A nickel-based superalloy and a method of making the same

Abstract

This invention provides a method for preparing a nickel-based superalloy, relating to the field of superalloy material preparation and heat treatment technology, comprising the following steps: sequentially subjecting a nickel-based superalloy ingot to electroslag remelting, homogenization, and forging to obtain the nickel-based superalloy. In this invention, the electroslag remelting process simultaneously precipitates primary M6C carbides and primary SiC carbides. Compared to M6C, SiC is easier to precipitate and dissolve; therefore, after the primary SiC carbides consume some carbon, less primary M6C carbides are formed, thus reducing the difficulty of carbide dissolution. The homogenization process then allows the primary carbides to fully dissolve into the austenitic matrix and eliminates elemental segregation. Finally, the forging process ensures that the secondary M6C carbides reprecipitate from the matrix in a dispersed distribution, preventing the primary carbides from agglomerating in bands along the forging direction due to genetic effects, thereby avoiding damage to the alloy's strength and plasticity.

Description

Technical Field

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

[0002] Nickel-based superalloys are important structural materials in aerospace, nuclear power, petroleum, and chemical industries. The strength of nickel-based superalloys is often improved by adding alloying elements such as W, Mo, Cr, and C. However, high contents of refractory metals such as W and Mo can exacerbate element segregation during solidification and promote the precipitation of primary carbides in the interdendritic region at the end of solidification. In large ingots weighing over 100 kilograms, element segregation between dendrites and dendrite trunks is particularly significant, and the size of primary carbides is also significantly increased.

[0003] These primary carbides can be inherited into products such as plates, bars, and tubes during subsequent cold and hot working processes. Simultaneously, secondary carbides are prone to precipitate again in the dendritic regions where elemental segregation is severe. Without effective control, primary and secondary carbides can aggregate in bands along the processing direction. These banded carbide aggregates easily become preferential nucleation sites for creep cavities and microcracks, thus promoting crack initiation and propagation, severely impairing the alloy's strength and ductility. Summary of the Invention

[0004] Therefore, the present invention provides a nickel-based superalloy and its preparation method, which can solve the problem in the prior art where the strength and plasticity of the alloy are impaired due to the presence of banded aggregates of carbides.

[0005] To address the aforementioned problems, this invention provides a method for preparing a nickel-based superalloy, comprising the following steps:

[0006] Step 1): Electroslag remelting is performed on the nickel-based superalloy ingot to obtain an electroslag ingot;

[0007] In this process, after the electroslag remelting treatment, primary M6C carbide and primary SiC carbide are precipitated in the electroslag ingot.

[0008] Step 2): The electroslag ingot is homogenized to dissolve the primary M6C carbide and the primary SiC carbide, thereby obtaining a homogenized electroslag ingot.

[0009] Step 3): The electroslag ingot after homogenization is forged to precipitate and disperse secondary M6C carbides in the matrix, thereby obtaining the nickel-based high-temperature alloy.

[0010] Furthermore, the slag used in the electroslag remelting process includes: 70-85 wt.% CaF2, 10-20 wt.% CaO, and 5-15 wt.% Al2O3; and / or

[0011] During the electroslag remelting process, argon gas is introduced for protection; preferably, the flow rate of argon gas is 10~20 L / min.

[0012] Furthermore, after the forging process, the process further includes: heat treatment of the forged nickel-based superalloy; preferably, the heat treatment temperature is 1180~1220℃; and the heat treatment holding time is 30~120min.

[0013] Furthermore, the homogenization treatment temperature is 1200~1250℃; preferably, the electroslag ingot is heated to 1000℃ at a rate of 10~20℃ / min by furnace heating, and then heated to 1200~1250℃ at a rate of 3~8℃ / min; and / or

[0014] The homogenization treatment time T = T0 + K·(D-100), where T0 is the holding time of the homogenization treatment when the diameter D of the electroslag ingot is ≤100mm, which is 30~40h; K is the increment of the holding time corresponding to each 1mm increase in the diameter of the electroslag ingot, which is 0.03~0.04h / mm.

[0015] Furthermore, after the homogenization treatment, the dissolution rate of primary M6C carbide is ≥90%, and the dissolution rate of primary SiC carbide is ≥90%.

[0016] Furthermore, the forging process involves ≥3 forging cycles; the initial forging temperature for each cycle is 1175~1250℃, and the final forging temperature is ≥950℃; the total deformation during the forging process is ≥30%.

[0017] Furthermore, by mass percentage, in the ingot of the nickel-based superalloy, the content of Ni is ≥60wt%, the content of W is ≥9wt%, the content of Mo is ≥4.8wt%, the content of Cr is ≥20wt%, the content of C is ≥0.05wt%, the content of Si is ≥0.3wt%, the content of Mn is ≥0.3wt%, the content of B is ≥0.001wt%, the content of O is ≤0.001%, and the content of S is ≤0.001%.

[0018] Furthermore, the nickel-based superalloy ingot is obtained by vacuum induction melting of the raw materials;

[0019] Preferably, the vacuum induction melting process specifically includes: placing the raw material in a vacuum induction melting furnace, melting the raw material when the vacuum degree is ≤1.0Pa, and refining it at a high temperature of 1500~1600℃; wherein, the high temperature refining time is T=T0+C·(W-100); wherein, T0 is the refining time when the raw material weight W≤100kg, which is 15~40min; C is the refining time increment corresponding to each 1kg increase in raw material weight, which is 0.04~0.05 min / kg; T≤240min.

[0020] Furthermore, prior to the heat treatment step, the process further includes: rolling the forged nickel-based superalloy.

[0021] Preferably, the initial temperature of the rolling process is 1170~1230℃, the final rolling temperature is ≥950℃, and the total deformation of the rolling process is ≥50%.

[0022] On the other hand, the present invention provides a nickel-based superalloy, wherein the nickel-based superalloy is obtained by any of the preparation methods described above; the M6C carbide in the nickel-based superalloy is spherical or blocky and dispersed in the grains, and the average size of the M6C carbide is ≤3μm; the grains are equiaxed and the average size of the grains is ≤200μm.

[0023] The nickel-based superalloy has a yield strength Rp0.2≥220MPa, a tensile strength Rm≥470MPa, and an elongation A≥45% at 750℃; the nickel-based superalloy has a creep life ≥80h at 750℃ and 200MPa, and an elongation A≥45%.

