds. Experiments have shown that oscillation can better ensure uniform mixing of the refined alloy liquid and the refining agent, resulting in highly homogenized temperature and composition of the alloy liquid, effectively reducing macroscopic segregation, and achieving a better overall refining effect compared to other methods such as stirring.

[0018] In a preferred embodiment, the refining agent A is coated with nickel foil. Coating the refining agent A with nickel foil before adding it to the alloy liquid results in a better refining effect.

[0019] In a preferred embodiment, the particle size of the refining agent A is 85-100 μm. Experiments have shown that controlling the particle size of the refining agent A within the above range yields the best refining effect. Refining agents with excessively large particle sizes cannot provide nucleation sites, while refining agents with excessively small particle sizes tend to spontaneously agglomerate. Therefore, both excessively large and excessively small particle sizes will reduce the refining effect.

[0020] In a preferred embodiment, the amount of refining agent A added is 0.1 to 0.3% of the mass of the nickel-based superalloy ingot.

[0021] In this invention, heat is released during heterogeneous nucleation. When there are few heterogeneous nuclei in the alloy melt, their mutual influence is small. However, if there are many heterogeneous nuclei in the alloy melt, the heat released during nucleation will cause the temperature of the alloy melt near the heterogeneous nuclei to rise above the non-uniform nucleation temperature. The supercooling of the heterogeneous nuclei becomes smaller, failing to reach the characteristic supercooling of heterogeneous nucleation. Therefore, some heterogeneous nuclei lose their effectiveness, inhibiting further nucleation. This invention controls the total mass of the refining agent to 0.1~0.3% of the mass of the nickel-based superalloy, ensuring the generation of a large number of nucleation particles and avoiding the loss of effectiveness of some heterogeneous nuclei, thus achieving the finest grain size of the final nickel-based superalloy.

[0022] In a preferred embodiment, the mass ratio of Cr-Fe-Nb refining agent to Co-Fe-Nb refining agent in refining agent A is 1~3:1.

[0023] Further preferred embodiments include the Cr-Fe-Nb refining agent, in which the atomic ratio of Cr, Fe, and Nb is 1:1:1, and the Co-Fe-Nb refining agent, in which the atomic ratio of Co, Fe, and Nb is 3:1:2. Experiments have shown that the refining agents with the above atomic ratios, when combined, achieve the optimal refining effect.

[0024] In a preferred embodiment, the casting temperature K2 of the nickel-based superalloy is 1400-1420 ℃.

[0025] In a preferred embodiment, the preheating temperature of the mold shell is 900~950 ℃, and the heat preservation time is 20-30 min.

[0026] Experiments have shown that controlling the casting temperature and mold temperature within the above range yields the best refining effect. The casting temperature and mold temperature provide a sufficiently large temperature gradient and cooling rate for the refining agent, and on the other hand, provide a stable melt environment for the refining agent, preventing the refining agent from accumulating inside the melt and failing to provide nucleation sites in certain areas.

[0027] If the casting temperature and the mold temperature are not within the range of this invention, the corresponding temperature gradient and cooling rate cannot be provided, and the refining effect of the refining agent will be difficult to achieve.

[0028] This invention provides an equiaxed cast nickel-based superalloy with overall grain refinement prepared by the above-described preparation method.

[0029] In a preferred embodiment, the average grain size of the equiaxed cast nickel-based superalloy achieving overall grain refinement is 138.66 ± 3.65 µm, and the equiaxed grain ratio in the cross-section is 97.19%.

[0030] On the other hand, the present invention also provides an application of a fine-grained reinforced nickel-based superalloy prepared by the above preparation method, wherein the fine-grained reinforced nickel-based superalloy is applied to aero-engine castings.

[0031] Beneficial effects of this invention:

[0032] 1. By introducing specific refining agents, a large number of nucleation particles can be present in the refined alloy liquid of equiaxed cast nickel-based superalloys, which is conducive to the formation of uniform and fine grains and promotes the uniform distribution of grains.

[0033] 2. By controlling the particle size and amount of the refining agent, the required grain size of the nickel-based superalloy can be controlled, thus achieving a uniform and fine equiaxed grain structure in the nickel-based superalloy.

[0034] 3. The results of the examples show that the average grain size of the nickel-based superalloy prepared by the method of the present invention can reach 138.66±3.65 µm, the equiaxed grain ratio of the cross section can be increased to 97.19%, the yield strength of the fine-grained strengthened nickel-based superalloy at 760℃ is 978.76 MPa, the elongation is 12.50%, and the tensile strength is 1147.95 MPa. Attached Figure Description

[0035] Figure 1 The image shows the overall grain structure of the feature shaft area of ​​the casting obtained in Comparative Example 1 without the addition of a grain refiner.

