Preparation method and 3D printing method of niobium-tungsten alloy spherical powder

Abstract

The invention discloses a preparation method of niobium-tungsten alloy spherical powder and a 3D printing method of the niobium-tungsten alloy spherical powder, and belongs to the technical field of refractory metal material preparation.The preparation method comprises the steps that niobium, tungsten, molybdenum and zirconium refractory metal raw materials are smelted to obtain cast ingots with uniform components, and hydride powder is formed after hydrotreating and mechanical crushing; spherical powder is prepared by adopting a plasma spheroidizing technology, then dehydrogenation is performed for 1-3 hours at the temperature of 450-750 DEG C, magnesium powder is added, treatment is performed for 2-5 hours in an inert atmosphere at the temperature of 800-1100 DEG C, and finally the low-oxygen niobium-tungsten alloy spherical powder with the oxygen content lower than 120 ppm is obtained. Compared with a traditional process, the spheroidizing treatment is innovatively carried out before the dehydrogenation and oxygen reduction process, the deoxidation efficiency is improved through the relatively small specific surface area of spherical powder, and oxygen content control is achieved in combination with magnesium powder heat treatment. The problems of high oxygen content and low powder yield in a traditional process are solved, and material support is provided for high-performance niobium-tungsten alloy components in the fields of aerospace, nuclear power and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of refractory metal material preparation, in particular to a preparation method of Nb-W alloy spherical powder and a 3D printing method thereof. BACKGROUND

[0002] As a new generation of high-temperature refractory metal material, Nb-W alloy has attracted much attention due to its excellent performance. The alloy has a high melting point (> 2400℃), excellent high-temperature strength (still maintaining 80% of room temperature strength at 1600℃), and low density characteristics (theoretical density 14.5 g / cm 3 ), making it the preferred material for extreme thermal environment components such as aerospace engine combustion chambers and rocket nozzles. However, its poor processability and low material utilization of traditional smelting-forging process severely restrict the application of complex components.

[0003] In recent years, additive manufacturing technology has broken through the limitations of traditional processes through digital layer-by-layer accumulation, providing new possibilities for the manufacture of complex components. However, the application of additive manufacturing technology is limited by the bottleneck of Nb-W alloy powder preparation. Existing powder preparation processes mainly use a three-step method of "hydrogenation crushing-dehydrogenation-spheroidization" (such as patents CN116352077A and CN119328154A). In the hydrogenation crushing stage, oxygen elements are easily solid-solved, and the subsequent dehydrogenation process cannot effectively remove interstitial oxygen, resulting in powder oxygen content exceeding 200 ppm. In addition, the "spheroidization and dehydrogenation" process (such as patent CN119194124A) avoids the defects of hydrogenation crushing, but does not combine with oxygen reduction treatment, with oxygen residual amount up to 300 ppm. The plasma spheroidization method (such as patent CN117428185B) can prepare high-quality powder, but due to the need for inert gas protection and high-energy consumption equipment, the cost of powder is high, and it is difficult to realize industrialized mass production.

[0004] The core defect of the existing technology is the redundancy of the process flow, and the independent dehydrogenation and oxygen reduction process increases the energy consumption by more than 30%. At the same time, the oxygen content control is insufficient, and the oxygen elements are solid-solved in the crushing stage in the traditional hydrogenation and dehydrogenation process, which is difficult to remove deeply in the subsequent treatment. Therefore, there is an urgent need for a low-cost, high-quality Nb-W alloy spherical powder preparation method suitable for additive manufacturing to meet the demand for high-performance materials in high-precision fields such as aerospace and nuclear power. SUMMARY