[0024] The nickel-based superalloy and its preparation method provided by this invention have the following beneficial effects:

[0025] 1. On one hand, the present invention provides a method for preparing a nickel-based superalloy, comprising the following steps: electroslag remelting of a nickel-based superalloy ingot to obtain an electroslag ingot; then homogenizing the electroslag ingot to obtain a homogenized electroslag ingot; and forging the homogenized electroslag ingot to precipitate and disperse secondary M6C carbides in the matrix, thereby obtaining the nickel-based superalloy. This invention utilizes electroslag remelting to simultaneously precipitate primary M6C carbides and primary SiC carbides. Compared to M6C, SiC is easier to precipitate and dissolve. Therefore, after the primary SiC carbides consume some of the carbon, less primary M6C carbides are formed, thus reducing the difficulty of carbide dissolution. A homogenization process further ensures the primary carbides are fully dissolved into the austenitic matrix and eliminates elemental segregation. Finally, forging ensures that the secondary M6C carbides reprecipitate from the matrix in a dispersed distribution, preventing the primary carbides from agglomerating in bands along the forging direction due to genetic effects, thereby avoiding damage to the alloy's strength and plasticity.

[0026] 2. Furthermore, while ensuring uniform carbide distribution in the alloy, the thermal activation energy is increased by controlling the heat treatment temperature (1180~1220℃). This enhanced thermal activation effect promotes grain boundary migration, thereby weakening the hindering effect of M6C on grain boundary migration and avoiding the mixed-grain structure caused by uneven M6C distribution, which results in the coexistence of coarse and fine grains. This achieves uniform growth of equiaxed grains. Simultaneously, by controlling the holding time of the heat treatment (30~120 min), the grain size of the equiaxed grains is controlled, resulting in an equiaxed grain structure with an average grain size not exceeding 200 μm and a uniform size distribution. This gives the alloy both excellent strength and plasticity.

[0027] 3. On the other hand, the present invention provides a nickel-based superalloy, which is obtained by any of the preparation methods described above; the M6C carbides in the nickel-based superalloy are spherical or blocky and dispersed within the grains; the grains are equiaxed and the average grain size is ≤200μm. This nickel-based superalloy has high high-temperature strength and plasticity, meeting the requirements of practical applications. Specifically, the nickel-based superalloy has a yield strength Rp0.2≥220MPa, a tensile strength Rm≥470MPa, and an elongation A≥45% at 750℃; the nickel-based superalloy has a creep life ≥80h and an elongation A≥45% under conditions of 750℃ and 200MPa. Attached Figure Description

[0028] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0029] Figure 1 This is an electron probe microanalysis image of the microstructure in the ingot of the nickel-based superalloy from Example 1.

[0030] Figure 2 Electron probe microanalysis of the microstructure in the electroslag ingot of Example 1;

[0031] Figure 3 This is an electron probe microanalysis image of the microstructure of the electroslag ingot after homogenization treatment in Example 1.

[0032] Figure 4 Here is a scanning electron microscope image of the microstructure of the alloy in Example 1 after hot rolling.

[0033] Figure 5 This is an electron probe microanalysis image of the microstructure of the alloy in Example 1 after heat treatment;

[0034] Figure 6 The images show the microstructure of the alloy ingot in Comparative Example 1 after homogenization, hot rolling, and heat treatment.

[0035] Figure 7 This is a comparison chart showing the dissolution ratio of the primary M6C carbide after homogenization treatment and the average size of the secondary M6C carbide after heat treatment in Example 1 and Comparative Example 1.

[0036] Figure 8 The images show the metallographic and scanning electron microscope (SEM) images of the microstructure of alloy 2 after hot rolling.

[0037] Figure 9 Metallographic images of the microstructure of alloys in Examples 1-3 after heat treatment;

[0038] Figure 10 Metallographic images of the microstructure of alloys 2-5 after heat treatment;

[0039] Figure 11 This is a comparison diagram of the average grain size of Examples 1-3 and Comparative Example 3 after heat treatment;

[0040] Figure 12 The graph shows a comparison of the yield strength and tensile strength of Examples 1-3 and Comparative Example 3 after heat treatment at 750°C.

[0041] Figure 13This is a comparison chart of the creep life of Examples 1 and 2 and Comparative Examples 2, 4 and 5 after heat treatment at 750℃ / 200MPa. Detailed Implementation

[0042] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the specific embodiments, structures, features, and effects according to the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. In the following description, different "an embodiment" or "an embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0043] The applicant also discovered that during processing, fine equiaxed grains are formed through dynamic recrystallization. These grains can gradually grow during heat treatment, which helps to adjust to a suitable grain size. During heat treatment, primary and secondary carbides hinder grain boundary migration. In regions where carbides are distributed in a banded pattern, grain boundary migration is significantly suppressed, resulting in smaller grain sizes in these regions; while in regions with fewer or no carbides, grain boundary migration resistance is lower, and grains grow easily and are larger. This uneven grain size distribution forms a mixed-grain structure. Under external loads, the fine-grained regions, due to their high grain boundary density and large number of carbides, are prone to stress concentration, reducing the deformation compatibility with adjacent large grains, thereby promoting crack initiation and propagation, and severely impairing the mechanical properties of the alloy. Therefore, the present invention is proposed, specifically as follows:

[0044] On one hand, the present invention provides a method for preparing a nickel-based superalloy, comprising the following steps:

[0045] Step 1): Electroslag remelting is performed on the nickel-based superalloy ingot to obtain an electroslag ingot;

[0046] Among them, after electroslag remelting, primary M6C carbide and primary SiC carbide are precipitated in the electroslag ingot;

[0047] Step 2): Homogenize the electroslag ingot to dissolve the primary M6C carbide and primary SiC carbide, and obtain the homogenized electroslag ingot.

[0048] Step 3): The electroslag ingot after homogenization is forged to precipitate and disperse secondary M6C carbides in the matrix, thus obtaining a nickel-based high-temperature alloy.

[0049] This invention utilizes electroslag remelting to simultaneously precipitate primary M6C carbides and primary SiC carbides. Compared to M6C, SiC is easier to precipitate and dissolve. Therefore, after the primary SiC carbides consume some of the carbon, fewer primary M6C carbides are formed, thus reducing the difficulty of carbide dissolution. A homogenization process further ensures the primary carbides are fully dissolved into the austenitic matrix. Finally, forging ensures that the secondary M6C carbides reprecipitate from the matrix in a dispersed distribution, preventing the primary carbides from agglomerating in bands along the forging direction due to genetic effects, thereby avoiding damage to the alloy's strength and plasticity.

