Grain-refined nickel-based superalloy as well as preparation method and application thereof

Abstract

The invention relates to the technical field of high-temperature alloy fine grain casting, and particularly provides a grain-refined nickel-based high-temperature alloy and a preparation method and application thereof. The preparation method of the grain refined nickel-based superalloy comprises the following steps that the nickel-based superalloy is refined, the temperature of an obtained melt is reduced to the pouring temperature, and a poured melt is obtained; mixing the pouring melt with a refiner, and pouring the mixture into a heat preservation mold shell; and the heat preservation mold shell is pulled from the hot area to the cold area, and the grain-refined nickel-based superalloy is obtained. By introducing the refiner, the grain size of the nickel-based superalloy can be remarkably refined, the proportion of equiaxed crystals on the section is increased, and the equiaxed crystals are uniformly dispersed and fine.

Description

Technical Field

[0001] The invention relates to the technical field of fine-grain casting of high-temperature alloys, and specifically provides a grain-refined nickel-based high-temperature alloy and a preparation method and application thereof. Background Art

[0002] Nickel-based high-temperature alloys are widely used in aircraft engines and ground gas turbines due to their excellent medium- and high-temperature mechanical properties and good structural stability. They are indispensable key structural materials for hot end components. In recent years, the structural design of advanced aircraft engines has tended to be more precise, large-scale, and hollow and thin-walled. Therefore, this type of casting should ensure uniform and fine equiaxed grains under the premise of filling the mold.

[0003] Existing high-temperature alloy casting technologies include conventional casting, thermally controlled solidification process, new thermally controlled solidification process, counter-gravity casting and centrifugal casting. Conventional casting and thermally controlled solidification process may produce defects such as shrinkage and shrinkage holes when preparing large and complex thin-walled castings due to shrinkage compensation limitations, which will affect the service life of the castings. The new thermally controlled solidification process, counter-gravity casting and centrifugal casting can achieve good filling of the casting by applying external force, but counter-gravity casting and centrifugal casting are easily limited by equipment and mold strength and are difficult to control. The new thermally controlled solidification process is a process derived from the conventional thermally controlled solidification process. Due to the high mold shell insulation temperature and sequential solidification, the melt state of the alloy can be controlled to achieve good filling of large and complex castings, but the resulting casting has a coarse and uneven grain structure. Summary of the invention

[0004] The purpose of the present invention is to provide a grain-refined nickel-based high-temperature alloy and a preparation method and application thereof. The method of the present invention can significantly refine the grain size of the nickel-based high-temperature alloy, increase the equiaxed crystal ratio of the nickel-based high-temperature alloy cross section, and make the equiaxed crystals dispersed evenly and finely.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for preparing a grain-refined nickel-based high-temperature alloy comprises the following steps:

[0007] Refining the nickel-based high-temperature alloy, lowering the temperature of the obtained melt to a pouring temperature, and obtaining a pouring melt;

[0008] The casting melt is mixed with a refiner and cast into a heat-insulating mold shell;

[0009] The heat-insulating mold shell is pulled from the hot zone to the cold zone to obtain the grain-refined nickel-based high-temperature alloy.

[0010] Preferably, the nickel-based high-temperature alloy includes nickel-based high-temperature alloy IN939 or nickel-based high-temperature alloy IN718.

[0011] Preferably, the refiner includes a Cr-Fe-Nb refiner and a Co-Fe-Nb refiner; the molar ratio of Cr, Fe and Nb in the Cr-Fe-Nb refiner is 1:1:1; the molar ratio of Co, Fe and Nb in the Co-Fe-Nb refiner is 3:1:2; the mass ratio of the Cr-Fe-Nb refiner to the Co-Fe-Nb refiner is 1:1.

[0012] Preferably, the mesh sizes of the Cr-Fe-Nb refiner and the Co-Fe-Nb refiner are independently 100-250 meshes; the total mass of the Cr-Fe-Nb refiner and the Co-Fe-Nb refiner is 0.1-0.3% of the mass of the nickel-based high-temperature alloy.