[0005] The present application is directed to the problems of high oxygen content, redundant process flow, and low powder yield in the existing preparation technology of niobium-tungsten alloy powder, and proposes a "spheroidization-dehydrogenation-oxygen reduction" synergistic process. The process performs dehydrogenation and oxygen reduction treatment after spheroidization treatment, significantly improves the oxygen reduction effect by using the larger contact area of spherical powder compared to irregular powder, and finally makes the oxygen content in the powder less than 120 ppm. The technical scheme provided by the present application is as follows: In one aspect, the present application provides a preparation method of niobium-tungsten alloy spherical powder, comprising the following steps: (1) Ingot melting: niobium (Nb), tungsten (W), molybdenum (Mo), and zirconium (Zr) refractory metal raw materials are weighed according to the preset component ratio, and then melted to obtain a niobium-tungsten alloy ingot with uniform composition; (2) Hydrogenation crushing: the niobium-tungsten alloy ingot obtained in step (1) is placed in a hydrogenation tank for hydrogenation treatment; after hydrogenation treatment, mechanical crushing is performed to obtain a niobium-tungsten alloy hydride powder; (3) Plasma spheroidization: the niobium-tungsten alloy hydride powder obtained in step (2) is subjected to plasma spheroidization treatment to obtain a niobium-tungsten alloy spherical powder; (4) Dehydrogenation treatment: the spheroidized niobium-tungsten alloy spherical powder is subjected to dehydrogenation treatment, the dehydrogenation temperature is 450-750℃, and the dehydrogenation time is 1-3h; (5) Oxygen reduction treatment: magnesium powder is added to the dehydrogenated niobium-tungsten alloy powder, and treated under inert gas at 800-1100℃ for 2-5h to finally obtain a low-oxygen niobium-tungsten alloy spherical powder.

[0006] In some specific embodiments, in step (1), the refractory niobium-tungsten alloy raw material has a component mass percentage of: tungsten 4.5-6.6%, molybdenum 1.6-2.8%, zirconium 0.7-1.6%, and the balance is niobium; The weighed refractory metal raw materials are loaded into a vacuum electromagnetic induction suspension melting furnace, vacuumed to below 2.0×10 -3 MPa and filled with argon gas protection, repeated melting at least 5 times, single time not less than 25min, to obtain a uniform composition ingot; then vacuum electron beam melting, temperature not higher than 3000℃, power 550-650kW, speed 80-150kg / h, single time not less than 30min.

[0007] In some specific embodiments, in step (2), the hydrogenation tank is first vacuumed to a vacuum degree not higher than 5×10 -2 Pa, then filled with hydrogen, the hydrogenation process temperature is controlled at 800-1000℃, the hydrogenation time is set to 1-3h, and the hydrogen pressure is maintained at 0.05-0.15MPa; The hydrogen content of the niobium-tungsten alloy hydride powder after hydrogenation is 0.1%-1.0%; and the particle size of the niobium-tungsten alloy hydride powder is 150-300 mesh.

[0008] In some specific embodiments, in step (3), the plasma side gas is argon, or a mixture of helium and argon, or a mixture of hydrogen and argon; wherein the flow rate of the plasma side gas is 40-75 L / min.

[0009] In some specific embodiments, the side gas is a mixture of hydrogen and argon, and the molar ratio of hydrogen to argon is 0.03-0.07:1, so that the niobium-tungsten alloy hydride powder undergoes hydrogen explosion during the spheroidization process, and the fine powder yield of the niobium-tungsten alloy spherical powder obtained is 70%-80%.

[0010] In some specific embodiments, in step (3), the particle size distribution of the niobium-tungsten alloy spherical powder includes two ranges of 15-53 μm and 45-105 μm, and the sphericity of the powder is ≥95%; The particle size of the powder with a particle size of 15-53 μm is obtained by adjusting the spheroidization process parameters to make the powder undergo hydrogen explosion during the spheroidization treatment of the hydride powder in step (3), and then screening the powder; The particle size of the powder with a particle size of 45-105 μm is obtained by shrinking the hydride powder during the spheroidization treatment in step (3).

[0011] In some specific embodiments, in step (3), the temperature of the plasma spheroidization treatment is 8000-12000℃, and the reaction pressure is 0.01-0.15 MPa.

[0012] In another aspect, the present application also provides a 3D printing method using the niobium-tungsten alloy spherical powder prepared by the above-mentioned niobium-tungsten alloy spherical powder preparation method, comprising the following steps: (1) 3D printing forming: forming a niobium-tungsten alloy printed product by laser selective melting forming and electron beam selective melting forming of the low-oxygen niobium-tungsten alloy spherical powder; (2) Heat treatment: heat treating the printed niobium-tungsten alloy printed product.

[0013] In some specific embodiments, in step (1), the power of the laser selective melting forming is 120-540 W, the scanning speed is 350-1000 mm / s, the laser strip spacing is 0.05-0.1 mm, and the powder laying thickness is 20-40 µm; The substrate preheating temperature of the electron beam selective melting forming is 600-900 DEG C, the beam current is 5-15 mA, the scanning speed is 250-750 mm / s, the melting interval is 0.05-0.2 mm, and the layer thickness is 25-55 mu m.

[0014] In some specific embodiments, in step (2), the temperature of the heat treatment is 600-1300 DEG C, and the holding time is 1-10 h.

