A special Ni-Cr-Nb-Mo quaternary intermediate alloy for high-temperature alloy and a preparation method thereof

Abstract

The application relates to a special Ni-Cr-Nb-Mo quaternary intermediate alloy for high-temperature alloy and a preparation method thereof. The Ni-Cr-Nb-Mo quaternary intermediate alloy is prepared from raw materials containing the following weight percentages: Cr, 20.00-31.00%; Nb, 3.00-7.00%; Mo, 10.00-16.00%; and Ni and inevitable impurities, the balance; and the preparation method comprises the following steps: preparing raw materials containing Ni, Cr, Nb and Mo according to the proportion; adding a Ni / Cr / Nb metal mixture and Mo powder into a vacuum induction melting furnace, heating to melt, and performing refining and electromagnetic stirring under the protection of argon; and after the refining is completed, post-treatment is performed to obtain the Ni-Cr-Nb-Mo quaternary intermediate alloy. The Ni-Cr-Nb-Mo quaternary intermediate alloy can effectively reduce the comprehensive melting point, improve the element dissolution efficiency and uniformity, and improve the metallurgical quality of the high-temperature alloy.

Description

Technical Field

[0001] This invention relates to the technical field of alloy processing, and in particular to a Ni-Cr-Nb-Mo quaternary master alloy for high-temperature alloys and its preparation method. Background Technology

[0002] Inconel 625, a typical nickel-based austenitic wrought superalloy, possesses excellent high-temperature mechanical properties, structural stability, and hot and cold working performance, making it widely used in key fields such as aerospace, chemical engineering, petroleum, marine engineering, and nuclear energy. The microstructure and properties of Inconel 625 are fundamentally dependent on its chemical composition. During the vacuum induction melting process of superalloys, the melting points of the added alloying elements vary considerably: electrolytic nickel has a melting point of 1453℃, metallic chromium 1856℃, metallic niobium 2468℃, and metallic molybdenum 2623℃. If high-melting-point elements (especially niobium and molybdenum) are added directly in pure metallic form, the melting temperature needs to be increased, which can lead to the volatilization loss of low-melting-point elements and deviations in alloy composition. Therefore, in the practice of superalloy melting, high-melting-point alloying elements are usually pre-melted into an intermediate alloy (master alloy) before being added to the target alloy. The inherited characteristics of the intermediate alloy allow it to transfer compositional and microstructural properties to the casting. However, most existing intermediate alloys are designed for single alloying elements (such as Ni-Nb) or simple binary systems, and cannot provide the precise proportions of multiple high-melting-point raw materials such as Cr, Mo, and Nb required for the target high-temperature alloy. In practice, other high-melting-point metals still need to be added, resulting in a melting temperature that is significantly higher than expected. This causes the low-melting-point metals to vaporize and volatilize, making it difficult to guarantee the accuracy of the composition. Furthermore, problems such as slow melting speed, severe segregation, high energy consumption, and low purity also exist. Summary of the Invention

[0003] In view of the shortcomings of the existing technology, the first objective of this invention is to provide a Ni-Cr-Nb-Mo quaternary master alloy for high-temperature alloys, which can effectively reduce the overall melting point, improve the melting efficiency and uniformity of elements, and improve the metallurgical quality of high-temperature alloys.

[0004] The second objective of this invention is to provide a method for preparing a Ni-Cr-Nb-Mo quaternary master alloy for high-temperature alloys, which has the advantages of stable process, low impurity content and precise composition control.

[0005] To achieve the first objective mentioned above, the present invention provides the following technical solution: A high-temperature alloy-specific Ni-Cr-Nb-Mo quaternary master alloy is made from raw materials containing the following weight percentages: Cr: 20.00~31.00%, Nb: 3.00~7.00%, Mo: 10.00~16.00%, Ni and unavoidable impurities: balance.

[0006] By adopting the above technical solution, the present invention pre-alloys high-melting-point elements such as Cr, Nb, and Mo with Ni to form a low-melting-point quaternary master alloy. Compared with pure metals Nb (melting point 2468℃) and Mo (melting point 2623℃), the complete melting temperature of the master alloy of the present invention can be reduced to about 1300℃, which significantly reduces the melting temperature during subsequent vacuum induction melting, avoids the volatilization loss of low-melting-point elements (such as Ni), and improves the accuracy of composition control and melting efficiency.

