NbmocrtaTi refractory high-entropy alloy and smelting method thereof

Abstract

The application discloses a NbMoCrTaTi refractory high-entropy alloy and a smelting method thereof, and belongs to the technical field of metallurgy. The chemical composition and mass content of the NbMoCrTaTi refractory high-entropy alloy are as follows: Nb 18-22%, Mo 19.5-21.5%, Cr 10-12%, Ta 38-42%, Ti 8.5-10.5%, and inevitable impurities. The smelting method comprises the following steps: vacuum induction smelting, plasma induction smelting and vacuum consumable smelting. The smelting process is divided into three stages. The main task of the first stage is vacuum degassing, and N, O, H and other gases are effectively removed. In the second stage, the plasma energy is utilized to rapidly melt tantalum, and a preliminarily mixed alloy ingot is prepared. In the third stage, the vacuum consumable smelting is utilized to remove inclusions and gases, and the alloy is mixed again after remelting and solidification. The obtained FeCrCoNiAl high-entropy alloy ingot is good in uniformity, and the macrosegregation index of the five elements is good.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology and relates to a refractory high-entropy alloy NbMoCrTaTi and its smelting method. Background Technology

[0002] High-entropy alloys are metallic alloys with high mixing entropy, formed by mixing five or more metallic elements in equiatomic or near-equiatomic ratios. They possess good thermal stability, low stacking fault energy, and excellent radiation resistance and corrosion resistance, and are widely used in aerospace, nuclear power, chemical, and food industries. Among the many high-entropy alloys, refractory high-entropy alloys have a more stable microstructure and retain good mechanical properties, oxidation resistance, damp heat resistance, and corrosion resistance in high-temperature, humid, acidic, and alkaline environments. They hold promise as a replacement for traditional nickel-based superalloys and have broad application prospects.

[0003] Refractory high-entropy alloys are classified into three types according to their microstructure. The first type is single-phase alloys consisting of only a bcc phase or a B2 phase. The second type includes two-phase alloys such as bcc+Laves, bcc+M5Si3, fcc+Ll2, bcc+hcp, B2+bcc, and B2+Al3Zr5. The third type consists of multiphase alloys such as 3bcc, 2bcc+Laves, bcc+Laves+M5Si3, bcc+Laves+Ll2, bcc+B2+Al3Zr5, and B2+Laves+Al3Zr5. It can be seen that most high-entropy alloys have a bcc phase as their matrix structure. Therefore, in the design of composition systems, elements with a bcc structure, such as Nb, Mo, Ta, and W, are often used as the main elements.

[0004] However, since elements such as Nb, Mo, Ta, and W belong to the 4d and 5d regions respectively, their atomic sizes and valence electron configurations differ significantly, resulting in substantial differences in atomic diffusion and bonding abilities. This makes homogeneous preparation in liquid phase more difficult, and powder metallurgy is often used to suppress segregation. However, due to the high cost, long process flow, and low production efficiency of powder metallurgy, its large-scale application has been difficult, which severely restricts the rapid development of high-entropy alloys.

[0005] Metallurgists have conducted extensive research to address the challenges of large-scale production of high-entropy alloys.

[0006] Publication number CN115198158A discloses an oxidation-resistant refractory high-entropy alloy and its preparation method. This method involves rough melting in a vacuum electric arc furnace, followed by inverted casting, homogenization annealing, and densification treatment to obtain the oxidation-resistant refractory high-entropy alloy. The method is very novel, but it places extremely high demands on the equipment; for example, the homogenization annealing requires a vacuum degree of 5 × 10⁻⁶. -3The pressure is below Pa, but current industrial vacuum pumps cannot achieve this, making it difficult to scale up and promote this method.

[0007] Publication number CN115213406A discloses a method for preparing refractory high-entropy alloys by explosive loading. The method uses vacuum ball milling, sealing, filling with explosives, and detonation to prepare refractory high-entropy alloys. The method is very advanced, but the residue after the detonation will inevitably affect the cleanliness of the high-entropy alloy. In addition, the detonation device and 8701 explosives are both controlled items, so this method is not advisable.