[0015] With the technical scheme, the preparation method of the niobium-tungsten alloy spherical powder and the 3D printing method thereof have the following beneficial effects: 1. In the spheroidization process, a small amount of hydrogen is added to the plasma side gas, and the thermal conductivity of hydrogen is used to obtain more sufficient energy in the same time to completely spheroidize, and the spheroidization rate is improved, and the process makes the powder sphericity reach more than 99.5% (D90-D10 is less than 5 mu m); 2. The present application realizes the controllable explosion of hydrogenated niobium-tungsten by triggering the hydrogen explosion reaction through the precise control of the hydrogen element content (0.1%-1.0%) and the hydrogen-argon ratio (0.03-0.07:1) of the side gas in the plasma spheroidization process, so that the fine powder yield of the niobium-tungsten alloy spherical powder reaches 70%-80%; 3. The niobium-tungsten alloy material prepared by the present application has extremely low impurity element content and oxygen content, and the dehydrogenation and oxygen reduction process is carried out after spheroidization treatment, which improves the oxygen reduction effect; compared with irregularly shaped powder, the spherical powder has a larger specific surface area, so that the oxygen element can more efficiently escape from the surface of the powder during the oxygen reduction treatment, thereby realizing better oxygen reduction effect. After dehydrogenation and oxygen reduction treatment, the oxygen content of the finally obtained powder is below 120 ppm; 4. The high-purity low-oxygen niobium-tungsten alloy powder prepared by the present application is suitable for additive manufacturing processes such as selective laser melting (SLM) and electron beam selective melting (EBM), and the material prepared by 3D printing has high density and material elongation, and has good application prospect. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0017] The terms "one embodiment" or "an embodiment" as may appear herein are to be construed as referring to a particular feature, structure, or characteristic found in at least one implementation of the application. Throughout this specification, the terminology "upper", "lower", "top", "bottom", "over", "under" and the like, are used to aid the reader's understanding of the application by referring to the orientation of the figure or figures in which that feature is found, and thus, are not to be construed as limiting the application in any way. Furthermore, the terms "first", "second", and the like, merely denote different categories, and do not imply a particular order, sequence, or hierarchy, unless stated otherwise. It is to be understood that the data used herein can be interchangeable under appropriate circumstances, so that the embodiments of the application described herein are capable of operating in other sequences than those explicitly described. Embodiments of the application can be, for example, a process, a method, an article of manufacture, or an apparatus.

[0018] When a range of values is disclosed, unless otherwise stated, the endpoints of the ranges are included. Further, the range is inclusive of the minimum and maximum values, unless otherwise stated. Furthermore, where a range of values is provided, it is intended to include every value within that range, including the minimum and maximum values, unless otherwise stated. Additionally, it is intended that where a range of values is provided, it is intended to include every subrange between (and including) the minimum value of the range and the maximum value of the range, as well as to every combination of sub-ranges between (and including) the minimum and maximum values of the range. For example, the recitation "1 to 10" is intended to include the minimum value of 1 and the maximum value of 10, as well as any and all sub-ranges between (and including) the minimum and maximum values. Sub-ranges of the example range 1 to 10 include, but are not limited to, 1 to 6.1, 3.5 to 7.8, 5.5 to 10, etc.

[0019] The Nb-W alloy spherical powder preparation method provided by the embodiment of the application comprises the following steps: (1) Ingot melting: after the refractory metal raw materials of niobium (Nb), tungsten (W), molybdenum (Mo) and zirconium (Zr) are weighed according to the preset component proportion, the refractory metal raw materials are smelted to obtain a Nb-W alloy ingot with uniform components. Specifically, the Nb, W, Mo and Zr refractory metal raw materials with a purity greater than 99.9 wt.% are selected, and accurate weighing is completed according to the target alloy mass percentage (W 4.5-6.6%, Mo 1.6-2.8%, Zr 0.7-1.6%, and the balance is Nb); then the weighed refractory metal raw materials are loaded into a vacuum electromagnetic induction suspension smelting furnace, the furnace cavity is first vacuumized to a pressure not higher than 2.0×10 -3MPa, and argon is filled as a protective atmosphere to avoid oxidation during smelting; the electromagnetic induction suspension smelting system is started, and the raw material is repeatedly smelted for at least 5 times, and the single smelting time is not less than 25 min, so that the alloy elements are fully diffused and the composition is homogenized through multiple smelting, and a composition-uniform niobium-tungsten alloy ingot is obtained; in order to further improve the purity and uniformity of the ingot, the ingot needs to be treated by vacuum electron beam smelting, and the smelting temperature is controlled to be lower than 3000 ℃, the smelting power is 550-650 kW (specifically, it can be 550 kW, 600 kW, 650 kW), the smelting speed is 80-150 kg / h (specifically, it can be 80 kg / h, 100 kg / h, 120 kg / h, 150 kg / h), and the single smelting time is not less than 30 min, so that the high-uniformity and high-purity niobium-tungsten alloy ingot is finally prepared through the synergistic effect of electromagnetic induction suspension smelting and vacuum electron beam smelting.