[0007] Furthermore, the Ni-Cr-Nb-Mo quaternary master alloy is made from raw materials comprising the following weight percentages: Cr: 23.00~25.00%, Nb: 3.00~5.00%, Mo: 11.00~13.00%, Ni and unavoidable impurities: balance.

[0008] Furthermore, the Ni-Cr-Nb-Mo quaternary master alloy is made from raw materials comprising the following weight percentages: Cr: 24.12%, Nb: 3.94%, Mo: 12.02%, Ni and unavoidable impurities: balance.

[0009] By adopting the above-mentioned optimized proportions, the compositional requirements of Inconel 625 high-temperature alloy for Cr, Mo, and Nb can be fully met without the need to add pure metals. Furthermore, the alloy has a stable FCC_L12 phase as its matrix at high temperatures, exhibiting good plasticity, structural stability, and elemental solid solution capability.

[0010] Furthermore, the Ni-Cr-Nb-Mo quaternary master alloy is used to optimize the smelting process of Inconel 625 superalloy, which is made from raw materials containing the following weight percentages: C: ≤0.10%, Cr: 20.00~23.00%, Mo: 8.00~10.00%, Al: ≤0.40%, Ti: ≤0.40%, Nb: 3.15~4.15%, Fe: ≤5.00%, Ni and unavoidable impurities: balance.

[0011] To achieve the second objective mentioned above, the present invention provides the following technical solution: A method for preparing a Ni-Cr-Nb-Mo quaternary master alloy for high-temperature alloys includes the following steps: S1 prepares raw materials containing Ni, Cr, Nb, and Mo according to the specified ratio; wherein, Ni, Cr, and Nb are Ni / Cr / Nb metal mixtures obtained simultaneously through an aluminothermic reduction reaction; S2 adds the Ni / Cr / Nb metal mixture and Mo powder obtained in S1 into a vacuum induction melting furnace, heats it until it melts, and then refines and electromagnetically stirs it under argon protection. After refining, it undergoes post-processing to obtain a Ni-Cr-Nb-Mo quaternary master alloy.

[0012] By adopting the above technical solution, a Ni / Cr / Nb metal mixture is first prepared simultaneously through aluminothermic reduction, and then vacuum induction melting is carried out with Mo powder. This effectively avoids the difficulty of melting each high-melting-point metal separately. At the same time, the vacuum environment and argon protection reduce the content of impurities such as oxygen, sulfur, and phosphorus, and improve the purity of the intermediate alloy. Electromagnetic stirring promotes the homogenization of the molten pool and improves the element yield and composition control accuracy.

[0013] Furthermore, in S1, the aluminothermic reaction uses Al particles as a reducing agent and NaClO3 as an auxiliary exothermic agent to reduce the reaction raw materials containing NiO, Cr2O3 and Nb2O5 to elemental Ni, Cr and Nb metals. The reaction vessel is a magnesium crucible.

[0014] Furthermore, in S1, the particle size of Al particles is controlled to be <0.5 mm and the amount added is ≤98% of the theoretical amount.

[0015] Furthermore, in S1, the purity of NiO, Cr2O3 and Nb2O5 in the reaction raw materials is controlled to be ≥99%, the S content is ≤0.02%, and the contents of Pb, As, Sn and Sb are ≤0.001% respectively.

[0016] Furthermore, in S1, Al particles, NaClO3, and reaction raw materials containing NiO, Cr2O3, and Nb2O5 are first mixed in a reaction vessel for ≥2 hours, then dried at 240~280℃ for 1.5~2.5 hours, and then heated to 450~550℃. The vacuum degree inside the reaction vessel is reduced to below 5 Pa, and the aluminothermic reaction is initiated by ignition.

[0017] Furthermore, in S1, before mixing, NaClO3 is passed through a 60-mesh sieve, and Al particles and reaction raw materials are passed through a 200-mesh sieve respectively.

[0018] Furthermore, in S1, before ignition, the vacuum is first reduced to below 3 Pa, high-purity argon is introduced to 30000 Pa for gas purging, and then the vacuum is reduced to 3 Pa again before ignition.

[0019] Furthermore, in S1, the purity of the Mo powder is controlled to be ≥99.5%.