[0013] Preferably, the pulling rate is 400-550 μm / s.

[0014] Preferably, the refining temperature is 150-200° C. higher than the liquidus of the nickel-based high-temperature alloy, and the refining time is 2-3 min.

[0015] Preferably, the pouring temperature is 40-80° C. higher than the liquidus of the nickel-based high-temperature alloy.

[0016] Preferably, the temperature of the insulation shell is the temperature between the solid-liquid phase zone of the nickel-based high-temperature alloy.

[0017] The present invention provides a grain-refined nickel-based high-temperature alloy prepared by the preparation method described in the above scheme, wherein the average grain size of the grain-refined nickel-based high-temperature alloy is 129-2918 μm, the proportion of equiaxed crystals in the cross section is 84-98%, and the proportion of shrinkage porosity is 0.003-0.054%.

[0018] The present invention provides application of the grain-refined nickel-based high-temperature alloy described in the above scheme in aero-engine castings.

[0019] The present invention provides a method for preparing a grain-refined nickel-based high-temperature alloy, comprising the following steps: refining the nickel-based high-temperature alloy, lowering the temperature of the resulting melt to a pouring temperature, and obtaining a pouring melt; mixing the pouring melt with a refiner, and pouring it into a heat-insulating mold shell; and pulling the heat-insulating mold shell from a hot zone to a cold zone to obtain the grain-refined nickel-based high-temperature alloy. The present invention introduces a refiner so that a large number of nucleation particles exist in the refined melt of the nickel-based high-temperature alloy, which is conducive to forming uniform and fine grains and promoting uniform distribution of grains.

[0020] Furthermore, the present invention controls the grain size required for the nickel-based high-temperature alloy by controlling the mesh size and addition amount of the refiner, thereby achieving uniform and fine equiaxed grains in the nickel-based high-temperature alloy while ensuring a low shrinkage rate. The results of the embodiment show that the average grain size of the nickel-based high-temperature alloy prepared by the method of the present invention can reach 129 μm, and the proportion of equiaxed grains in the cross section can be increased to 98%. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The specific grain macrostructure photo and shrinkage and shrinkage cavity statistical diagram of the grain-refined nickel-based high-temperature alloy after adding 150-200 mesh refiner in Example 1;

[0022] Figure 2 The specific grain macrostructure photo and shrinkage and shrinkage cavity statistical diagram of the grain-refined nickel-based high-temperature alloy after adding 100-150 mesh refiner in Example 2;

[0023] Figure 3 The specific grain macrostructure photo and shrinkage and shrinkage cavity statistical diagram of the grain refined nickel-based high-temperature alloy after adding 200-250 mesh refiner in Example 3;

[0024] Figure 4 The specific grain macrostructure photos and shrinkage and porosity statistics of nickel-based high-temperature alloys without adding refiners;

[0025] Figure 5 The longitudinal cross-section diagram of the grain-refined nickel-based superalloy without adding a refiner and after adding 0.1wt% of a refiner with different mesh sizes;

[0026] Figure 6 The longitudinal section of the grain-refined nickel-based superalloy after adding different contents and mesh sizes of refiners;

[0027] Figure 7 Schematic diagram of the overall experimental process. DETAILED DESCRIPTION

[0028] The present invention provides a method for preparing a grain-refined nickel-based high-temperature alloy, comprising the following steps:

[0029] Refining the nickel-based high-temperature alloy, lowering the temperature of the obtained melt to a pouring temperature, and obtaining a pouring melt;

[0030] The casting melt is mixed with a refiner and cast into a heat-insulating mold shell;

[0031] The heat-insulating mold shell is pulled from the hot zone to the cold zone to obtain the grain-refined nickel-based high-temperature alloy.

[0032] In the present invention, unless otherwise specified, all preparation raw materials / components are commercially available products well known to those skilled in the art.

[0033] The invention refines the nickel-based high-temperature alloy, reduces the temperature of the obtained melt to the pouring temperature, and obtains the pouring melt.