[0050] In some embodiments, the slag used in the above-mentioned electroslag remelting process includes: 70-85 wt.% CaF2, 10-20 wt.% CaO, and 5-15 wt.% Al2O3; during the electroslag remelting process, argon gas is introduced for protection; preferably, the argon gas flow rate is 10-20 L / min. The alloy ingot is used as the electrode for electroslag remelting. The high-temperature slag gradually melts the ingot electrode. Argon gas protection prevents oxygen and nitrogen from entering the molten metal and forming inclusions. The rapid solidification after the electrode gradually melts reduces elemental segregation and promotes the dispersion and precipitation of fine primary SiC carbides in the austenitic matrix. Since SiC consumes a portion of the C content in the alloy, the amount of primary M6C carbides in the electroslag ingot is reduced compared to that in the cast ingot.

[0051] In some embodiments, after the forging process, the process further includes: heat treatment of the forged nickel-based superalloy; preferably, the heat treatment temperature is 1180~1220℃; and the holding time is 30~120min. While ensuring uniform carbide distribution in the alloy, the heat treatment temperature is controlled to increase the thermal activation energy. This enhanced thermal activation effect promotes grain boundary migration, thereby weakening the hindering effect of M6C on grain boundary migration and avoiding a mixed-grain structure caused by uneven M6C distribution, resulting in coarse and fine grains. This achieves uniform growth of equiaxed grains. It avoids the mixed-grain structure caused by excessively low temperatures, while preventing excessively high temperatures from causing excessively large grain sizes. Simultaneously, by controlling the holding time of the heat treatment, the grain size of the equiaxed grains is regulated, resulting in an equiaxed grain structure with an average grain size not exceeding 200μm and a uniform size distribution.

[0052] In some embodiments, the homogenization treatment temperature is 1200~1250℃; preferably, the electroslag ingot is heated to 1000℃ at a rate of 10~20℃ / min by furnace heating, and then heated to 1200~1250℃ at a rate of 3~8℃ / min; the homogenization treatment time is T=T0+K·(D-100), where T0 is the holding time for homogenization treatment when the diameter of the electroslag ingot D≤100mm, which is 30~40h; K is the increment of holding time corresponding to each 1mm increase in the diameter of the electroslag ingot, which is 0.03~0.04h / mm. Through homogenization treatment, the primary M6C carbide and primary SiC carbide are fully dissolved into the austenitic matrix, and element segregation is eliminated, achieving homogenization of matrix composition. This creates conditions for the uniform precipitation of secondary carbides and avoids the decrease in alloy plasticity due to stress concentration in the segregation zone.

[0053] Furthermore, after homogenization treatment, the dissolution rate of primary M6C carbide is ≥90%, and the dissolution rate of primary SiC carbide is ≥90%.

[0054] In some embodiments, the forging process involves ≥3 forging passes; the initial forging temperature for each pass is 1175~1250℃, and the final forging temperature is ≥950℃; the total deformation of the forging process is ≥30%. Forging allows for sufficient dynamic recrystallization of the alloy, forming fine equiaxed grains, which in turn leads to a dispersed distribution of secondary M6C carbides. If dynamic recrystallization is insufficient, coarser grains exist, and secondary M6C carbides are more difficult to precipitate within these coarse grains.

[0055] Furthermore, by mass percentage, in the nickel-based superalloy ingot, the content of Ni is ≥60wt%, W is ≥9wt%, Mo is ≥4.8wt%, Cr is ≥20wt%, C is ≥0.05wt%, Si is ≥0.3wt%, Mn is ≥0.3wt%, B is ≥0.001wt%, O is ≤0.001%, and S is ≤0.001%.

[0056] In some embodiments, nickel-based superalloy ingots are obtained by vacuum induction melting of raw materials. Specifically, this includes: placing the raw materials in a vacuum induction melting furnace, melting the raw materials when the vacuum degree is ≤1.0 Pa, and refining them at 1500~1600℃; wherein the high-temperature refining time is T=T0+C·(W-100); where T0 is the refining time when the raw material weight W≤100kg, which is 15~40min; C is the refining time increment corresponding to each 1kg increase in raw material weight, which is 0.04~0.05 min / kg; T≤240min. Vacuum induction melting completely melts the raw materials and effectively removes impurity elements. Significant element segregation occurs during the slow solidification process of the ingot, and M6C carbides also precipitate between dendrites.

[0057] In some embodiments, prior to the heat treatment step, the process further includes: rolling the forged nickel-based superalloy; preferably, the initial rolling temperature is 1170~1230℃, the final rolling temperature is ≥950℃, and the total deformation of the rolling process is ≥50%. Through rolling, accurate control of the plate dimensions is achieved.

[0058] On the other hand, the present invention provides a nickel-based superalloy, which is obtained by any of the above preparation methods; the M6C carbides in the nickel-based superalloy are spherical or blocky and dispersed within the grains; the grains are equiaxed and the average grain size is ≤200μm; wherein, the nickel-based superalloy has a yield strength Rp0.2≥220MPa, a tensile strength Rm≥470MPa, and an elongation A≥45% at 750℃; the nickel-based superalloy has a creep life ≥80h and an elongation A≥45% under the conditions of 750℃ and 200MPa.

[0059] The present invention will be further described below with reference to specific embodiments and comparative examples.

[0060] Example 1

[0061] This embodiment provides a method for preparing a high-tungsten, high-molybdenum nickel-based superalloy. The raw materials for this nickel-based superalloy, by mass percentage, are: Cr 22wt%, W 9wt%, Mo 5wt%, C 0.06wt%, Mn 0.5wt%, Si 0.35wt%, B 0.004wt%, with the balance being Ni. The method specifically includes the following steps:

[0062] Step 1): Place 100kg of raw material in a vacuum induction melting furnace. When the vacuum degree is ≤1.0Pa, energize the induction coil to completely melt the raw material. Then, refine the molten metal at 1550℃ for 40 minutes and cast it into an ingot with a diameter of about 140mm. The 40min high-temperature refining time is calculated according to T=T0+C·(W-100), where W is 100kg and T0 is 40min.

[0063] After removing the riser of the above alloy ingot, the ingot is used as the metal electrode. Using slag containing 80wt.%CaF2, 10wt.%CaO and 10wt.%Al2O3, and protected by argon gas with an argon flow rate of 15L / min, an electroslag ingot with a diameter of 170mm is obtained.