[0020] Furthermore, in S2, the vacuum induction melting process is heated to above 1600°C to melt. During the melting process, 30000Pa high-purity argon gas is introduced for protection. After complete melting, the temperature is lowered to 1400~1600°C for refining for 10~20 minutes. During the refining process, the molten pool is electromagnetically stirred. The stirring method is to stir for 1~2 minutes, stop for 1~2 minutes, and repeat at least 3 times.

[0021] Furthermore, in S2, after refining, the raw materials are melted and refined for 25-35 minutes, then cooled to 1400-1500℃ for casting, and then cooled in the furnace for 18-22 hours before being removed from the furnace.

[0022] In summary, the beneficial technical effects of the present invention are as follows: 1. This invention pre-alloys high-melting-point elements such as Cr, Nb, and Mo, effectively reducing the overall liquidus temperature of the material, improving the melting efficiency of high-melting-point elements and the molten pool response rate, reducing the melting lag and settling phenomenon of Nb and Mo, significantly improving the uniformity of element distribution, and reducing dendrite segregation and the tendency of Laves phase formation. 2. This invention utilizes high-purity raw materials and employs argon gas furnace cleaning protection measures in a vacuum environment to effectively reduce the content of impurities such as oxygen, sulfur, and phosphorus, thereby reducing the generation of oxide inclusions, unmelted particles, and secondary pollution, and improving the purity of the intermediate alloy and the final 625 high-temperature alloy. 3. The present invention, in conjunction with periodic electromagnetic stirring during the smelting process, further promotes the homogenization of the molten pool, improves the yield of Cr, Nb and Mo elements and the accuracy of composition control, and reduces the number of subsequent composition adjustments. 4. The intermediate alloy of the present invention melts faster, which can shorten the time of vacuum induction melting, reduce energy consumption, reduce the damage to crucibles and equipment caused by high temperature splashing and local overheating, and improve the stability of production and the applicability of industrial continuous melting. Experiments show that compared with pure metal smelting, the smelting time is shortened by 45% and energy consumption is reduced by 30%. Attached Figure Description

[0023] Figure 1 This is a graph showing the physical properties of the Ni-Cr-Nb-Mo quaternary master alloy prepared in Example 1 of this invention.

[0024] Figure 2 This is a graph showing the physical properties of the Ni-Cr-Nb-Mo quaternary master alloy prepared in Example 2 of this invention.

[0025] Figure 3 This is a graph showing the physical properties of the Ni-Cr-Nb-Mo quaternary master alloy prepared in Example 3 of this invention.

[0026] Figure 4 This is a graph showing the physical properties of the Ni-Cr-Nb-Mo quaternary master alloy prepared in Comparative Example 1 of this invention.

[0027] Figure 5 This is a phase content detection diagram of the Ni-Cr-Nb-Mo quaternary master alloy prepared in Example 1 of the present invention.

[0028] Figure 6 This is a phase content detection diagram of the Ni-Cr-Nb-Mo quaternary master alloy prepared in Comparative Example 1 of this invention.

[0029] Figure 7 This is an energy consumption diagram of the alloy smelting of Inconel 625 high-temperature alloy in Embodiment 1 of the present invention.

[0030] Figure 8 This is an energy consumption diagram of the alloy smelting of Inconel 625 high-temperature alloy in Comparative Example 2 of this invention.

[0031] Figure 9 This is a graph showing the physical properties of the alloy in Comparative Example 3 of this invention. Detailed Implementation

[0032] To make the technical means, creative features, objectives and effects of this invention clearer and easier to understand, the invention will be further described below in conjunction with the accompanying drawings and specific embodiments. Example

[0033] Example 1: A high-temperature alloy-specific Ni-Cr-Nb-Mo quaternary master alloy disclosed in this invention is made from raw materials containing the following weight percentages: Cr: 24.12%, Nb: 3.94%, Mo: 12.02%, Ni and unavoidable impurities: balance.