[0008] Publication number CN115109981A discloses an oxide dispersion-strengthened TaNbVTi refractory high-entropy alloy, its preparation method, and its applications. The method involves ball milling, spray granulation, and spheroidization to form spheres, followed by electron beam melting to obtain the refractory high-entropy alloy. The method is unique, but it has very strict requirements for raw materials. Powders such as Ta, Nb, V, and Ti require a particle size of 10–80 μm, while Y2O3 powder requires a particle size of 20–50 nm. These materials are difficult to supply in large quantities on the market, so they cannot be used on a large scale.

[0009] In addition, publication numbers CN115044870A, CN114855049A, and CN114855050A all disclose relatively novel and advanced methods for preparing refractory high-entropy alloys, but most of them have complex processes, high costs, and bleak prospects for large-scale production.

[0010] In summary, among the currently available technologies, there is no industrialized technology that can combine low cost, simple process, and stable quality. Summary of the Invention

[0011] To solve the above-mentioned technical problems, this invention provides a refractory high-entropy alloy NbMoCrTaTi and its smelting method. The technical solution adopted by this invention is as follows:

[0012] A refractory high-entropy alloy of NbMoCrTaTi has the following chemical composition and mass percentage: Nb 18-22%, Mo 19.5-21.5%, Cr 10-12%, Ta 38-42%, Ti 8.5-10.5%, with the balance being unavoidable impurity elements.

[0013] The smelting method for the above-mentioned NbMoCrTaTi refractory high-entropy alloy includes the following steps:

[0014] (1) Vacuum induction melting

[0015] A. 50±5% metallic chromium, all niobium bars and molybdenum bars are loaded into a pre-made zirconium oxide crucible in a vacuum induction furnace and melted under vacuum by applying electricity;

[0016] B. After the furnace charge has melted completely, add the remaining metallic chromium in batches. After all the charge has melted completely, raise the temperature and adjust it to a high vacuum for degassing until [O] ≤ 10 ppm, [N] ≤ 10 ppm, and [H] ≤ 1 ppm.

[0017] C. Stop the vacuum, fill with argon gas, adjust the temperature to 1520-1550℃, and pour the casting under power;

[0018] D. After the ingot cools to room temperature, it is demolded and cut into thin strips to obtain niobium-molybdenum-chromium alloy strips;

[0019] (2) Plasma induction melting

[0020] E. Load the niobium-molybdenum-chromium alloy strip, tantalum metal, and 3-5% of the total slag into the zirconium oxide prefabricated crucible of the plasma induction furnace, and rapidly melt them by passing through the plasma power supply and the induction power supply.

[0021] F. After the furnace charge is completely melted, stop the plasma power supply, keep the lance blowing argon, remove the slag, add the sponge titanium in batches, and after all the sponge titanium is completely melted, increase the induction power supply to fully stir the molten metal.

[0022] G. Adjust the temperature to 1450~1480℃, and cast the alloy ingot under electric current to be used as a consumable electrode;

[0023] (3) Vacuum consumable remelting

[0024] H. After annealing and polishing the consumable electrode, weld it onto the dummy electrode;

[0025] I. Perform vacuum arc remelting, maintaining a melting rate of 90–150 kg / h;

[0026] J. After melting, the ingot is demolded and placed in an argon-protected furnace for slow cooling.

[0027] Furthermore, in step A, the vacuum degree during melting is ≤0.67 Pa; in step B, the temperature is raised to the molten metal temperature of 1660~1700℃, and the vacuum degree during degassing is ≤0.06 Pa.

[0028] Further, in step C, the argon gas filling rate is 35000–70000 Pa, and the argon gas is dried and has a purity ≥99.99%; in step D, the ingot is cut into 30×30–50×50 mm pieces. 2 Thin strips of the specified size.

[0029] Furthermore, in step E, the plasma medium gas is argon gas with a purity of ≥99.99% and which has been dehydrated, and the flow rate is 120-200 L / min.

[0030] Furthermore, in step F, the amount of sponge titanium added each time is based on covering the surface of the molten metal; in step G, the length-to-diameter ratio of the casting mold is ≥6.

[0031] Furthermore, in step H, the annealing temperature of the consumable electrode is 1200–1250°C, and the time is 16–20 h.