[0064] Step 2): After removing the riser of the electroslag ingot, place it in a heat treatment furnace and heat it up with the furnace. The heating rate from room temperature to 1000℃ is 15℃ / min, and the heating rate from 1000℃ to 1200℃ is 5℃ / min. Hold it at 1200℃ for 34 hours for homogenization treatment. After the holding period, remove it from the furnace and air cool it to room temperature. The homogenization treatment time of 34 hours is calculated according to T=T0+K·(D-100), where D is 170mm, T0 is 31.2h, and K is 0.04h / mm.

[0065] Step 3): The electroslag ingot after the above homogenization treatment is subjected to three forging processes. The initial forging temperature of each process is 1200℃, and the final forging temperature is not lower than 950℃. The deformation amount of each forging process is about 20%, and the total deformation amount is 60%. After forging, the ingot is air-cooled to room temperature.

[0066] The forgings obtained after the above forging process are subjected to rolling treatment. The initial rolling temperature is 1180℃, the final rolling temperature is ≥950℃, the total deformation of the rolling process is about 70%, and the forgings are air-cooled to room temperature after rolling treatment.

[0067] Samples were cut from the hot-rolled sheet and subjected to heat treatment at 1210℃ for 60 minutes.

[0068] Table 1 shows the measured chemical composition of the ingot and the electroslag ingot in Example 1. The table shows that vacuum induction melting achieved lower O and S content in the ingot, and electroslag remelting technology can further reduce the S content in the alloy.

[0069] Table 1. Measured chemical composition of ingots and electroslag ingots in Example 1 (unit: wt.%)

[0070]

[0071] Figure 1 This is an electron probe microanalysis image of the microstructure of the alloy vacuum induction ingot (cast ingot) in this embodiment. As can be seen from the image, the alloying elements in the ingot exhibit obvious dendritic segregation characteristics. Among them, the concentration of Ni element is higher in the dendrite trunk, and the concentration of Cr, W, Mo, and C elements is higher in the interdendritic region. Furthermore, blocky or granular primary M6C carbides precipitate from the austenite matrix. These carbides are rich in Mo and C and are mainly distributed in the interdendritic region.

[0072] Figure 2 This is an electron probe micrograph of the microstructure of the electroslag ingot in this embodiment. As can be seen from the figure, the alloying elements in the electroslag ingot also exhibit a certain degree of dendritic segregation, but its segregation degree is lower than that of the cast ingot. Figure 1In the interdendritic regions of the electroslag ingot, blocky or granular primary M6C carbides rich in Mo and C also precipitate. In particular, after electroslag remelting, fine, dispersed primary SiC carbides rich in Si and C are newly precipitated in the alloy.

[0073] Figure 3 This is an electron probe microanalysis image of the microstructure of the electroslag ingot after high-temperature homogenization treatment in this embodiment. As can be seen from the image, after high-temperature homogenization, the dendritic features are almost completely eliminated, and the distribution of each alloying element in the austenitic matrix is ​​relatively uniform, with no obvious element enrichment observed. Simultaneously, the primary M6C carbide in the electroslag ingot is almost completely dissolved back into the matrix, and most of the primary SiC carbide is also dissolved back into the matrix, with dissolution ratios of approximately 98% and 93%, respectively. The results indicate that high-temperature homogenization treatment can effectively eliminate element segregation and promote the dissolution of primary carbides.

[0074] Figure 4 The image shows a scanning electron microscope (SEM) image of the microstructure of the alloy after hot rolling in this embodiment. As can be seen from the image, the secondary M6C carbides in the hot-rolled sheet do not show obvious aggregation, whether parallel or perpendicular to the hot rolling direction. They are distributed relatively discretely in the matrix, and the equiaxed grains are uniform and fine, with an average grain size of 13 μm.

[0075] Figure 5 This is an electron probe microanalysis image of the alloy microstructure after heat treatment in this embodiment. As can be seen from the image, after heat treatment, the secondary M6C carbides remain dispersed in the austenite matrix, with an average size of approximately 1.5 μm, indicating that they did not dissolve during the heat treatment process and can hinder grain boundary migration. The primary SiC carbides, however, are almost completely dissolved in the matrix, and no re-precipitation was observed; moreover, fine granular M6C carbides precipitate at the grain boundaries. 23 C6 carbides, these grain boundary carbides, can strengthen grain boundaries by hindering dislocation movement.

[0076] Example 2

[0077] This embodiment provides a method for preparing a high-tungsten, high-molybdenum nickel-based superalloy. The raw materials for this nickel-based superalloy, by mass percentage, are: Cr 22wt%, W 9wt%, Mo 5wt%, Mn 0.5wt%, Si 0.35wt%, C 0.06wt%, B 0.004wt%, with the balance being Ni. The method specifically includes the following steps:

[0078] Step 1): Place 100kg of raw material in a vacuum induction melting furnace. When the vacuum degree is ≤1.0Pa, energize the induction coil to completely melt the raw material. Then, refine the molten metal at 1550℃ for 40 minutes and cast it into an ingot with a diameter of about 140mm. The 40min high-temperature refining time is calculated according to T=T0+C·(W-100), where W is 100kg and T0 is 40min.

[0079] After removing the riser of the above alloy ingot, the ingot is used as the metal electrode. Using slag containing 80wt.%CaF2, 10wt.%CaO and 10wt.%Al2O3, and protected by argon gas with an argon flow rate of 15L / min, an electroslag ingot with a diameter of 170mm is obtained.

[0080] Step 2): After removing the riser of the electroslag ingot, place it in a heat treatment furnace and heat it up with the furnace. The heating rate from room temperature to 1000℃ is 15℃ / min, and the heating rate from 1000℃ to 1200℃ is 5℃ / min. Hold it at 1200℃ for 34 hours for homogenization treatment. After the holding period, remove it from the furnace and air cool it to room temperature. The homogenization treatment time of 34 hours is calculated according to T=T0+K·(D-100), where D is 170mm, T0 is 31.2h, and K is 0.04h / mm.

[0081] Step 3): The electroslag ingot after the above homogenization treatment is subjected to three forging processes. The initial forging temperature of each process is 1200℃, and the final forging temperature is not lower than 950℃. The deformation amount of each forging process is about 20%, and the total deformation amount is 60%. After forging, the ingot is air-cooled to room temperature.