[0034] As an embodiment of the present invention, the nickel-based high-temperature alloy may include nickel-based high-temperature alloy IN939 or nickel-based high-temperature alloy IN718. The components and contents of the nickel-based high-temperature alloy IN939 and nickel-based high-temperature alloy IN718 are shown in Table 1 and Table 2, respectively.

[0035] Table 1 Element composition and content (wt%) in nickel-based superalloy IN939

[0036] element Cr Co Al Ti W Ta Nb C Zr B Ni content 22.5 19 1.9 3.7 2 1 1.4 0.15 0.1 0.009 Bal.

[0037] Table 2 Element composition and content (wt%) in nickel-based superalloy IN718

[0038] element C Al Cr Mo Nb Fe Mn Si Cu Ti S B Ni content 0.0191 0.23 19.14 3.13 5.41 18.63 0.044 0.18 0.028 0.76 0.0011 0.003 Bal.

[0039] As an embodiment of the present invention, the nickel-based high-temperature alloy is preferably pretreated before use; the pretreatment preferably includes: dividing the nickel-based high-temperature alloy into blocks using an electric spark cutter, grinding the blocks using a grinder, ultrasonically cleaning the ground blocks with a solvent, and then drying for use. As an embodiment of the present invention, the solvent used for the ultrasonic cleaning includes ethanol, and the ultrasonic cleaning time can be 5 to 10 minutes; the present invention has no special limitation on the drying.

[0040] As an embodiment of the present invention, the refining temperature can be 150-200°C higher than the liquidus of the nickel-based high-temperature alloy, and the refining time can be 2-3 minutes, specifically 2 minutes. The liquidus of the nickel-based high-temperature alloy IN939 is between 1332±1°C. The present invention controls the refining temperature of the nickel-based high-temperature alloy to ensure that impurities and gases in the nickel-based high-temperature alloy can be fully removed. In a specific embodiment of the present invention, the refining temperature can be 1520±10°C.

[0041] As an embodiment of the present invention, the pouring temperature is 40 to 80°C higher than the liquidus of the nickel-based high-temperature alloy. The present invention controls the pouring temperature to ensure that the pouring melt remains in a liquid state during the pouring process, while avoiding overheating that causes grain coarsening. In a specific embodiment of the present invention, the pouring temperature can be 1380±10°C.

[0042] After obtaining the casting melt, the present invention mixes the casting melt with a refiner and casts the mixture into a heat-insulating mold shell.

[0043] As an embodiment of the present invention, the refiner preferably includes a Cr-Fe-Nb refiner and a Co-Fe-Nb refiner; the molar ratio of Cr, Fe and Nb in the Cr-Fe-Nb refiner may be 1:1:1; the molar ratio of Co, Fe and Nb in the Co-Fe-Nb refiner may be 3:1:2; the mass ratio of the Cr-Fe-Nb refiner to the Co-Fe-Nb refiner may be 1:1.

[0044] As an embodiment of the present invention, the mesh sizes of the Cr-Fe-Nb refiner and the Co-Fe-Nb refiner are independently 100-250 meshes, specifically 100-150 meshes, 150-200 meshes or 200-250 meshes; the total mass of the Cr-Fe-Nb refiner and the Co-Fe-Nb refiner is 0.1-0.3% of the mass of the nickel-based high-temperature alloy, specifically 0.1%, 0.15%, 0.2%, 0.25% or 0.3%.

[0045] In the present invention, a refiner with too large a particle size cannot provide nucleation points for the refiner, and a refiner with too small a particle size tends to spontaneously agglomerate due to the influence of van der Waals force. The present invention controls the mesh size of the refiner to 100 to 250 meshes, which can ensure that the obtained grains are small and uniform.

[0046] In the present invention, heat is released during heterogeneous nucleation. When there are few heterogeneous cores in the melt, their mutual influence is small; if there are many heterogeneous cores in the melt, the heat released during nucleation will cause the temperature of the melt near the heterogeneous core to rise above the non-uniform nucleation temperature, and the supercooling of the heterogeneous core becomes smaller, and the characteristic supercooling of the heterogeneous core nucleation cannot be reached, so some heterogeneous cores lose their effectiveness, inhibiting further nucleation. The present invention controls the total mass of the refiner to be 0.1-0.3% of the mass of the nickel-based high-temperature alloy, ensuring that a large number of nucleation particles are generated and the grain size of the nickel-based high-temperature alloy is refined.