[0032] Furthermore, in step I, during vacuum consumable remelting, the vacuum level is maintained at ≤0.1 Pa.

[0033] Furthermore, in step J, the surface temperature of the ingot is ≥650℃ during demolding, and the ingot is slowly cooled to ≤200℃ before being removed from the furnace.

[0034] The beneficial effects of adopting the above technical solution are as follows:

[0035] (1) The present invention divides the smelting process into three stages: vacuum induction smelting, plasma induction smelting, and vacuum self-consumption smelting. The main task of the first stage is vacuum degassing, which effectively removes gases such as N, O, and H from the alloy, especially chromium. The second stage utilizes the concentrated energy advantage of plasma to quickly melt tantalum metal, reducing the scouring of the crucible refractory material by electromagnetic stirring, and for the first time, a preliminarily homogenized alloy ingot is obtained. The third stage utilizes the advantage of vacuum self-consumption to remove inclusions and gases, and after remelting and solidification, the alloy is homogenized again.

[0036] (2) Using zirconia pre-made crucibles with better chemical stability during vacuum induction melting and plasma induction melting can greatly reduce the chemical reaction between the molten metal pool and the crucible, effectively reduce the oxygen supply to the crucible and the introduction of inclusions, and ensure the chemical composition stability and cleanliness of the alloy.

[0037] (3) To ensure the stability of chemical composition, a high vacuum of ≤0.1Pa is used for melting during vacuum self-consumption, which ensures the precise control of easily oxidized element Ti.

[0038] (4) The smelting method is relatively simple, and the equipment used is conventional special smelting equipment. The process is highly feasible, and there are no special requirements for the raw materials. The high temperature of the plasma induction furnace is used to rapidly melt tantalum metal, which improves efficiency and can further reduce production costs. The produced ingots have uniform composition and high quality stability. The macroscopic segregation index of Nb, Mo, Cr, Ta, and Ti elements is good, which meets the requirements for the use of the alloy. It has good prospects for industrial application and is worth promoting. Detailed Implementation

[0039] The present invention will be further described in detail below with reference to the embodiments. Example 1

[0040] The NbMoCrTaTi refractory high-entropy alloy was smelted using a 50kg vacuum induction furnace. The raw materials used were niobium bars (99.99%), molybdenum bars (99.99%), metallic chromium (99.6%), metallic tantalum (99.9%), and sponge titanium (99.6%). The chemical composition and target content of the NbMoCrTaTi refractory high-entropy alloy are shown in Table 1. The production steps include:

[0041] (1) Vacuum induction melting:

[0042] ①Put 3kg of metallic chromium, 9kg of niobium strips and 9.75kg of molybdenum strips into the prefabricated crucible of zirconium oxide in the vacuum induction furnace, and put 3.02kg of metallic chromium into the secondary hopper;

[0043] ② Evacuate to below 0.67 Pa, then start powering on to melt. After 2 hours, the chromium, niobium, and molybdenum bars in the crucible will melt completely.

[0044] ③ Add the remaining metallic chromium in batches from the silo. After all the metallic chromium has melted, raise the temperature to maintain the temperature of the molten metal at 1680℃, adjust it to a high vacuum of less than 0.05Pa, and degas for 20 minutes until [O] ≤ 10ppm, [N] ≤ 10ppm, and [H] ≤ 1ppm.

[0045] ④ Stop the vacuum, fill with 35000Pa of dried argon gas with a purity ≥99.99%, adjust the temperature to 1520℃, and pour the gas at a constant speed while energized;

[0046] ⑤ After the ingot cools to room temperature, demold it and cut it into thin strips; the size is 30×30mm. 2 .

[0047] (2) Plasma induction melting:

[0048] ① The cut niobium-molybdenum-chromium alloy strips, 21.085 kg of tantalum metal, and 3.6% of the total weight of slag in the plasma induction furnace are loaded into the zirconium oxide crucible. The plasma power supply is turned on, and the plasma medium gas is dried argon with a purity ≥99.99% and an argon flow rate of 120 L / min. Then the induction power supply is turned on to melt quickly.