[0082] The forgings obtained after the above forging process are subjected to rolling treatment. The initial rolling temperature is 1180℃, the final rolling temperature is ≥950℃, the total deformation of the rolling process is about 70%, and the forgings are air-cooled to room temperature after rolling treatment.

[0083] Samples were cut from the hot-rolled sheet and subjected to heat treatment at 1190℃ for 60 minutes.

[0084] Example 3

[0085] This embodiment provides a method for preparing a high-tungsten, high-molybdenum nickel-based superalloy. The raw materials for this nickel-based superalloy, by mass percentage, are: Cr 22wt%, W 9wt%, Mo 5wt%, C 0.06wt%, Mn 0.5wt%, Si 0.35wt%, B 0.004wt%, with the balance being Ni. The method specifically includes the following steps:

[0086] Step 1): Place 100kg of raw material in a vacuum induction melting furnace. When the vacuum degree is ≤1.0Pa, energize the induction coil to completely melt the raw material. Then, refine the molten metal at 1550℃ for 40 minutes and cast it into an ingot with a diameter of about 140mm. The 40min high-temperature refining time is calculated according to T=T0+C·(W-100), where W is 100kg and T0 is 40min.

[0087] After removing the riser of the above alloy ingot, the ingot is used as the metal electrode. Using slag containing 80wt.%CaF2, 10wt.%CaO and 10wt.%Al2O3, and protected by argon gas with an argon flow rate of 15L / min, an electroslag ingot with a diameter of 170mm is obtained.

[0088] Step 2): After removing the riser of the electroslag ingot, place it in a heat treatment furnace and heat it up with the furnace. The heating rate from room temperature to 1000℃ is 15℃ / min, and the heating rate from 1000℃ to 1200℃ is 5℃ / min. Hold it at 1200℃ for 34 hours for homogenization treatment. After the holding period, remove it from the furnace and air cool it to room temperature. The homogenization treatment time is 34 hours, which is calculated according to T=T0+K·(D-100), where D is 170mm, T0 is 31.2h, and K is 0.04h / mm.

[0089] Step 3): The electroslag ingot after the above homogenization treatment is subjected to three forging processes. The initial forging temperature of each process is 1200℃, and the final forging temperature is not lower than 950℃. The deformation amount of each forging process is about 20%, and the total deformation amount is 60%. After forging, the ingot is air-cooled to room temperature.

[0090] The forgings obtained after the above forging process are subjected to rolling treatment. The initial rolling temperature is 1180℃, the final rolling temperature is ≥950℃, the total deformation of the rolling process is about 70%, and the forgings are air-cooled to room temperature after rolling treatment.

[0091] Samples were cut from the hot-rolled sheet and subjected to heat treatment at 1210℃ for 30 minutes.

[0092] Comparative Example 1

[0093] This comparative example provides a method for preparing a high-tungsten, high-molybdenum nickel-based superalloy. The measured chemical composition of the nickel-based superalloy ingot, by mass percentage, includes: Cr 21.9 wt%, W 9.48 wt%, Mo 5.05 wt%, Mn 0.52 wt%, Si 0.36 wt%, C 0.095 wt%, B 0.004 wt%, O 0.0004 wt%, S < 0.0005 wt%, with the balance being Ni. The method specifically includes the following steps:

[0094] Step 1): Place 10 kg of raw material in a vacuum induction melting furnace. When the vacuum degree is ≤1.0 Pa, energize the induction coil to completely melt the raw material. Then, refine the molten metal at 1520℃ for 20 min and cast it into an ingot with a diameter of about 85 mm. The 20 min of high-temperature refining time is calculated according to T=T0+C·(W-100), where W is 10 kg and T0 is 20 min.

[0095] Step 2): After removing the riser from the ingot, place it in a heat treatment furnace and heat it up with the furnace. The heating rate from room temperature to 1000℃ is 15℃ / min, and the heating rate from 1000℃ to 1200℃ is 5℃ / min. Hold it at 1200℃ for 34 hours for homogenization treatment. After holding, remove it from the furnace and air cool it to room temperature. The homogenization treatment time of 34 hours is calculated according to T=T0+K·(D-100), where D is 170mm, T0 is 31.2h, and K is 0.04h / mm.

[0096] Step 3): The ingot that has undergone the above homogenization treatment is subjected to three forging processes. The initial forging temperature of each process is 1200℃, and the final forging temperature is not lower than 950℃. The deformation amount of each forging process is about 20%, and the total deformation amount is 60%. After forging, the ingot is air-cooled to room temperature.

[0097] Step 4): The forging obtained after the above forging process is rolled. The initial rolling temperature is 1180℃, the final rolling temperature is ≥950℃, the total deformation of the rolling process is 70%, and the forging is air-cooled to room temperature after rolling.

[0098] Step 5): Cut a sample from the hot-rolled plate and heat-treat the sample at a temperature of 1210℃ for 60 minutes.

[0099] Figure 6 These are scanning electron microscope (SEM) images of the microstructure of the alloy ingot in this comparative example, after high-temperature homogenization, rolling, and heat treatment. The alloy was not prepared via electroslag remelting; instead, the ingot underwent direct high-temperature homogenization. The images show that only primary M6C carbides were observed in the ingot. Although the size of the primary M6C carbides decreased after high-temperature homogenization, dissolution was incomplete, with a dissolution rate of approximately 50%. After rolling, the M6C carbides still exhibited a banded distribution along the hot-working direction; this distribution pattern was maintained after heat treatment, with an average M6C carbide size of approximately 3.5 μm. Figure 7The dissolution ratio of primary M6C carbides after high-temperature homogenization treatment and the average size of secondary M6C carbides after heat treatment were compared between Example 1 and Comparative Example 1. The results showed that the dissolution ratio of primary M6C carbides after high-temperature homogenization in Example 1, which underwent electroslag remelting, was significantly higher than that in Comparative Example 1, which did not undergo electroslag remelting. Furthermore, the average size of secondary M6C carbides obtained by Example 1 after heat treatment using the preparation method of this invention was smaller than that in Comparative Example 1. These results indicate that the electroslag remelting step of this invention is crucial: the ingot electrode is gradually melted using high-temperature slag, and oxygen and nitrogen are prevented from entering the molten metal and forming inclusions under argon protection; the rapid solidification after the electrode is gradually melted can reduce elemental segregation and promote the dispersion and precipitation of fine primary SiC carbides in the austenitic matrix. Since SiC consumes some of the C content in the alloy, the amount of primary M6C carbides in the electroslag ingot is reduced compared to the cast ingot, which is key to ensuring sufficient dissolution of carbides during the high-temperature homogenization process.