[0034] This invention also discloses a method for preparing a Ni-Cr-Nb-Mo quaternary master alloy for high-temperature alloys, which includes the following steps: S1 prepares raw materials containing Ni, Cr, Nb, and Mo according to the specified proportions; among which, The purity of Mo powder should be controlled to ≥99.5%; Ni, Cr, and Nb are a Ni / Cr / Nb metal mixture simultaneously prepared via an aluminothermic reduction reaction. The aluminothermic reaction uses Al particles as a reducing agent and NaClO3 as an auxiliary exothermic agent to reduce the reaction raw materials containing NiO, Cr2O3, and Nb2O5 to elemental Ni, Cr, and Nb. The reaction vessel is a magnesium crucible. The specific implementation method is as follows... S11 pre-processes NaClO3 through a 60-mesh sieve, and Al particles and reaction raw materials through a 200-mesh sieve respectively; wherein, the particle size of Al particles is controlled to be <0.5mm and the amount added is ≤98% of the theoretical amount; and the purity of NiO, Cr2O3 and Nb2O5 in the reaction raw materials is controlled to be ≥99%, the S content is ≤0.02%, and the contents of Pb, As, Sn and Sb are ≤0.001% respectively; S12 first mixes Al particles, NaClO3, and reaction raw materials containing NiO, Cr2O3 and Nb2O5 in a reaction vessel for 2 hours, then bakes at 260°C for 2.0 hours, then heats to 500°C, evacuates the vacuum in the reaction vessel to 3Pa, and purges it with high-purity argon to 30000Pa for gas washing. After evacuating the vacuum to 3Pa again, it is ignited to initiate the aluminothermic reaction. S2 involves adding the Ni / Cr / Nb metal mixture obtained in S1 and Mo powder into a vacuum induction melting furnace, heating until a clear melt is formed, and then refining and electromagnetically stirring under argon protection. After refining, post-processing yields a Ni-Cr-Nb-Mo quaternary master alloy. S21 adds the Ni / Cr / Nb metal mixture obtained in S1 and Mo powder into a vacuum induction melting furnace and heats it to 1600℃ to melt. During the melting process, 30000Pa high-purity argon gas is introduced for protection to prevent material splashing. After S22 is completely melted, it is cooled to 1500℃ and refined for 15 minutes. During the refining process, the molten pool is electromagnetically stirred. The stirring method is to stir for 1 minute and stop for 1 minute, and repeat at least 3 times to ensure the mixing of the elemental raw materials. After S23 refining is completed, the raw materials are melted and refined for 30 minutes. After refining, the temperature is lowered to 1450℃ for casting. After casting, the material is cooled in the furnace for 20 hours before being taken out of the furnace.

[0035] Example 2: This is a Ni-Cr-Nb-Mo quaternary master alloy for high-temperature alloys disclosed in this invention. The difference from Example 1 is that the weight percentage of each component in the raw materials is shown in Table 1.

[0036] Example 3: This is a Ni-Cr-Nb-Mo quaternary master alloy for high-temperature alloys disclosed in this invention. The difference from Example 1 is that the weight percentage of each component in the raw materials is shown in Table 1.

[0037] Example 4: This invention discloses a method for preparing a Ni-Cr-Nb-Mo quaternary master alloy for high-temperature alloys. The difference from Example 1 is that it includes the following steps: S1 prepares raw materials containing Ni, Cr, Nb, and Mo according to the specified proportions; among which, The purity of Mo powder should be controlled to ≥99.5%; Ni, Cr, and Nb are a Ni / Cr / Nb metal mixture simultaneously prepared via an aluminothermic reduction reaction. The aluminothermic reaction uses Al particles as a reducing agent and NaClO3 as an auxiliary exothermic agent to reduce the reaction raw materials containing NiO, Cr2O3, and Nb2O5 to elemental Ni, Cr, and Nb. The reaction vessel is a magnesium crucible. The specific implementation method is as follows... S11 pre-processes NaClO3 through a 60-mesh sieve, and Al particles and reaction raw materials through a 200-mesh sieve respectively; wherein, the particle size of Al particles is controlled to be <0.5mm and the amount added is ≤98% of the theoretical amount; and the purity of NiO, Cr2O3 and Nb2O5 in the reaction raw materials is controlled to be ≥99%, the S content is ≤0.02%, and the contents of Pb, As, Sn and Sb are ≤0.001% respectively; S12 first mixes Al particles, NaClO3, and reaction raw materials containing NiO, Cr2O3 and Nb2O5 in a reaction vessel for 2 hours, then bakes at 240°C for 1.5 hours, then heats to 450°C, evacuates the reaction vessel to 3Pa, and purges it with high-purity argon gas to 30000Pa for gas washing. After evacuating to 3Pa again, it is ignited to initiate the aluminothermic reaction. S2 involves adding the Ni / Cr / Nb metal mixture obtained in S1 and Mo powder into a vacuum induction melting furnace, heating until a clear melt is formed, and then refining and electromagnetically stirring under argon protection. After refining, post-processing yields a Ni-Cr-Nb-Mo quaternary master alloy. S21 adds the Ni / Cr / Nb metal mixture obtained in S1 and Mo powder into a vacuum induction melting furnace and heats it to 1600℃ to melt. During the melting process, 30000Pa high-purity argon gas is introduced for protection to prevent material splashing. After S22 is completely melted, it is cooled to 1400℃ and refined for 10 minutes. During the refining process, the molten pool is electromagnetically stirred. The stirring method is to stir for 1 minute and stop for 1 minute, and repeat 3 times to ensure the mixing of the elemental raw materials. After S23 refining is completed, the raw materials are melted and refined for 25 minutes. After refining, the temperature is lowered to 1400℃ for casting. After casting, the material is cooled in the furnace for 18 hours before being removed from the furnace.