[0049] ②After the furnace charge is completely melted, stop the plasma power supply, keep the lance blowing argon, remove the slag, and add 4.27kg of sponge titanium in batches. The amount of sponge titanium added each time should be enough to cover the surface of the molten metal. After all the sponge titanium has been completely melted, increase the induction power supply to stir the molten metal thoroughly.

[0050] ③ Adjust the temperature to 1450℃ and cast it into an alloy ingot with a specification of φ90m×680mm under electric current, which will be used as a consumable electrode.

[0051] (3) Vacuum consumable remelting:

[0052] ① The consumable electrode was annealed at 1200℃ for 16 hours.

[0053] ②After cooling to room temperature, polish the surface and then weld it onto the dummy electrode;

[0054] ③ Perform vacuum consumable remelting, maintaining a vacuum degree ≤0.1Pa and a melting rate of 90kg / h during the smelting process;

[0055] ④ After melting, when the surface temperature of the ingot reaches 650℃, demold the ingot and place it in an argon-protected furnace to cool slowly to 200℃ before removing it from the furnace.

[0056] After smelting, samples were taken from the bottom center, R / 4, R / 2, 3R / 4, and edges of the ingot for composition analysis (R: radius of the high-entropy alloy ingot). The results are as follows:

[0057] Table 1: Chemical composition and content (wt%) of high-entropy alloy ingot in Example 1

[0058]

[0059] Table 1 shows that after vacuum induction furnace smelting, plasma induction melting, and vacuum consumable melting, the FeCrCoNiAl high-entropy alloy ingot has excellent uniformity, and the macroscopic segregation indices of Nb, Mo, Cr, Ta, and Ti are between 0.97 and 1.02, which meets the requirements for use of the alloy. Example 2

[0060] The NbMoCrTaTi refractory high-entropy alloy was smelted using a 100kg vacuum induction furnace. The raw materials used were niobium bars (99.99%), molybdenum bars (99.99%), metallic chromium (99.6%), metallic tantalum (99.9%), and sponge titanium (99.6%). The chemical composition and target content of the NbMoCrTaTi refractory high-entropy alloy are shown in Table 2. The production steps include:

[0061] (1) Vacuum induction melting:

[0062] ①Put 5kg of metallic chromium, 22kg of niobium strips and 21.5kg of molybdenum strips into the prefabricated crucible of zirconium oxide in the vacuum induction furnace, and put 5.04kg of metallic chromium into the secondary hopper;

[0063] ② Evacuate to below 0.67 Pa, then begin melting. After 2.5 hours, the chromium, niobium, and molybdenum bars in the crucible will melt completely.

[0064] ③ Add metallic chromium in batches from the silo. After all the metallic chromium has melted, raise the temperature to maintain the temperature of the molten metal at 1660℃, adjust it to a high vacuum of less than 0.06Pa, and degas for 30 minutes until [O] ≤ 10ppm, [N] ≤ 10ppm, and [H] ≤ 1ppm.

[0065] ④ Stop the vacuum, fill with dried argon gas with a purity ≥99.99% at 60000Pa, adjust the temperature to 1550℃, and pour the gas at a constant speed while energized;

[0066] ⑤ After the ingot cools to room temperature, demold it and cut it into thin strips; the size is 50×50mm. 2 .

[0067] (2) Plasma induction melting:

[0068] ①Put the cut niobium-molybdenum-chromium alloy strips, 38.2kg of tantalum metal, and 5.0% of the total weight of slag into the zirconium oxide crucible of the plasma induction furnace. Turn on the plasma power supply. The plasma medium gas is dried argon with a purity ≥99.99% and an argon flow rate of 200L / min. Then turn on the induction power supply to melt quickly.

[0069] ②After the furnace charge is completely melted, stop the plasma power supply, keep the lance blowing argon, remove the slag, and add 8.53kg of sponge titanium in batches. The amount of sponge titanium added each time should be enough to cover the surface of the molten metal. After all the sponge titanium has been completely melted, increase the induction power supply to stir the molten metal thoroughly.

[0070] ③ Adjust the temperature to 1480℃ and cast it into an alloy ingot with a specification of φ100mm×900mm under electric current, which will be used as a consumable electrode.