[0047] As an implementation mode of the present invention, the refiner can be added into the casting melt and shaken for 3 to 8 seconds to ensure that the casting melt and the refiner are evenly mixed.

[0048] As an embodiment of the present invention, the temperature of the insulation mold shell is preferably a temperature between the solid and liquid phase zones of the nickel-based high-temperature alloy. The present invention controls the temperature of the mold shell insulation to ensure that the nickel-based high-temperature alloy can be smoothly compensated for shrinkage during the subsequent pulling process and delay the dendrite overlap time. In a specific embodiment of the present invention, the temperature of the insulation mold shell can be 1290-1320°C.

[0049] After being poured into the heat-insulating mold, the invention pulls the heat-insulating mold from the hot zone to the cold zone to obtain the grain-refined nickel-based high-temperature alloy.

[0050] As an embodiment of the present invention, the pulling rate may be 400-550 μm / s, specifically 400 μm / s.

[0051] In the embodiment of the present invention, the nickel-based high-temperature alloy is melted, refined, poured and drawn in a directional solidification furnace; the directional solidification furnace includes a feeding system and a drawing system, which are respectively used to add a refiner and draw. In the embodiment of the present invention, the nickel-based high-temperature alloy is placed in a crucible of a directional solidification furnace, the refiner is wrapped in Ni foil, the wrapped refiner is placed in the feeding system, the furnace door is closed, and a mechanical pump, a Roots pump and a diffusion pump are used in turn to evacuate the furnace (the vacuum degree can be 1×10 -3 ~2×10 -3 Pa, specifically 1×10 -3 Pa), turn on the heating body (mold shell insulation) system to heat the mold shell to the mold shell insulation temperature, turn on the smelting power supply after the heating body reaches the temperature, and after the nickel-based high-temperature alloy is melted, control the temperature at the refining temperature for refining, and then reduce it to the pouring temperature to obtain a pouring melt; add a pre-prepared refiner to the pouring melt and shake and mix it evenly, and pour it into the mold shell; after the pouring is completed, turn on the pulling system of the directional solidification furnace to pull, and stop pulling after the mold shell is completely pulled out of the heating zone, turn off the heating body, and take out the mold shell after the temperature in the furnace drops to room temperature to obtain a grain-refined nickel-based high-temperature alloy.

[0052] The present invention realizes directional solidification in the process of pulling the mold shell from the hot zone to the cold zone, and finally obtains the grain-refined nickel-based high-temperature alloy.

[0053] As an embodiment of the present invention, during the directional solidification process, the grains of the nickel-based high-temperature alloy will transform from columnar crystals to equiaxed crystals as the pulling rate changes. The condition for the appearance of equiaxed crystals at the front of the columnar crystals can be expressed by the following formula:

[0054]

[0055] Where: G is the temperature gradient at the tip of the dendrite at the growth front of the columnar crystal (K / m); η is the conversion coefficient of columnar crystals and equiaxed crystals, which is related to the alloy composition; n represents the number of substrate particles available for non-uniform nucleation per unit volume (m -3 );ΔTN is the undercooling degree of heterogeneous nucleation (K); ΔTc is the undercooling degree of the liquid phase at the front of the columnar crystal (K); ΔTc∝(RC 0 ) 1 / 2 , where R is the growth rate (m / s), C 0 is the initial content of solute carbon (wt%); Γ is the Gibbs-Thomson coefficient (m·K); m is the liquidus slope (K / wt%); k 0is the solute distribution coefficient; D is the solute diffusion coefficient (m 2 / s).

[0056] The present invention can reduce G and increase n, R and -mC by controlling the pulling rate to 400 μm / s. 0 (1-k 0 ), which is conducive to the formation of equiaxed crystals.