[0038] Example 5: This invention discloses a method for preparing a Ni-Cr-Nb-Mo quaternary master alloy for high-temperature alloys. The difference from Example 1 is that it includes the following steps: S1 prepares raw materials containing Ni, Cr, Nb, and Mo according to the specified proportions; among which, The purity of Mo powder should be controlled to ≥99.5%; Ni, Cr, and Nb are a Ni / Cr / Nb metal mixture simultaneously prepared via an aluminothermic reduction reaction. The aluminothermic reaction uses Al particles as a reducing agent and NaClO3 as an auxiliary exothermic agent to reduce the reaction raw materials containing NiO, Cr2O3, and Nb2O5 to elemental Ni, Cr, and Nb. The reaction vessel is a magnesium crucible. The specific implementation method is as follows... S11 pre-processes NaClO3 through a 60-mesh sieve, and Al particles and reaction raw materials through a 200-mesh sieve respectively; wherein, the particle size of Al particles is controlled to be <0.5mm and the amount added is ≤98% of the theoretical amount; and the purity of NiO, Cr2O3 and Nb2O5 in the reaction raw materials is controlled to be ≥99%, the S content is ≤0.02%, and the contents of Pb, As, Sn and Sb are ≤0.001% respectively; S12 first mixes Al particles, NaClO3, and reaction raw materials containing NiO, Cr2O3 and Nb2O5 in a reaction vessel for 3 hours, then bakes at 280°C for 2.5 hours, then heats to 550°C, evacuates the reaction vessel to 3 Pa, and purges it with high-purity argon gas to 30000 Pa for gas washing. After evacuating the vessel to 3 Pa again, it is ignited to initiate the aluminothermic reaction. S2 involves adding the Ni / Cr / Nb metal mixture obtained in S1 and Mo powder into a vacuum induction melting furnace, heating until a clear melt is formed, and then refining and electromagnetically stirring under argon protection. After refining, post-processing yields a Ni-Cr-Nb-Mo quaternary master alloy. S21 adds the Ni / Cr / Nb metal mixture obtained in S1 and Mo powder into a vacuum induction melting furnace and heats it to 1600℃ to melt. During the melting process, 30000Pa high-purity argon gas is introduced for protection to prevent material splashing. After S22 is completely melted, it is cooled to 1600℃ and refined for 20 minutes. During the refining process, the molten pool is electromagnetically stirred. The stirring method is to stir for 2 minutes, stop for 2 minutes, and repeat 3 times to ensure the mixing of elemental raw materials. After S23 refining is completed, the raw materials are melted and refined for 35 minutes. After refining, the temperature is lowered to 1500℃ for casting. After casting, the material is cooled in the furnace for 22 hours before being removed from the furnace. Comparative Example

[0039] Comparative Example 1: This is a Ni-Cr-Nb-Mo quaternary master alloy for high-temperature alloys disclosed in this invention. The difference from Example 1 is that the weight percentage of each component in the raw materials is shown in Table 1.

[0040] Comparative Example 2: This is a Ni-Cr-Nb-Mo quaternary master alloy for high-temperature alloys disclosed in this invention. The difference from Example 1 is that equal amounts of Ni, Cr, Nb, and Mo metal powders are used instead of the Ni-Cr-Nb-Mo quaternary master alloy.

[0041] Comparative Example 3: This is a Ni-Cr-Nb-Mo quaternary master alloy for high-temperature alloys disclosed in this invention. The difference from Example 1 is that an Nb-Cr binary alloy is used instead of the Ni-Cr-Nb-Mo quaternary master alloy.