[0071] (3) Vacuum consumable remelting:

[0072] ① Anneal the consumable electrode at a temperature of 1230℃ for 20 hours;

[0073] ②After cooling to room temperature, polish the surface and then weld it onto the dummy electrode;

[0074] ③ Perform vacuum consumable remelting, maintaining a vacuum degree ≤0.1Pa and a melting rate of 105kg / h during the smelting process;

[0075] ④ After melting, when the surface temperature of the ingot reaches 670℃, demold the ingot and place it in an argon-protected furnace to cool slowly to 190℃ before removing it from the furnace.

[0076] After smelting, samples were taken from the bottom center, R / 4, R / 2, 3R / 4, and edges of the ingot for composition analysis (R: radius of the high-entropy alloy ingot). The results are as follows:

[0077] Table 2: Chemical composition and content (wt%) of high-entropy alloy ingot in Example 2

[0078]

[0079] Table 2 shows that after vacuum induction furnace smelting, plasma induction melting, and vacuum consumable melting, the FeCrCoNiAl high-entropy alloy ingot has excellent uniformity, and the macroscopic segregation indices of Nb, Mo, Cr, Ta, and Ti are between 0.98 and 1.03, which meets the requirements for use of the alloy. Example 3

[0080] The NbMoCrTaTi refractory high-entropy alloy was smelted using a 50kg vacuum induction furnace. The raw materials used were niobium bars (99.99%), molybdenum bars (99.99%), metallic chromium (99.6%), metallic tantalum (99.9%), and sponge titanium (99.6%). The chemical composition and target content of the NbMoCrTaTi refractory high-entropy alloy are shown in Table 3. The production steps include:

[0081] (1) Vacuum induction melting:

[0082] ①Put 3kg of metallic chromium, 9.5kg of niobium strips and 10kg of molybdenum strips into the pre-made zirconia crucible of the vacuum induction furnace, and put 2.52kg of metallic chromium into the secondary hopper;

[0083] ② Evacuate to below 0.67 Pa, then start powering on to melt. After 2 hours, the chromium, niobium, and molybdenum bars in the crucible will melt completely.

[0084] ③ Add the remaining metallic chromium in batches from the silo. After all the metallic chromium has melted, raise the temperature to maintain the temperature of the molten metal at 1670℃, adjust it to a high vacuum of less than 0.05Pa, and degas for 25 minutes until [O] ≤ 10ppm, [N] ≤ 10ppm, and [H] ≤ 1ppm.

[0085] ④ Stop the vacuum, fill with 50000Pa of dried argon gas with a purity ≥99.99%, adjust the temperature to 1530℃, and pour the gas at a constant speed while energized;

[0086] ⑤ After the ingot cools to room temperature, demold it and cut it into thin strips; the size is 40×40mm. 2 .

[0087] (2) Plasma induction melting:

[0088] ①Place the cut niobium-molybdenum-chromium alloy strips, 19.85kg of tantalum metal, and 3.0% of the total weight of slag into the zirconium oxide crucible of the plasma induction furnace. Turn on the plasma power supply. The plasma medium gas is dried argon with a purity ≥99.99% and an argon flow rate of 160L / min. Turn on the induction power supply to melt quickly.

[0089] ②After the furnace charge is completely melted, stop the plasma power supply, keep the lance blowing argon, remove the slag, and add 5.27kg of sponge titanium in batches. The amount of sponge titanium added each time should be enough to cover the surface of the molten metal. After all the sponge titanium has been completely melted, increase the induction power supply to stir the molten metal thoroughly.

[0090] ③ Adjust the temperature to 1465℃ and cast it into an alloy ingot with a specification of φ90m×650mm under electric current, which will be used as a consumable electrode.

[0091] (3) Vacuum consumable remelting:

[0092] ① Anneal the consumable electrode at 1220℃ for 18 hours;

[0093] ②After cooling to room temperature, polish the surface and then weld it onto the dummy electrode;

[0094] ③ Perform vacuum consumable remelting, maintaining a vacuum degree ≤0.1Pa and a melting rate of 95kg / h during the smelting process;

[0095] ④ After the melting is completed, when the surface temperature of the ingot reaches 680℃, demold the ingot and place it in an argon-protected furnace to cool it slowly to 180℃ before removing it from the furnace.