[0057] As an embodiment of the present invention, after the drawing is completed, the size of the obtained grain-refined nickel-based high-temperature alloy can be Φ30mm×60mm.

[0058] As an embodiment of the present invention, after the pulling, it is preferred that the grain-refined nickel-based high-temperature alloy is post-processed; the post-processing may include: sampling, grinding, mechanical polishing and vibration polishing of the grain-refined nickel-based high-temperature alloy in sequence; the present invention has no special limitation on the specific methods of the sampling, grinding, mechanical polishing and vibration polishing, all of which are conventional methods in the field.

[0059] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0060] Example 1

[0061] The IN939 nickel-based high-temperature alloy ingot was cut into blocks by an electric spark cutting machine, the surface of which was polished to brightness by a grinder, ultrasonically cleaned with ethanol for 5 minutes, and 1200 g of the IN939 nickel-based high-temperature alloy was weighed and set aside after drying.

[0062] CrFeNb refiner with mesh size of 150-200 and Co 3 FeNb 2 The refiners are mixed in a mass ratio of 1:1 to obtain a composite refiner. The mass of the composite refiner is weighed to be 0.1wt% of the IN939 nickel-based high-temperature alloy. After weighing, the composite refiner is wrapped with nickel foil for standby use.

[0063] Put the IN939 nickel-based superalloy into the crucible of a directional solidification furnace with a pulling and feeding system, and put the wrapped composite refiner into the feeding system in advance. Close the furnace door, and use a mechanical pump, a Roots pump, and a diffusion pump to evacuate the furnace to a vacuum of 1×10 -3Pa, turn on the heating body (mold shell insulation) system, heat the mold shell to 1300℃, and turn on the smelting power supply after the heating body reaches the temperature. After the IN939 nickel-based high-temperature alloy is melted, the temperature is controlled at 1520℃ for refining for 2min, and then lowered to the pouring temperature of 1380℃, and the composite refiner prepared in advance is added and shaken evenly, and poured into the mold shell; after the pouring is completed, the pulling system of the directional solidification furnace is turned on, and the pulling is performed at 400μm / s. After the mold shell is completely pulled out of the heating zone, the pulling is stopped, the heating body is turned off, and the mold shell is taken out after the temperature in the furnace drops to room temperature to obtain a grain-refined nickel-based high-temperature alloy.

[0064] The grain-refined nickel-based superalloy prepared in this embodiment has a size of Φ30 mm×60 mm. The grain-refined nickel-based superalloy is sampled, ground, mechanically polished and vibratedly polished in sequence, and the grain size of the alloy is characterized by electron backscattered diffraction analysis technology (EBSD) using a field emission scanning electron microscope (Zeiss Gemini Sigma 300) with a Symmetry S3 probe and Aztec 6.0 software. The specific grain macroscopic structure photos are shown in FIG. Figure 1 As shown in a in the figure; using Leica stereoscope to observe and take pictures, the shrinkage statistics diagram is as follows Figure 1 As shown in b in the figure, the average grain size of the grain-refined nickel-based high-temperature alloy obtained in Example 1 is 129 μm, the proportion of equiaxed grains in the cross section is 98%, and the proportion of shrinkage porosity is 0.003%.

[0065] Embodiment 2:

[0066] The preparation method is basically the same as that of Example 1, except that the mesh number of the composite refiner is 100-150. The average grain size of the grain-refined nickel-based high-temperature alloy obtained in Example 2 is 2918 μm, the proportion of equiaxed crystals in the cross section is 84%, and the proportion of shrinkage porosity is 0.054%. The specific grain macrostructure photo is shown in Figure 2 As shown in a in the figure, the shrinkage and porosity statistics are as follows Figure 2 As shown in b.

[0067] Embodiment 3:

[0068] The preparation method is basically the same as that of Example 1, except that the mesh number of the composite refiner is 200-250. The average grain size of the grain-refined nickel-based high-temperature alloy obtained in Example 3 is 2186 μm, the proportion of equiaxed crystals in the cross section is 89%, and the proportion of shrinkage porosity is 0.012%. The specific grain macrostructure photo is shown in Figure 3 As shown in a in the figure, the shrinkage and porosity statistics are as follows Figure 3 As shown in b.