[0100] Comparative Example 2

[0101] This comparative example provides a method for preparing a high-tungsten, high-molybdenum nickel-based superalloy. The measured chemical composition of the nickel-based superalloy ingot, by mass percentage, includes: Cr 21.9 wt%, W 9.0 wt%, Mo 4.97 wt%, Mn 0.5 wt%, Si 0.35 wt%, C 0.067 wt%, B 0.004 wt%, N < 0.0003 wt%, O 0.0008 wt%, S < 0.0005 wt%, with the balance being Ni. The method specifically includes the following steps:

[0102] Step 1): Place 10 kg of raw material in a vacuum induction melting furnace. When the vacuum degree is ≤1.0 Pa, energize the induction coil to completely melt the raw material. Then, refine the molten metal at 1520℃ for 20 min and cast it into an ingot with a diameter of about 85 mm. The 20 min of high-temperature refining time is calculated according to T=T0+C·(W-100), where W is 10 kg and T0 is 20 min.

[0103] Step 2): After removing the riser of the ingot, perform three forging processes. The initial forging temperature of each process is 1200℃, and the final forging temperature is not lower than 950℃. The deformation amount of each forging process is about 20%, and the total deformation amount is 60%. After forging, air cool to room temperature. The homogenization time of 34h is calculated according to T=T0+K·(D-100), where D is 170mm, T0 is 31.2h, and K is 0.04h / mm.

[0104] Step 3): The forging obtained after the above forging process is rolled. The initial rolling temperature is 1180℃, the final rolling temperature is ≥950℃, the total deformation of the rolling process is about 70%, and the forging is air-cooled to room temperature after rolling.

[0105] Step 4): Cut a sample from the hot-rolled sheet and heat-treat the sample at a temperature of 1210℃ for 60 minutes.

[0106] Figure 8 These are metallographic and scanning electron microscope images of the microstructure of the comparative alloy after hot rolling. From Figure 8 As can be seen, in alloy plates that have not undergone electroslag remelting and high-temperature homogenization treatment, M6C carbides are aggregated along the hot working direction. The results of the examples and comparative studies show that the preparation method provided by this invention can prevent carbides from agglomerating and precipitating along the processing direction, resulting in a more dispersed distribution of carbides in the matrix.

[0107] Comparative Example 3

[0108] This comparative example provides a method for preparing a high-tungsten, high-molybdenum nickel-based superalloy. The raw material configuration for this nickel-based superalloy, by mass percentage, is: Cr 22wt%, W 9wt%, Mo 5wt%, Mn 0.5wt%, Si 0.35wt%, C 0.06wt%, B 0.004wt%, with the balance being Ni. The method specifically includes the following steps:

[0109] Step 1): Place 100kg of raw material in a vacuum induction melting furnace. When the vacuum degree is ≤1.0Pa, energize the induction coil to completely melt the raw material. Then, refine the molten metal at 1550℃ for 40 minutes and cast it into an ingot with a diameter of about 140mm. The 40min high-temperature refining time is calculated according to T=T0+C·(W-100), where W is 100kg and T0 is 40min.

[0110] After removing the riser of the above alloy ingot, the ingot is used as the metal electrode. Using slag containing 80wt.%CaF2, 10wt.%CaO and 10wt.%Al2O3, and protected by argon gas with an argon flow rate of 15L / min, an electroslag ingot with a diameter of 170mm is obtained.

[0111] Step 2): After removing the riser of the electroslag ingot, place it in a heat treatment furnace and heat it up with the furnace. The heating rate from room temperature to 1000℃ is 15℃ / min, and the heating rate from 1000℃ to 1200℃ is 5℃ / min. Hold it at 1200℃ for 34 hours for homogenization treatment. After the holding period, remove it from the furnace and air cool it to room temperature. The homogenization treatment time of 34 hours is calculated according to T=T0+K·(D-100), where D is 170mm, T0 is 31.2h, and K is 0.04h / mm.

[0112] Step 3): The electroslag ingot after the above homogenization treatment is subjected to three forging processes. The initial forging temperature of each process is 1200℃, and the final forging temperature is not lower than 950℃. The deformation amount of each forging process is about 20%, and the total deformation amount is 60%. After forging, the ingot is air-cooled to room temperature.

[0113] The forgings obtained after the above forging process are subjected to rolling treatment. The initial rolling temperature is 1180℃, the final rolling temperature is ≥950℃, the total deformation of the rolling process is about 70%, and the forgings are air-cooled to room temperature after rolling treatment.

[0114] Samples were cut from the hot-rolled sheet and subjected to heat treatment at 1230°C for 60 minutes.

[0115] Comparative Example 4

[0116] This comparative example provides a method for preparing a high-tungsten, high-molybdenum nickel-based superalloy. The raw material configuration for this nickel-based superalloy, by mass percentage, is: Cr 22wt%, W 9wt%, Mo 5wt%, Mn 0.5wt%, Si 0.35wt%, C 0.06wt%, B 0.004wt%, with the balance being Ni. The method specifically includes the following steps:

[0117] Step 1): Place 100kg of raw material in a vacuum induction melting furnace. When the vacuum degree is ≤1.0Pa, energize the induction coil to completely melt the raw material. Then, refine the molten metal at 1550℃ for 40 minutes and cast it into an ingot with a diameter of about 140mm. The 40min high-temperature refining time is calculated according to T=T0+C·(W-100), where W is 100kg and T0 is 40min.

[0118] After removing the riser of the above alloy ingot, the ingot is used as the metal electrode. Using slag containing 80wt.%CaF2, 10wt.%CaO and 10wt.%Al2O3, and protected by argon gas with an argon flow rate of 15L / min, an electroslag ingot with a diameter of 170mm is obtained.

[0119] Step 2): After removing the riser of the electroslag ingot, place it in a heat treatment furnace and heat it up with the furnace. The heating rate from room temperature to 1000℃ is 15℃ / min, and the heating rate from 1000℃ to 1200℃ is 5℃ / min. Hold it at 1200℃ for 34 hours for homogenization treatment. After the holding period, remove it from the furnace and air cool it to room temperature. The homogenization treatment time of 34 hours is calculated according to T=T0+K·(D-100), where D is 170mm, T0 is 31.2h, and K is 0.04h / mm.