[0042] Comparative Example 4: This is a Ni-Cr-Nb-Mo quaternary master alloy for high-temperature alloys disclosed in this invention. The difference from Example 1 is that a Ni-Cr-Nb ternary alloy is used instead of the Ni-Cr-Nb-Mo quaternary master alloy.

[0043] Table 1 Example 1 24.12 3.94 12.02 margin Example 2 30.24 6.05 15.16 margin Example 3 25.97 4.99 14.03 margin Comparative Example 1 21.95 3.04 9.94 margin Performance testing

[0044] Experimental Example 1: The Ni-Cr-Nb-Mo quaternary master alloys prepared in Examples 1-3 and Comparative Example 1 were tested for physical properties such as solid fraction, thermal conductivity, liquid viscosity, and specific heat capacity. The test results are as follows: Figures 1-4 As shown.

[0045] from Figure 1 It can be seen that the complete melting temperature of the Ni-Cr-Nb-Mo quaternary alloy in Example 1 is approximately 1328℃, with the melting point showing an upward trend, but this temperature is already within the normal operating temperature for vacuum induction melting. The thermal conductivity is slightly lower in the low-temperature range than in Examples 1 and 2, but close in the high-temperature range. Overall, it is at a moderate level, ensuring heat transfer during the melting process. The viscosity decreases slightly with increasing temperature, especially below 17 mPa·s above 1200℃ and only 9.0 mPa·s at 1400℃, exhibiting excellent fluidity. It has the lowest high-temperature viscosity among all examples, making it easy to cast and fill molds, significantly reducing porosity and shrinkage in the ingot, and improving ingot density. It also facilitates rapid homogenization of the composition during melting. The specific heat capacity is similar to that of Example 1, but has limited impact on the intermediate alloy ingot itself. Furthermore, this formulation fully meets the Cr, Mo, and Nb composition requirements of Inconel 625 high-temperature alloy, without the need for additional pure metals. Therefore, this formulation is the optimal one.

[0046] from Figure 2 It can be seen that the complete melting temperature of the Ni-Cr-Nb-Mo quaternary alloy in Example 2 is approximately 1263℃, significantly lower than the melting points of Nb (2477℃) and Mo (2623℃). This indicates that Ni-based pre-alloying can effectively reduce the overall melting difficulty of high-melting-point elements, avoiding problems such as melting lag, settling, and local segregation that occur with pure Nb and pure Mo during vacuum induction melting, thus making it more suitable for vacuum induction melting processes.

[0047] The thermal conductivity increased from 27 W / (m·K) at 1150℃ to 25 W / (m·K) at 1400℃, which is above average. This facilitates rapid heat transfer into the alloy during melting, shortening the melting cycle and improving production efficiency. It also reduces localized overheating and results in more uniform composition. The low viscosity, especially at only 10.0 mPa·s at 1400℃, indicates good fluidity of the alloy liquid, facilitating casting and aiding in ingot filling and shrinkage compensation, reducing casting defects such as shrinkage cavities and porosity. The specific heat capacity is higher than other schemes, resulting in the best temperature stability. However, this also indicates a longer melting time is required. Furthermore, approximately 18.9% pure metallic Cr by weight of the Inconel 625 high-temperature alloy still needs to be added, thus presenting certain limitations in smelting.

[0048] from Figure 3 It can be seen that the complete melting temperature of the Ni-Cr-Nb-Mo quaternary alloy in Example 3 is approximately 1295℃, which is slightly higher than that of Example 1. Its thermal conductivity is similar to that of Example 1, sufficient to ensure effective heat transfer during melting and avoid localized overheating. The overall viscosity is slightly higher than that of Example 1, with a higher viscosity in the low-temperature range (1150℃). If the casting temperature is too low, it may affect the filling capacity. The specific heat capacity of this alloy is higher in the low-temperature range than that of Example 1, and lower in the high-temperature range, which is beneficial to the thermal stability of the molten pool and reduces temperature fluctuations. However, this composition still requires the addition of a large amount of Cr metal, and the Mo-Nb ratio is not ideal.