[0069] Embodiment 4:

[0070] The preparation method is basically the same as that of Example 1, except that the addition amount of the composite refiner is 0.2wt%. Example 4 After obtaining the grain-refined nickel-based high-temperature alloy, a surface macroscopic chemical etchant 250mL HCl+250mL H 2 O 2 Carry out corrosion and obtain the surface macroscopic corrosion map, such as Figure 6 As shown in b, 150-200#0.2wt%.

[0071] Embodiment 5:

[0072] The preparation method is basically the same as that of Example 1, except that the addition amount of the composite refiner is 0.3wt%. Example 5 After obtaining the grain-refined nickel-based high-temperature alloy, a surface macroscopic chemical etchant 250mL HCl+250mL H 2 O 2 Carry out corrosion and obtain the surface macroscopic corrosion map, such as Figure 6 As shown in b, 150-200#0.3wt%.

[0073] Embodiment 6:

[0074] The preparation method is basically the same as that of Example 2, except that the addition amount of the composite refiner is 0.2wt%. Example 6 After obtaining the grain-refined nickel-based high-temperature alloy, a surface macroscopic chemical etchant 250mL HCl+250mL H 2 O 2 Carry out corrosion and obtain the surface macroscopic corrosion map, such as Figure 6 As shown in b, 100-150#0.2wt%.

[0075] Embodiment 7:

[0076] The preparation method is basically the same as that of Example 2, except that the addition amount of the composite refiner is 0.3wt%. Example 7 After obtaining the grain-refined nickel-based high-temperature alloy, a surface macroscopic chemical etchant 250mL HCl+250mL H 2 O 2 Carry out corrosion and obtain the surface macroscopic corrosion map, such as Figure 6 As shown in b, 100-150#0.3wt%.

[0077] Embodiment 8:

[0078] The preparation method is basically the same as that of Example 3, except that the addition amount of the composite refiner is 0.2wt%. Example 8 After obtaining the grain-refined nickel-based high-temperature alloy, a surface macroscopic chemical etchant 250mL HCl+250mL H 2 O 2Carry out corrosion and obtain the surface macroscopic corrosion map, such as Figure 6 As shown in b, 200-250#0.2wt%.

[0079] Embodiment 9:

[0080] The preparation method is basically the same as that of Example 3, except that the addition amount of the composite refiner is 0.3wt%. Example 9 After obtaining the grain-refined nickel-based high-temperature alloy, a surface macroscopic chemical etchant 250mL HCl+250mL H 2 O 2 Carry out corrosion and obtain the surface macroscopic corrosion map, such as Figure 6 As shown in b, 200-250#0.3wt%.

[0081] Comparative Example 1:

[0082] The preparation method is basically the same as that of Example 1, except that no composite refiner is added. The average grain size of the nickel-based high-temperature alloy obtained in Comparative Example 1 is 6981 μm, the proportion of equiaxed crystals in the cross section is 54%, and the proportion of shrinkage porosity is 0.226%. The specific grain macrostructure photo is as follows Figure 4 As shown in a in the figure, the shrinkage and porosity statistics are as follows Figure 4 As shown in b.

[0083] according to Figure 1 to Figure 4 It can be seen that the addition of a refiner will significantly reduce the average grain size of the grain-refined nickel-based high-temperature alloy, can greatly increase the proportion of equiaxed crystals in the cross section, and at the same time reduce the proportion of shrinkage and shrinkage cavities. In addition, the mesh number of the refiner will also affect the average grain size, the proportion of equiaxed crystals in the cross section, and the proportion of shrinkage in the grain-refined nickel-based high-temperature alloy. The mesh number of the refiner in Example 1 is 150-200, and the average grain size of the nickel-based high-temperature alloy can be refined to 129μm, which is much smaller than the average grain size of the grain-refined nickel-based high-temperature alloy in Example 2 and Example 3, and the proportion of shrinkage is the lowest; it can be concluded that the grain refining effect is best when the mesh number of the refiner is 150-200.