[0120] Step 3): The electroslag ingot after the above homogenization treatment is subjected to three forging processes. The initial forging temperature of each process is 1200℃, and the final forging temperature is not lower than 950℃. The deformation amount of each forging process is about 20%, and the total deformation amount is 60%. After forging, the ingot is air-cooled to room temperature.

[0121] The forgings obtained after the above forging process are subjected to rolling treatment. The initial rolling temperature is 1180℃, the final rolling temperature is ≥950℃, the total deformation of the rolling process is about 70%, and the forgings are air-cooled to room temperature after rolling treatment.

[0122] Samples were cut from the hot-rolled sheet and subjected to heat treatment at 1170℃ for 60 minutes.

[0123] Comparative Example 5

[0124] This comparative example provides a method for preparing a high-tungsten, high-molybdenum nickel-based superalloy. The raw material configuration for this nickel-based superalloy, by mass percentage, is: Cr 22wt%, W 9wt%, Mo 5wt%, Mn 0.5wt%, Si 0.35wt%, C 0.06wt%, B 0.004wt%, with the balance being Ni. The method specifically includes the following steps:

[0125] Step 1): Place 100kg of raw material in a vacuum induction melting furnace. When the vacuum degree is ≤1.0Pa, energize the induction coil to completely melt the raw material. Then, refine the molten metal at 1550℃ for 40 minutes and cast it into an ingot with a diameter of about 140mm. The 40min high-temperature refining time is calculated according to T=T0+C·(W-100), where W is 100kg and T0 is 40min.

[0126] After removing the riser of the above alloy ingot, the ingot is used as the metal electrode. Using slag containing 80wt.%CaF2, 10wt.%CaO and 10wt.%Al2O3, and protected by argon gas with an argon flow rate of 15L / min, an electroslag ingot with a diameter of 170mm is obtained.

[0127] Step 2): After removing the riser of the electroslag ingot, place it in a heat treatment furnace and heat it up with the furnace. The heating rate from room temperature to 1000℃ is 15℃ / min, and the heating rate from 1000℃ to 1200℃ is 5℃ / min. Hold it at 1200℃ for 34 hours for homogenization treatment. After the holding period, remove it from the furnace and air cool it to room temperature. The homogenization treatment time of 34 hours is calculated according to T=T0+K·(D-100), where D is 170mm, T0 is 31.2h, and K is 0.04 h / mm.

[0128] Step 3): The electroslag ingot after the above homogenization treatment is subjected to three forging processes. The initial forging temperature of each process is 1200℃, and the final forging temperature is not lower than 950℃. The deformation amount of each forging process is about 20%, and the total deformation amount is 60%. After forging, the ingot is air-cooled to room temperature.

[0129] The forgings obtained after the above forging process are subjected to rolling treatment. The initial rolling temperature is 1180℃, the final rolling temperature is ≥950℃, the total deformation of the rolling process is about 70%, and the forgings are air-cooled to room temperature after rolling treatment.

[0130] Samples were cut from the hot-rolled sheet and subjected to heat treatment at 1150℃ for 60 minutes.

[0131] Figure 9 These are metallographic images of the microstructure of alloys from Examples 1-3 after heat treatment. From... Figure 9 It can be seen that after heat treatment using the method designed in this invention, the equiaxed grains in the alloy are uniform in size, which can avoid the mixed grain phenomenon of coarse and fine grains. The average grain sizes of the equiaxed grains in the alloys of Examples 1-3 after heat treatment are 150 μm, 115 μm and 125 μm, respectively, and the M6C carbide is relatively dispersed in the matrix, with no obvious carbide aggregation observed.

[0132] Figure 10 These are metallographic photographs of the microstructure of alloys 2-5 after heat treatment. Figure 10 It can be seen that the heat treatment temperature used in Comparative Example 3 is higher than that of the present invention. Grain boundaries migrate easily at high temperatures, leading to a significant increase in alloy grain size, with an average grain size of approximately 300 μm. The heat treatment temperatures used in Comparative Examples 4 and 5 are lower than those of the present invention, resulting in insufficient thermal activation and the appearance of noticeably coarse grains in some areas (e.g., ...). Figure 10(As shown in the dashed box), while other areas are still dominated by fine grains, forming a mixed crystalline structure where coarse and fine grains coexist. Therefore, too low a heat treatment temperature will result in a mixed crystalline structure where coarse and fine grains coexist; too high a heat treatment temperature will result in excessively large grain sizes. Using the heat treatment temperature of this invention, through a suitable thermal activation effect, it is possible to promote uniform migration of grain boundaries, thereby obtaining an equiaxed crystalline structure with a uniform size distribution; furthermore, through a reasonable holding time, the average grain size of the equiaxed grains can be kept below 200 μm. In Comparative Example 2, the alloy was not subjected to electroslag remelting and high-temperature homogenization treatment during preparation. The M6C carbides in the hot-rolled alloy sheet microstructure were distributed in a banded pattern along the hot working direction (see...). Figure 8 Even with the heat treatment of this invention, the banded aggregation phenomenon of M6C carbides still cannot be resolved. Figure 11 The average grain size of Examples 1-3 and Comparative Example 3 after heat treatment was compared. The results show that the average grain size of Examples 1-3 using the heat treatment method of the present invention is controlled below 200 μm. In summary, the preparation and heat treatment methods provided by the present invention can prevent carbide agglomeration and precipitation along the processing direction, promote uniform growth of equiaxed grains, avoid or reduce the mixed crystal phenomenon of coexistence of coarse and fine grains, and control the average grain size within 200 μm.

[0133] This invention provides a method for preparing and heat-treating high-tungsten, high-molybdenum, nickel-based high-temperature alloy plates. After heat treatment, the alloy plate exhibits equiaxed grains with uniform grain size and an average grain size ≤200 μm. Secondary M6C carbides are spherical or blocky, dispersed within the grains, and have an average size ≤3 μm (see...). Figure 5 and Figure 9 This gives the alloy both excellent high-temperature strength and ductility: at 750℃, the yield strength Rp0.2 ≥ 220 MPa, the tensile strength Rm ≥ 470 MPa, and the elongation A ≥ 45%; the creep life at 750℃ and 200 MPa is ≥ 80 hours, and the elongation A ≥ 45% (see Tables 2-3 below). Figures 12-13 ).