[0036] Figure 2 This is a grain structure diagram of the overall fine-grained strengthening of the characteristic shaft region of the casting obtained in Example 1.

[0037] Figure 3 The image shows the overall grain structure of the feature plate area of ​​the casting obtained in Comparative Example 2 without the addition of a grain refiner.

[0038] Figure 4 This is a grain structure diagram of the overall fine-grained strengthening of the feature disk area of ​​the casting obtained in Example 2.

[0039] Figure 5 The image shows the overall grain structure morphology of the core region of the casting obtained in Comparative Example 3 without the addition of a grain refiner.

[0040] Figure 6 This is a grain structure diagram of the overall fine-grained strengthening of the core region of the casting obtained in Comparative Example 3.

[0041] Figure 7 Tensile properties of K492M alloy without refiner and integrally refined alloy under tensile conditions at 760℃. Detailed Implementation

[0042] This invention provides an equiaxed cast nickel-based superalloy with overall fine-grained strengthening and its preparation method, comprising the following steps:

[0043] Refining nickel-based superalloy ingots yields refined alloy liquid;

[0044] After cooling the refined alloy liquid to K1, add the refining agent A, and ensure that the refined alloy liquid and the refining agent are mixed evenly by shaking.

[0045] The uniformly mixed molten alloy is heated to K2 to obtain a casting molten alloy, which is then poured into a mold shell whose inner surface is coated with a finer agent B.

[0046] As one embodiment of the present invention, the nickel-based superalloy includes equiaxed cast nickel-based superalloy K492M and its content is shown in Table 1.

[0047] Table 1. Elemental composition and content (wt.%) of nickel-based superalloys

[0048]

[0049] As one embodiment of the present invention, the nickel-based high-temperature alloy ingot is divided into appropriately sized blocks using an electric discharge cutting machine, and its surface is polished to a bright finish using a grinding wheel. Then, it is ultrasonically cleaned with alcohol for 10-15 minutes, dried, and 1.5 kg is weighed for later use.

[0050] In one embodiment of the present invention, the refining temperature of the nickel-based high-temperature alloy is 1520-1550 ℃, and the holding time is 1-2 min.

[0051] In one embodiment of the present invention, the temperature of K1 is 20-30 ℃ lower than that of K2, and the casting temperature of the nickel-based high-temperature alloy K2 is 1400-1420 ℃;

[0052] In one embodiment of the present invention, the oscillation time of the alloy liquid is 8-12 s;

[0053] In one embodiment of the present invention, the refining agent A comprises a composite refining agent composed of Cr-Fe-Nb refining agent and Co-Fe-Nb refining agent in a mass ratio of 1:1; in the Cr-Fe-Nb refining agent, the atomic ratio of Cr, Fe and Nb is 1:1:1, and in the Co-Fe-Nb refining agent, the atomic ratio of Co, Fe and Nb is 3:1:2;

[0054] As one embodiment of the present invention, the average particle size of the composite refining agent is controlled to be 87.5 μm. It is weighed at 0.1% of the alloy weight, and after weighing, it is wrapped with nickel foil for later use.

[0055] In one embodiment of the present invention, the refining agent B coated on the inner surface of the mold shell is the surface refining agent CoAl2O4;

[0056] In one embodiment of the present invention, the preheating temperature of the mold shell is 900~950 ℃, and the heat preservation time is 20-30 min;

[0057] In the embodiments and comparative examples of this invention, a vacuum induction melting furnace with a feeding system is used for alloy melting, refining, adding refining agents, and casting. The prepared alloy material is placed in a crucible, and a composite refining agent wrapped in nickel foil is added to the feeding system; the furnace door is closed, and the vacuum inside the furnace is sequentially evacuated to 1×10⁻⁶ using a mechanical pump, a Roots pump, and a diffusion pump. -3Pa, turn on the heating element to heat the mold shell to 910 ℃, and turn on the melting power after the heating element reaches the temperature; after the alloy melts, control its temperature at 1550 ℃ for 2 minutes to refine, and then reduce it to 1390 ℃. Add the composite refining agent wrapped in nickel foil through the feeding system and shake for 8 seconds to mix evenly. Then raise the temperature to 1410 ℃ to obtain the casting alloy liquid. Pour the casting alloy liquid into the preheated mold shell. After the casting is completed, turn off the heating element. After the furnace temperature drops to room temperature, remove the mold shell to obtain the refined casting.