[0084] Figure 5 This is a longitudinal cross-sectional view of the grain-refined nickel-based high-temperature alloy without adding a refiner and after adding 0.1wt% of a refiner at different mesh sizes. Figure 5 It can be further seen that the grain size and distribution of the nickel-based high-temperature alloy obtained are very different when the refiner is added or not, and when the amount of refiner added is the same and the mesh number of the refiner is different. When no refiner is added, the grain size is large and the distribution is uneven; when the amount of refiner added is 0.1wt% and the mesh number of the refiner is 150-200, the grain size is the smallest and the dispersion is uniform.

[0085] Figure 6The longitudinal section of the grain-refined nickel-based high-temperature alloy after adding different contents and mesh sizes of the refiner according to the present invention. Figure 6 It can be seen that the grains with the addition of refiners are smaller and more evenly distributed than those without the addition of refiners. When the amount of refiners added is the same, when the mesh number of the refiners is 150-200, the grain size is the smallest, the dispersion is the most even, and the grain refining effect is the best; when the mesh number of the refiners is the same, when the amount of the refiners added is 0.1wt%, the grain size is the smallest, the dispersion is the most even, and the grain refining effect is the best.

[0086] Figure 7 This is a schematic diagram of the overall experimental process. Figure 7 Among them, ① indicates adding refiner; ② indicates mixing refiner with melt; ③ indicates pouring melt into mold shell through guide tube; ④ indicates pulling out mold shell.

[0087] The embodiments described above are only descriptions of the preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a grain-refined nickel-based high-temperature alloy, comprising the following steps: Refining the nickel-based high-temperature alloy, lowering the temperature of the resulting melt to a pouring temperature, and obtaining a pouring melt; The casting melt is mixed with a refiner and cast into a heat-insulating mold shell; The heat-insulating mold shell is pulled from the hot zone to the cold zone to obtain the grain-refined nickel-based high-temperature alloy.

2. The preparation method according to claim 1, characterized in that: The nickel-based high-temperature alloy includes nickel-based high-temperature alloy IN939 or nickel-based high-temperature alloy IN718.

3. The preparation method according to claim 1 or 2, characterized in that: The refiner includes a Cr-Fe-Nb refiner and a Co-Fe-Nb refiner; the molar ratio of Cr, Fe and Nb in the Cr-Fe-Nb refiner is 1:1:1; the molar ratio of Co, Fe and Nb in the Co-Fe-Nb refiner is 3:1:2; the mass ratio of the Cr-Fe-Nb refiner to the Co-Fe-Nb refiner is 1:

1.

4. The preparation method according to claim 3, characterized in that: The mesh sizes of the Cr-Fe-Nb refiner and the Co-Fe-Nb refiner are independently 100-250 meshes; the total mass of the Cr-Fe-Nb refiner and the Co-Fe-Nb refiner is 0.1-0.3% of the mass of the nickel-based high-temperature alloy.

5. The preparation method according to claim 1, characterized in that: The pulling rate is 400-550 μm / s.

6. The preparation method according to claim 1, characterized in that: The refining temperature is 150-200° C. higher than the liquidus of the nickel-based high-temperature alloy, and the refining time is 2-3 minutes.

7. The preparation method according to claim 1, characterized in that: The pouring temperature is 40-80° C. higher than the liquidus of the nickel-based high-temperature alloy.

8. The preparation method according to claim 1, characterized in that: The temperature of the heat-insulating mold shell is the temperature between the solid-liquid phase zone of the nickel-based high-temperature alloy.

9. The grain-refined nickel-based high-temperature alloy prepared by the preparation method according to any one of claims 1 to 8, wherein the average grain size of the grain-refined nickel-based high-temperature alloy is 129 to 2918 μm, the proportion of equiaxed crystals in the cross section is 84 to 98%, and the proportion of shrinkage porosity is 0.003 to 0.054%.

10. Use of the grain-refined nickel-based high-temperature alloy according to claim 9 in aero-engine castings.

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