[0049] from Figure 4 It can be seen that the complete melting temperature of the Ni-Cr-Nb-Mo quaternary alloy in Comparative Example 1 is approximately 1390℃, with the melting point showing an upward trend, still within the normal operating temperature range for vacuum induction melting. Its thermal conductivity is significantly higher than that of the example, its viscosity is lower, and its specific heat capacity is lower, indicating poor temperature stability. Furthermore, the Nb content is insufficient, necessitating the addition of niobium (approximately 0.15~1.15%), negating the purpose of the intermediate alloy completely replacing the high-melting-point element.

[0050] Experimental Example 2: The phase content of the Ni-Cr-Nb-Mo quaternary master alloys prepared in Examples 1 and 3 was determined, and the test results are as follows: Figures 5-6 As shown.

[0051] from Figure 5It can be seen that the Ni-Cr-Nb-Mo quaternary alloy of Example 1 mainly uses the FCC_L12 phase as the matrix in the temperature range of 500~1300℃, and the phase content remains at a high level, indicating that the system has good nickel-based solid solution stability. The FCC_L12 phase belongs to a typical Ni-based face-centered cubic structure, possessing good plasticity, structural stability, and elemental solid solution capability, which can effectively improve the structural uniformity and thermal stability of the intermediate alloy during the melting process. With increasing temperature, the FCC_L12 phase gradually increases, and almost completely occupies the system above approximately 1000℃, indicating that the alloy can form a stable single matrix structure under high-temperature conditions. This is of great significance for uniform element diffusion and melt pool stability during vacuum induction melting. Although the alloy contains certain intermetallic compounds and brittle phases at low temperatures, these precipitated phases can be effectively dissolved under actual vacuum induction melting temperatures and will not remain stable for a long time during melting. Therefore, they will not significantly increase melt brittleness or cause serious segregation problems.

[0052] from Figure 6 It can be seen that the Ni-Cr-Nb-Mo quaternary alloy of Example 2 contains multiple intermediate phases, among which the harmful P phase and σ phase are abundant and present in high amounts (40%~44%) over a wide temperature range, with a large amount of σ phase present in the 600-1200℃ range. If these harmful phases are retained during the solidification of the intermediate alloy, their plasticity and toughness will be severely deteriorated, and cracks may occur during subsequent transportation or remelting; at the same time, these phases may be inherited by the target high-temperature alloy, reducing the mechanical properties of the Inconel 625 high-temperature alloy. A small amount of ordered body-centered cubic (BCC) intermetallic compound structures are also present. These belong to solid solution phases with specific segregation or ordering, which will also have an adverse effect on the material properties.

[0053] Experimental Example 3: The alloys of Examples 1 and Comparative Examples 2-4 were used to optimize the smelting process of Inconel 625 superalloy. Inconel 625 superalloy is made from raw materials containing the following weight percentages: C: ≤0.10%, Cr: 20.00~23.00%, Mo: 8.00~10.00%, Al: ≤0.40%, Ti: ≤0.40%, Nb: 3.15~4.15%, Fe: ≤5.00%, Ni and unavoidable impurities: balance.

[0054] Inconel 625 superalloy was smelted using the Ni-Cr-Nb-Mo quaternary alloy from Example 1. The total weight of the Inconel 625 superalloy product was 25 kg. The vacuum degree was ≤20 Pa, refining time was 30 minutes, refining temperature was 1430~1480℃, and casting temperature was 1400℃. The smelting process is as follows: Figure 7As shown: the entire process takes only 0.8 hours (about 50 minutes), and the rated energy consumption is 25KW. Compared with pure metal smelting, the smelting process is shortened by 45% and energy consumption is reduced by 30%.

[0055] Comparative Example 2 uses equal amounts of Ni, Cr, Nb, and Mo metal powders instead of the Ni-Cr-Nb-Mo quaternary master alloy. The smelting requirements are the same as in Example 1, and the materials are added in the order of Ni, Fe → Nb, Mo, Cr → Al, Ti. The smelting process is as follows: Figure 8 As shown: The smelting time lasted for nearly 1.5 hours, with a total energy consumption of about 35KW. The energy consumption growth rate was particularly obvious during the material melting period.

[0056] Comparative Example 3 prepared a Nb / Cr binary alloy separately based on the preparation method of Example 1. Figure 9 It can be seen that its lowest melting point is 1621℃, but this ratio cannot meet the composition requirements of Inconel 625 high-temperature alloy. Therefore, if this simple binary alloy is used, its melting point is better than 1621℃. At the same time, high-melting-point metals such as Mo need to be added. Inconel 625 high-temperature alloy still needs to be heated to above 2400℃ during the smelting process, which reduces the material yield. Similarly, the same problem exists when using the ternary alloy (Ni-Cr-Nb) of Comparative Example 4.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A Ni-Cr-Nb-Mo quaternary master alloy for high-temperature alloys, characterized in that: Made from raw materials containing the following weight percentages: Cr: 20.00~31.00%, Nb: 3.00~7.00%, Mo: 10.00~16.00%, Ni and unavoidable impurities: balance.