[0020] (2) Hydrogenation crushing: the niobium-tungsten alloy ingot obtained in step (1) is placed in a hydrogenation tank for hydrogenation treatment; after the hydrogenation treatment, mechanical crushing is performed to obtain a niobium-tungsten alloy hydride powder. Specifically, the smelted niobium-tungsten alloy ingot is loaded into a hydrogenation tank, the hydrogenation tank is first evacuated to a predetermined vacuum degree, preferably 5x10 -2 Pa, and then hydrogen is filled. Under the conditions of a hydrogenation temperature of 800-1000 ℃ (specifically, it can be 800 ℃, 820 ℃, 850 ℃, 900 ℃, 950 ℃, 1000 ℃) and a hydrogen pressure of 0.05-0.15 MPa (specifically, it can be 0.05 MPa, 0.1 MPa, 0.15 MPa), the hydrogenation treatment is performed for 1-3 h (specifically, it can be 1 h, 2 h, 3 h), so that hydrogen atoms diffuse to the alloy matrix and react with the component elements to form hydrides. After the hydrogenation is completed, the niobium-tungsten alloy ingot is mechanically crushed for 0-60 min (specifically, it can be 20 min, 30 min, 40 min, 50 min, 60 min) to obtain irregularly shaped niobium-tungsten alloy hydride powder. Through the precise control of temperature, pressure and time, the content of hydrogen in the niobium-tungsten alloy can be stably controlled in the range of 0.1%-1.0% (specifically, it can be 0.1%, 0.4%, 0.5%, 0.7%, 0.8%, 0.83%, 0.87%, 1.0%), and the particle size range is 300-150 mesh (i.e., the particle size distribution is between 150 mesh and 300 mesh).

[0021] (3) Plasma spheroidization: the niobium-tungsten alloy hydride powder obtained in step (2) is subjected to plasma spheroidization treatment to obtain a niobium-tungsten alloy spherical powder. Specifically, the niobium-tungsten alloy hydride powder is loaded into a feeder of a radio frequency plasma spheroidization device, the inside of the device is first subjected to vacuum treatment to remove residual gas, and then an inert gas (usually argon) is filled to establish a basic atmosphere; under the protection of a carrier gas (preferably argon, with a flow rate of 2-6 L / min, specifically 2 L / min, 4 L / min, 6 L / min), the niobium-tungsten alloy hydride powder is delivered to a plasma region with a temperature of 8000-12000°C (specifically 8000°C, 10000°C, 12000°C) at a feeding rate of 0.1-100 g / min (specifically 0.1 g / min, 10 g / min, 40 g / min, 50 g / min, 100 g / min), the powder rapidly melts to form droplets in the high-temperature plasma environment, the droplets condense into spherical particles under the action of surface tension and fall into a powder collector, thereby obtaining a niobium-tungsten alloy spherical powder; during the process, the power of the plasma spheroidization device is controlled at 15-100 kW (specifically 15 kW, 40 kW, 50 kW, 100 kW), the reaction pressure is 0.01-0.15 MPa (specifically 0.01 MPa, 0.08 MPa, 0.15 MPa), the center gas (argon) flow rate is 10-25 L / min (specifically 10 L / min, 17.5 L / min, 20 L / min, 25 L / min), and the plasma side gas is a mixture of argon or helium and argon, hydrogen and argon, wherein the molar ratio of hydrogen and argon is preferably 0.03-0.07:1 (specifically 0.03:1, 0.05:1, 0.07:1), the overall flow rate of the side gas is 40-75 L / min (specifically 40 L / min, 55 L / min, 57.5 L / min, 75 L / min), and the reaction chamber pressure is maintained at 12.5-15 psi (specifically 12.5 psi, 13.75 psi, 15 psi); to further improve the purity and dispersity of the powder, the spherical powder needs to be cleaned (deionized water cleaning for 3-4 times) and dried (vacuum environment drying at 80-160°C for 0.5-2 h); through precise control of the above temperature, pressure, feeding rate, carrier gas and side gas parameters, efficient spheroidization of the niobium-tungsten alloy hydride powder in the high-temperature plasma can be achieved, and the final prepared niobium-tungsten alloy spherical powder has a particle size of 15-53 μm and 45-105 μm, and a sphericity of ≥95%.