[0096] After smelting, samples were taken from the bottom center, R / 4, R / 2, 3R / 4, and edges of the ingot for composition analysis (R: radius of the high-entropy alloy ingot). The results are as follows:

[0097] Table 3: Chemical composition and content (wt%) of high-entropy alloy ingot in Example 3

[0098]

[0099] Table 3 shows that after vacuum induction furnace smelting, plasma induction melting, and vacuum consumable melting, the FeCrCoNiAl high-entropy alloy ingot has excellent uniformity, and the macroscopic segregation indices of Nb, Mo, Cr, Ta, and Ti are between 0.96 and 1.03, which meets the requirements for use of the alloy. Example 4

[0100] The NbMoCrTaTi refractory high-entropy alloy was smelted using a vacuum induction furnace with a rated capacity of 250 kg. The raw materials used were niobium bars (99.99%), molybdenum bars (99.99%), metallic chromium (99.6%), metallic tantalum (99.9%), and sponge titanium (99.6%). The chemical composition and target content of the NbMoCrTaTi refractory high-entropy alloy are shown in Table 4. The production steps include:

[0101] (1) Vacuum induction melting:

[0102] ①Put 15kg of metallic chromium, 52.5kg of niobium strips and 51.25kg of molybdenum strips into the pre-made zirconia crucible of the vacuum induction furnace, and put 12.35kg of metallic chromium into the secondary hopper;

[0103] ② Evacuate to below 0.67 Pa, then start powering on to melt. After 3 hours, the chromium, niobium, and molybdenum bars in the crucible will melt completely.

[0104] ③ Add metallic chromium in batches from the silo. After all the metallic chromium has melted, raise the temperature to maintain the temperature of the molten metal at 1700℃, adjust it to a high vacuum of less than 0.05Pa, and degas for 25 minutes until [O] ≤ 10ppm, [N] ≤ 10ppm, and [H] ≤ 1ppm.

[0105] ④ Stop the vacuum, fill with dried argon gas with a purity ≥99.99% at 70000Pa, adjust the temperature to 1550℃, and pour the gas at a constant speed while energized;

[0106] ⑤ After the ingot cools to room temperature, demold it and cut it into thin strips; the size is 45×45mm. 2 .

[0107] (2) Plasma induction melting:

[0108] ①Put the cut niobium-molybdenum-chromium alloy strips, 96.7kg of tantalum metal, and 4.4% of the total weight of slag into the zirconium oxide crucible of the plasma induction furnace. Turn on the plasma power supply. The plasma medium gas is dried argon with a purity ≥99.99% and an argon flow rate of 180L / min. Turn on the induction power supply to melt quickly.

[0109] ②After the furnace charge is completely melted, stop the plasma power supply, keep the lance blowing argon, remove the slag, and add 23.84 kg of sponge titanium in batches. The amount of sponge titanium added each time should be enough to cover the surface of the molten metal. After all the sponge titanium has been completely melted, increase the induction power supply to fully stir the molten metal.

[0110] ③ Adjust the temperature to 1465℃ and cast it into an alloy ingot with a specification of φ145mm×1800mm under electric current, which will be used as a consumable electrode.

[0111] (3) Vacuum consumable remelting:

[0112] ① The consumable electrode was annealed at 1250℃ for 19 hours.

[0113] ②After cooling to room temperature, polish the surface and then weld it onto the dummy electrode;

[0114] ③ Perform vacuum consumable remelting, maintaining a vacuum degree ≤0.1Pa and a melting rate of 150kg / h during the smelting process;

[0115] ④ After melting, when the surface temperature of the ingot reaches 660℃, demold the ingot and place it in an argon-protected furnace to cool slowly to 190℃ before removing it from the furnace.

[0116] After smelting, samples were taken from the bottom center, R / 4, R / 2, 3R / 4, and edges of the ingot for composition analysis (R: radius of the high-entropy alloy ingot). The results are as follows:

[0117] Table 4: Chemical composition and content (wt%) of high-entropy alloy ingot in Example 4

[0118]

[0119] Table 4 shows that after vacuum induction furnace smelting, plasma induction melting, and vacuum consumable melting, the FeCrCoNiAl high-entropy alloy ingot has excellent uniformity, and the macroscopic segregation indices of Nb, Mo, Cr, Ta, and Ti are between 0.95 and 1.03, which meets the requirements for use of the alloy.