[0058] In this invention, the growth conditions for isometric crystals in nickel-based superalloys can be expressed by the following formula:

[0059] (1)

[0060] In the formula, G is the temperature gradient at the solid-liquid interface front (K / m), η is the transformation coefficient from columnar to equiaxed crystals in the alloy, which is related to the alloy composition, and n is the density of heterogeneous nucleated particles per unit volume (m-3). The critical undercooling (K) for heterogeneous nucleation. The supercooling (K) at the growth front of columnar crystals. R is the solidification growth rate (m / s), C0 is the alloy composition (wt.%), m is the slope of the alloy liquidus line (K / wt.%), Γ is the Gibbs–Thomson coefficient (m·K), which is the ratio of the solid-liquid interface energy to the alloy melting entropy, k0 is the partition coefficient, and D is the diffusion coefficient (m). 2 / s). In this invention, the addition of a grain refiner does not change the composition of the alloy, but only alters the particle density n of heterogeneous nucleation per unit volume and the critical undercooling of heterogeneous nucleation. It increased n and decreased This causes the right side of equation (1) to increase under the same temperature gradient, satisfying the inequality. The growth of columnar crystals is suppressed, and the alloy grows in an equiaxed crystal manner.

[0061] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0062] Comparative Example 1

[0063] The K492M nickel-based high-temperature alloy ingot was cut into appropriately sized blocks using an EDM machine. The surface of the blocks was polished to a bright finish using a grinding wheel. Then, the blocks were ultrasonically cleaned with alcohol for 10 minutes, dried, and 1.5 kg was weighed for later use.

[0064] The mold shell surface is coated with a surface refiner, CoAl2O4;

[0065] In this comparative example, a vacuum induction melting furnace with a feeding system was used for alloy melting, refining, adding refining agents, and casting. The prepared alloy material was placed in the crucible, the furnace door was closed, and the vacuum inside the furnace was sequentially evacuated to 1×10⁻⁶ using a mechanical pump, a Roots pump, and a diffusion pump. -3 Pa, turn on the heating element to heat the mold shell to 910 ℃, and turn on the melting power supply after the heating element reaches the temperature; after the alloy melts, control its temperature at 1550 ℃ for 2 minutes to refine, then reduce it to 1390 ℃ and oscillate for 8 seconds, and then raise the temperature to 1410 ℃ to obtain the casting alloy liquid, pour the casting alloy liquid into the preheated mold shell, turn off the heating element after pouring, and take out the mold shell after the furnace temperature drops to room temperature to obtain the refined casting;

[0066] The casting prepared in this comparative example was sampled, ground, mechanically polished, and etched at its characteristic shaft area. Electron backscatter diffraction (EBSD) analysis was then used to characterize the overall grain size of the characteristic casting, yielding the following overall grain structure: Figure 1 As shown. The casting obtained in Comparative Example 1 has elongated columnar crystals at its characteristic axis region, which extend into the interior of the casting. The interior of the casting axis region is composed of coarse equiaxed crystals. The overall grain size at the characteristic axis region of the casting is 218.37±5.51 µm, and the proportion of equiaxed crystals in the cross section is only 58.25%.

[0067] Comparative Example 2

[0068] The preparation method is exactly the same as that of Comparative Example 1, except that the overall grain size of the feature disk area of ​​the casting is characterized to obtain the overall grain structure of the casting as shown in Figure 1. Figure 2 As shown in the figure, a coarse equiaxed grain structure appeared on the outer surface of the feature disk area of ​​the casting prepared in Comparative Example 2. The overall grain size of the feature disk area of ​​the casting was 200.61±7.35 µm, and the equiaxed grain ratio in the cross section was 78.71%.

[0069] Comparative Example 3

[0070] The preparation method is exactly the same as that of Comparative Example 1, except that the overall grain size of the feature core area of ​​the casting is characterized to obtain the overall grain structure of the casting as shown in Figure 1. Figure 3 As shown. The core of the casting prepared in Comparative Example 3 has a relatively large grain size, and columnar crystals appear on its surface, while the interior has a coarse equiaxed crystal structure. The overall grain size of the core of the casting is 258.86±5.32 µm, and the proportion of equiaxed crystals in the cross section is 80.65%.

[0071] Example 1

[0072] The preparation method is basically the same as that of Comparative Example 1, except that the composite refining agent obtained by mixing the refining agents Cr-Fe-Nb and Co-Fe-Nb in a mass ratio of 1:1 is controlled to have an average particle size of 87.5 μm. It is weighed at 0.1 wt% of the alloy weight, and after weighing, it is wrapped in nickel foil for later use.

[0073] The mold shell surface is coated with a surface refiner, CoAl2O4;

[0074] In Example 1, a vacuum induction melting furnace with a feeding system was used for alloy melting, refining, adding refining agents, and casting. The prepared alloy material was placed in a crucible, and a composite refining agent wrapped in nickel foil was added to the feeding system. The furnace door was closed, and the vacuum inside the furnace was sequentially evacuated to 1×10⁻⁶ using a mechanical pump, a Roots pump, and a diffusion pump. -3 Pa, turn on the heating element to heat the mold shell to 910 ℃, and turn on the melting power after the heating element reaches the temperature; after the alloy melts, control its temperature at 1550 ℃ for 2 minutes to refine, and then reduce it to 1390 ℃. Add the composite refining agent wrapped in nickel foil through the feeding system and shake for 8 seconds to mix evenly. Then raise the temperature to 1410 ℃ to obtain the casting alloy liquid. Pour the casting alloy liquid into the preheated mold shell. After the casting is completed, turn off the heating element. After the furnace temperature drops to room temperature, remove the mold shell to obtain the refined casting.