2. The Ni-Cr-Nb-Mo quaternary master alloy for high-temperature alloys according to claim 1, characterized in that: Made from raw materials containing the following weight percentages: Cr: 24.12%, Nb: 3.94%, Mo: 12.02%, Ni and unavoidable impurities: balance.

3. The method for preparing a Ni-Cr-Nb-Mo quaternary master alloy for high-temperature alloys according to any one of claims 1 to 2, characterized in that: Includes the following steps, S1 prepares raw materials containing Ni, Cr, Nb, and Mo according to the specified ratio; wherein, Ni, Cr, and Nb are Ni / Cr / Nb metal mixtures obtained simultaneously through an aluminothermic reduction reaction; S2 adds the Ni / Cr / Nb metal mixture and Mo powder obtained in S1 into a vacuum induction melting furnace, heats it until it melts, and then refines and electromagnetically stirs it under argon protection. After refining, it undergoes post-processing to obtain a Ni-Cr-Nb-Mo quaternary master alloy.

4. The method for preparing a Ni-Cr-Nb-Mo quaternary master alloy for high-temperature alloys according to claim 3, characterized in that: In S1, the aluminothermic reaction uses Al particles as a reducing agent and NaClO3 as an auxiliary exothermic agent to reduce the reaction raw materials containing NiO, Cr2O3 and Nb2O5 to elemental Ni, Cr and Nb. The reaction vessel is a magnesium crucible.

5. The method for preparing a Ni-Cr-Nb-Mo quaternary master alloy for high-temperature alloys according to claim 4, characterized in that: In S1, the particle size of Al particles is controlled to be <0.5 mm and the amount added is ≤98% of the theoretical amount; and the purity of NiO, Cr2O3 and Nb2O5 in the reaction raw materials is controlled to be ≥99%, the S content is ≤0.02%, and the contents of Pb, As, Sn and Sb are ≤0.001% respectively.

6. The method for preparing a Ni-Cr-Nb-Mo quaternary master alloy for high-temperature alloys according to claim 4, characterized in that: In step S1, Al particles, NaClO3, and reaction raw materials containing NiO, Cr2O3, and Nb2O5 are first mixed in a reaction vessel for ≥2 hours. Then, the mixture is dried at 240~280℃ for 1.5~2.5 hours, followed by heating to 450~550℃. The vacuum degree inside the reaction vessel is reduced to below 5 Pa, and the aluminothermic reaction is initiated by ignition.

7. The method for preparing a Ni-Cr-Nb-Mo quaternary master alloy for high-temperature alloys according to claim 6, characterized in that: In S1, before mixing, NaClO3 is passed through a 60-mesh sieve, and Al particles and reaction raw materials are passed through a 200-mesh sieve respectively.

8. The method for preparing a Ni-Cr-Nb-Mo quaternary master alloy for high-temperature alloys according to claim 6, characterized in that: In S1, before ignition, the vacuum is first reduced to below 3 Pa, high-purity argon gas is introduced to 30000 Pa for gas washing, and then the vacuum is reduced to 3 Pa again before ignition.

9. The method for preparing a Ni-Cr-Nb-Mo quaternary master alloy for high-temperature alloys according to claim 3, characterized in that: In S2, the vacuum induction melting process is heated to above 1600°C to melt. During the melting process, 30000Pa high-purity argon gas is introduced for protection. After complete melting, the temperature is reduced to 1400~1600°C for refining for 10~20 minutes. During the refining process, the molten pool is electromagnetically stirred. The stirring method is to stir for 1~2 minutes and stop for 1~2 minutes, and repeat at least 3 times.

10. The method for preparing a Ni-Cr-Nb-Mo quaternary master alloy for high-temperature alloys according to claim 9, characterized in that: In step S2, after refining, the raw materials are melted and refined for 25-35 minutes, then cooled to 1400-1500℃ for casting, and then cooled in the furnace for 18-22 hours before being removed from the furnace.

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