[0134] Table 2 Instantaneous tensile properties of the alloys after heat treatment in the examples and comparative examples at 750°C

[0135]

[0136] Table 3. Creep properties of alloys from the Examples and Comparative Examples after heat treatment at 750°C and 200 MPa.

[0137]

[0138] After heat treatment, the equiaxed grain size of alloy 3 in Comparative Example 3 is relatively large. Figure 10The average grain size is approximately 300 μm. Due to the excessively large grain size weakening the grain-refining strengthening effect, the high-temperature tensile yield strength and tensile strength of the alloy are significantly reduced (Table 2). After heat treatment, alloys in Comparative Examples 2 and 3 exhibit a mixed-grain structure with both coarse and fine grains. Figure 10 This makes it difficult for grains to coordinate deformation during creep, which easily promotes the premature formation of creep pores and microcracks, thus reducing its high-temperature creep life (Table 3). Comparative Example 2 alloy contains M6C carbides aggregated along the hot working direction. Figure 10 These areas are more likely to become nucleation sites for pores and microcracks, thus significantly reducing the alloy's plasticity and creep life (Tables 3 and 4). In summary, improper preparation and heat treatment methods will not guarantee that high-tungsten, high-molybdenum nickel-based alloy plates possess both excellent high-temperature strength and plasticity.

[0139] The microstructure characterization and mechanical property test results of the alloys in Examples 1-3 above show that the method for preparing and heat-treating high-tungsten, high-molybdenum nickel-based high-temperature alloy plates provided by the present invention can ensure that the alloy obtains a uniformly distributed carbide and grain structure. The secondary M6C carbides are spherical or blocky, dispersed in the grains, with an average size ≤3μm. The grain shape is equiaxed, with uniform grain size and an average grain size ≤200μm, so that the alloy has both excellent strength and plasticity.

[0140] It will be readily understood by those skilled in the art that, without conflict, the advantageous technical features of the above-mentioned methods can be freely combined and superimposed.

[0141] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention. The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the protection scope of the present invention.

Claims

1. A method for preparing a nickel-based superalloy, characterized in that, Includes the following steps: Step 1): Electroslag remelting is performed on the nickel-based superalloy ingot to obtain an electroslag ingot; In this process, after the electroslag remelting treatment, primary M6C carbide and primary SiC carbide are precipitated in the electroslag ingot. Step 2): The electroslag ingot is homogenized to dissolve the primary M6C carbide and the primary SiC carbide, thereby obtaining a homogenized electroslag ingot. Step 3): The electroslag ingot after homogenization is forged to precipitate and disperse secondary M6C carbides in the matrix, thereby obtaining the nickel-based high-temperature alloy.

2. The method for preparing the nickel-based superalloy according to claim 1, characterized in that, The slag used in the electroslag remelting process includes: 70-85 wt.% CaF2, 10-20 wt.% CaO, and 5-15 wt.% Al2O3; and / or During the electroslag remelting process, argon gas is introduced for protection; preferably, the flow rate of argon gas is 10~20 L / min.

3. The method for preparing the nickel-based superalloy according to claim 1, characterized in that, After the forging process, the process further includes: heat treating the forged nickel-based superalloy. Preferably, the heat treatment temperature is 1180~1220℃; the heat treatment holding time is 30~120min.

4. The method for preparing the nickel-based superalloy according to claim 1, characterized in that, The homogenization treatment temperature is 1200~1250℃; preferably, the electroslag ingot is heated to 1000℃ at a rate of 10~20℃ / min by furnace heating, and then heated to 1200~1250℃ at a rate of 3~8℃ / min; and / or The homogenization treatment time T = T0 + K·(D-100), where T0 is the holding time of the homogenization treatment when the diameter D of the electroslag ingot is ≤100mm, which is 30~40h; K is the increment of the holding time corresponding to each 1mm increase in the diameter of the electroslag ingot, which is 0.03~0.04h / mm.

5. The method for preparing the nickel-based superalloy according to claim 1, characterized in that, After the homogenization treatment, the dissolution rate of primary M6C carbide is ≥90%, and the dissolution rate of primary SiC carbide is ≥90%.

6. The method for preparing the nickel-based superalloy according to claim 1, characterized in that, The forging process involves ≥3 forging passes; the initial forging temperature for each pass is 1175~1250℃, and the final forging temperature is ≥950℃; the total deformation of the forging process is ≥30%.

7. The method for preparing the nickel-based superalloy according to claim 1, characterized in that, By mass percentage, the nickel-based superalloy ingot contains ≥60wt% Ni, ≥9wt% W, ≥4.8wt% Mo, ≥20wt% Cr, ≥0.05wt% C, ≥0.3wt% Si, ≥0.3wt% Mn, ≥0.001wt% B, ≤0.001% O, and ≤0.001% S.

8. The method for preparing the nickel-based superalloy according to claim 1, characterized in that, The nickel-based superalloy ingot is obtained by vacuum induction melting of the raw materials; Preferably, the vacuum induction melting process specifically includes: placing the raw material in a vacuum induction melting furnace, melting the raw material when the vacuum degree is ≤1.0Pa, and refining it at a high temperature of 1500~1600℃; wherein, the high temperature refining time is T=T0+C·(W−100); wherein, T0 is the refining time when the raw material weight W≤100kg, which is 15~40min; C is the refining time increment corresponding to each 1kg increase in raw material weight, which is 0.04~0.05 min / kg; T≤240min.

9. The method for preparing the nickel-based superalloy according to claim 3, characterized in that, Before the heat treatment step, the process further includes: rolling the forged nickel-based superalloy. Preferably, the initial temperature of the rolling process is 1170~1230℃, the final rolling temperature is ≥950℃, and the total deformation of the rolling process is ≥50%.

10. A nickel-based superalloy, characterized in that, The nickel-based superalloy is obtained by the preparation method according to any one of claims 1 to 8; the M6C carbide in the nickel-based superalloy is spherical or blocky and dispersed in the grains, and the average size of the M6C carbide is ≤3μm; the grains are equiaxed and the average size of the grains is ≤200μm. The nickel-based superalloy has a yield strength Rp0.2≥220MPa, a tensile strength Rm≥470MPa, and an elongation A≥45% at 750℃; the nickel-based superalloy has a creep life ≥80h at 750℃ and 200MPa, and an elongation A≥45%.

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