[0075] The overall grain size of the characteristic shaft region of the casting prepared in Example 1 was characterized, and the overall grain structure of the casting was obtained as follows: Figure 4 As shown. The grain size of the feature shaft region of the casting prepared in Example 1 is significantly refined, with the overall grain size of the feature shaft region being 138.66±3.65 µm, and the proportion of equiaxed grains in the cross-section increasing to 97.19%.

[0076] Example 2

[0077] The preparation method is exactly the same as in Example 1, except that the overall grain size of the feature disk area of ​​the casting is characterized to obtain the overall grain structure of the casting as shown in Example 1. Figure 5 As shown. The grain size of the feature disk region of the casting prepared in Example 2 is significantly refined, the proportion of columnar crystals is reduced, the overall grain size of the feature disk region of the casting is 112.90±2.45 µm, and the proportion of equiaxed crystals in the cross section is 96.35%.

[0078] Example 3

[0079] The preparation method is exactly the same as in Example 1, except that the overall grain size of the core area of ​​the casting is characterized to obtain the overall grain structure of the casting as shown in Example 1. Figure 6As shown. The grain size of the feature core of the casting prepared in Example 3 is significantly refined, the proportion of columnar crystals on the surface is reduced, the overall grain size of the feature core is 138.72±3.86 µm, and the proportion of equiaxed crystals in the cross section is 95.28%.

[0080] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing equiaxed cast nickel-based superalloys with overall fine-grained strengthening, characterized in that: The nickel-based superalloy ingot is refined to obtain a refined alloy liquid; then the refined alloy liquid is cooled to K1 and then a refining agent A is added and mixed to obtain a mixed alloy liquid; then the mixed alloy liquid is heated to K2 to obtain a casting alloy liquid, which is poured into a mold shell with a refining agent B on the inner surface. The refining agent A is a composite refining agent composed of Cr-Fe-Nb refining agent and Co-Fe-Nb refining agent; The inner surface of the mold shell is coated with a refining agent B, wherein the refining agent B is CoAl2O4; The temperature of K1 is 20-30 ℃ lower than that of K2.

2. The preparation method for achieving overall fine-grained strengthening of equiaxed cast nickel-based superalloys according to claim 1, characterized in that: The nickel-based superalloy includes the equiaxed crystal cast nickel-based superalloy K492M.

3. The preparation method for achieving overall fine-grained strengthening of equiaxed cast nickel-based superalloys according to claim 1, characterized in that: The refining temperature is 1500-1550 ℃, and the holding time is 1-2 min.

4. The preparation method for achieving overall fine-grained strengthening of equiaxed cast nickel-based superalloys according to claim 1, characterized in that: The method of cooling the refined alloy liquid to K1 and then adding the refining agent A is to mix by oscillation for 8-12 seconds. The refining agent A is wrapped in nickel foil.

5. A method for preparing equiaxed cast nickel-based superalloys with overall fine-grained strengthening according to claim 1 or 4, characterized in that: The particle size of the refining agent A is 85-100 μm; The amount of refining agent A added is 0.1~0.3% of the mass of the nickel-based superalloy ingot; In the refining agent A, the mass ratio of Cr-Fe-Nb refining agent to Co-Fe-Nb refining agent is 1~3:

1.

6. A method for preparing equiaxed cast nickel-based superalloys with overall fine-grained strengthening according to claim 1 or 4, characterized in that: In the Cr-Fe-Nb refining agent, the atomic ratio of Cr, Fe and Nb is 1:1:1, and in the Co-Fe-Nb refining agent, the atomic ratio of Co, Fe and Nb is 3:1:

2.

7. The preparation method for achieving overall fine-grained strengthening of equiaxed cast nickel-based superalloys according to claim 1, characterized in that: The casting temperature K2 of the nickel-based superalloy is 1400-1420 ℃.

8. The preparation method for achieving overall fine-grained strengthening of equiaxed cast nickel-based superalloys according to claim 1, characterized in that: The preheating temperature of the mold shell is 900~950 ℃, and the holding time is 20-30 min.

9. An equiaxed cast nickel-based superalloy with overall grain refinement prepared by the preparation method according to any one of claims 1-8.

10. The application of an equiaxed cast nickel-based superalloy with overall grain refinement prepared by the preparation method according to any one of claims 1-8, characterized in that: The fine-grained reinforced nickel-based superalloy is applied to aero-engine castings.

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