[0022] (4) Dehydrogenation treatment: the spheroidized niobium-tungsten alloy spherical powder is subjected to dehydrogenation treatment, the dehydrogenation temperature is 450-750°C, and the dehydrogenation time is 1-3h. Specifically, the spheroidized niobium-tungsten alloy spherical powder is loaded into a dehydrogenation furnace, the vacuum system is first started to perform vacuumization treatment on the furnace cavity, until the vacuum degree in the furnace is not higher than 5x10 -2 Pa to create a low hydrogen partial pressure environment; then the dehydrogenation heating system is started, and the vacuum state is continuously maintained during the dehydrogenation process, so as to promote the desorption and discharge of residual hydrogen (from the previous hydrogenation crushing process) in the powder through the vacuum negative pressure effect; the specific dehydrogenation process parameters are: the dehydrogenation temperature is controlled in the range of 450-750°C (specifically, 450°C, 550°C, 650°C, 750°C), and the dehydrogenation time is set to 1-3 hours (specifically, 1h, 2h, 3h); after the dehydrogenation reaction is completed, argon is filled into the furnace cavity to a pressure of 0.1-0.2MPa (specifically, 0.1MPa, 0.15MPa, 0.2MPa), and the inert atmosphere of argon is used to isolate air to prevent the powder from being oxidized during the cooling process; finally, the cooling rate is 5-15°C / min (specifically, 5°C / min, 10°C / min, 15°C / min), so that the temperature in the furnace is reduced to room temperature, and the dehydrogenated niobium-tungsten alloy powder is taken out; through the synergistic effect of "vacuum desorption-inert protection- slow cooling", the hydrogen content in the powder is effectively reduced, the risk of hydrogen embrittlement is avoided, and the sphericity and particle size distribution of the powder are stable.

[0023] (5) Oxygen reduction treatment: magnesium powder is added to the niobium-tungsten alloy powder after dehydrogenation treatment, and the mixture is treated in an inert gas at 800-1100°C for 2-5h to obtain low-oxygen niobium-tungsten alloy spherical powder. Specifically, magnesium powder (as a deoxidizer) is added to the spheroidized niobium-tungsten alloy spherical powder in a certain proportion, and the preferred amount is 0.1% (mass fraction), and the mixed powder is placed in an inert gas (such as argon) protection environment, heated to 800-1100°C (specifically, 800°C, 900°C, 1000°C, 1100°C) and kept for 2-5h (specifically, 2h, 3h, 4h, 5h); in this process, the magnesium powder acts as a strong reducing agent and reacts with the oxygen on the surface and inside of the powder at high temperature (such as 2Mg + O2→ 2MgO), converting the oxygen into magnesium oxide (MgO) and separating from the matrix; the inert gas environment effectively isolates air to prevent secondary oxidation of the magnesium powder or the niobium-tungsten alloy at high temperature; after the holding is completed, the furnace is cooled to room temperature, and the generated magnesium oxide impurities are separated and removed through screening and other processes, finally obtaining low-oxygen niobium-tungsten alloy spherical powder with reduced oxygen content; through the synergistic effect of magnesium hot reduction reaction and inert atmosphere protection, the process effectively controls the oxygen content of the powder while maintaining the integrity of the spherical powder morphology.

[0024] In some specific embodiments, in step (1), the refractory niobium-tungsten alloy raw material has the following composition by mass percentage: 4.5-6.6% tungsten, 1.6-2.8% molybdenum, 0.7-1.6% zirconium, and the balance niobium; The weighed refractory metal raw material is loaded into a vacuum electromagnetic induction levitation melting furnace, vacuumed to below 2.0 x 10 -3 MPa and filled with argon protection, repeated at least 5 times, single time not less than 25 min, to obtain a composition uniform ingot; and then vacuum electron beam melting at a temperature not higher than 3000℃, a power of 550-650kW, a speed of 80-150kg / h, and a single time not less than 30 min. Specifically, through the synergistic effect of "electromagnetic induction levitation melting + vacuum electron beam melting", a high-uniformity and high-purity ingot can be prepared. First, vacuum electromagnetic induction levitation melting is adopted, vacuumed (below 2.0 x 10 -3 MPa) and protected by argon to avoid oxidation, combined with repeated melting (single melting time ≥ 25 min) for at least 5 times (specifically 5, 6, 7 times), to promote the full diffusion of refractory elements (W, Mo, Zr), eliminate initial composition segregation, and obtain a composition uniform ingot; then vacuum electron beam melting is performed, through high-energy electron beam bombardment (melting temperature below 3000℃, electron beam power 550-650kW, melting speed 80-150kg / h, single melting time ≥ 30 min), to realize deep purification (remove residual low-melting-point impurities) and microstructure control (suppress macroscopic segregation and refine grains); finally, the prepared ingot has high composition uniformity and high purity, and through precise control of the multi-stage melting process parameters, the uniform distribution of refractory elements is effectively regulated and the impurity content is controlled.