Claims

1. A method for smelting a refractory high-entropy alloy of NbMoCrTaTi, characterized in that, The chemical composition and mass percentage of the NbMoCrTaTi refractory high-entropy alloy are as follows: Nb 18-22%, Mo 19.5-21.5%, Cr 10-12%, Ta 38-42%, Ti 8.5-10.5%, with the balance being unavoidable impurity elements; the smelting method of the NbMoCrTaTi refractory high-entropy alloy includes the following steps: (1) Vacuum induction melting A. 50±5wt% metallic chromium, all niobium bars and molybdenum bars are loaded into a pre-made zirconium oxide crucible in a vacuum induction furnace and melted under vacuum by applying electricity; B. After the furnace charge has melted completely, add the remaining metallic chromium in batches. After all the charge has melted completely, raise the temperature and adjust it to a high vacuum for degassing until [O]≤10ppmw, [N]≤10ppmw, and [H]≤1ppmw. C. Stop the vacuum, fill with argon gas, adjust the temperature to 1520-1550℃, and pour the casting under power; D. After the ingot cools to room temperature, it is demolded and cut into thin strips to obtain niobium-molybdenum-chromium alloy strips; (2) Plasma induction melting E. Load the niobium-molybdenum-chromium alloy strip, tantalum metal, and slag (3-5% of the total weight of the metal material) into the zirconium oxide prefabricated crucible of the plasma induction furnace, and rapidly melt them by passing through the plasma power supply and induction power supply. F. After the furnace charge is completely melted, stop the plasma power supply, keep the lance blowing argon, remove the slag, add the sponge titanium in batches, and after all the sponge titanium is completely melted, increase the induction power supply to fully stir the molten metal. G. Adjust the temperature to 1450~1480℃, and cast the alloy ingot under electric current to be used as a consumable electrode; (3) Vacuum consumable remelting H. After annealing and polishing the consumable electrode, weld it onto the dummy electrode; I. Perform vacuum arc remelting, maintaining a melting rate of 90–150 kg / h; J. After melting, the ingot is demolded and placed in an argon-protected furnace for slow cooling.

2. The smelting method of the NbMoCrTaTi refractory high-entropy alloy according to claim 1, characterized in that: In step A, the vacuum degree during melting is ≤0.67Pa; in step B, the temperature is raised to the molten metal temperature of 1660~1700℃, and the vacuum degree during degassing is ≤0.06Pa.

3. The smelting method for the NbMoCrTaTi refractory high-entropy alloy according to claim 2, characterized in that: In step C, the pressure of argon gas introduced into the furnace is 35,000–70,000 Pa, and the argon gas is dried and has a purity ≥99.99%; in step D, the ingot is cut into 30×30–50×50 mm pieces. 2 Thin strips of the specified size.

4. The smelting method of the NbMoCrTaTi refractory high-entropy alloy according to claim 3, characterized in that: In step E, the plasma medium gas is argon gas with a purity of ≥99.99% and which has been dehydrated, and the flow rate is 120-200 L / min.

5. The smelting method of the NbMoCrTaTi refractory high-entropy alloy according to claim 4, characterized in that: In step F, the amount of sponge titanium added each time is sufficient to cover the surface of the molten metal; in step G, the length-to-diameter ratio of the casting mold is ≥6.

6. The smelting method of the NbMoCrTaTi refractory high-entropy alloy according to claim 5, characterized in that: In step H, the annealing temperature of the consumable electrode is 1200-1250℃, and the time is 16-20h.

7. The smelting method of the NbMoCrTaTi refractory high-entropy alloy according to claim 6, characterized in that: In step I, during vacuum self-consumable remelting, the vacuum level is maintained at ≤0.1 Pa.

8. The smelting method of the NbMoCrTaTi refractory high-entropy alloy according to any one of claims 1-7, characterized in that: In step J, the surface temperature of the ingot is ≥650℃ during demolding, and the ingot is slowly cooled to ≤200℃ before being taken out of the furnace.

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