[0025] In some specific embodiments, in step (2), the hydrogenation tank is first vacuumed to a vacuum degree not higher than 5 x 10 -2 Pa, and then filled with hydrogen, the hydrogenation process is controlled at a temperature of 800-1000℃, the hydrogenation time is set to 1-3h, and the hydrogen pressure is maintained at 0.05-0.15MPa; After hydrogenation and crushing, the hydrogen content in the niobium-tungsten alloy hydride powder is 0.1%-1.0%; and the particle size of the niobium-tungsten alloy hydride powder is 150-300 mesh.

[0026] Specifically, the hydrogenation tank is first vacuumed to a vacuum degree not higher than 5 x 10 -2Pa, and then hydrogen is filled, the temperature of the hydrogenation process is accurately controlled at 800-1000℃ (specifically, 800℃, 850℃, 950℃, 1000℃), the hydrogenation time is set to 1-3h (specifically, 1h, 2h, 3h), and the hydrogen pressure is stably maintained at 0.05-0.15MPa (specifically, 0.05MPa, 0.10MPa, 0.15MPa); after hydrogenation crushing, the hydrogen element content in the obtained niobium-tungsten alloy hydride powder is accurately controlled at 0.1%-1% (specifically, 0.1%, 0.4%, 0.5%, 0.7%, 0.8%, 0.83%, 0.87%, 1.0%), and the powder particle size distribution is 150-300mesh (i.e. 48-106μm, specifically, 300mesh (48μm), 200mesh (75μm), 150mesh (106μm)); in this process, the high vacuum environment effectively isolates air to avoid the invasion of impurity elements such as oxygen and nitrogen during hydrogenation; the hydrogenation temperature of 800-1000℃ and the hydrogen pressure of 0.05-0.15MPa synergistically promote the diffusion and penetration of hydrogen atoms into the niobium-tungsten alloy lattice, so that the hydrogen element is fully solid-solved in the metal matrix to form stable hydrides (such as NbW2HX); the hydrogenation time of 1-3h ensures that the reaction reaches dynamic equilibrium, accurately controls the hydrogen element content in the best interval of 0.1%-1.0%, guarantees the controllability of the hydrogen explosion reaction in the subsequent spheroidization process (avoids insufficient crushing due to too low hydrogen element content or abnormal expansion caused by too high hydrogen element content), and reserves reasonable reaction space for the dehydrogenation process; the particle size distribution of 150-300mesh is accurately regulated by the mechanical action of hydrogenation crushing, improves the uniformity of the hydride powder particle size, and then improves the melting uniformity and spheroidization efficiency during the subsequent plasma spheroidization, while avoiding the agglomeration problem caused by too fine particles (<300mesh) or the incomplete spheroidization defects caused by too coarse particles (>150mesh).

[0027] In some specific embodiments, in step (3), the plasma side gas is argon, or a mixture of helium and argon, or a mixture of hydrogen and argon; wherein the plasma side gas flow is 40-75L / min; specifically, when argon is used as the protective gas, its low ionization energy characteristic can stably maintain the plasma column shape and uniform temperature field, providing a stable melting environment for the powder; when helium-argon mixed gas is used, helium not only enhances the plasma energy density to enhance the powder heating efficiency, but also accelerates the cooling of the molten layer, promotes the rapid formation of spherical crystal nuclei and reduces satellite ball defects; hydrogen-argon mixed gas utilizes the reducing property and low density characteristics of hydrogen, which not only promotes the formation of spherical crystal nuclei through H+O reaction (such as H+O→OH - +H +) to reduce the disturbance to the plasma column to maintain the uniformity of the energy distribution; precise control of the flow rate of 40-75 L / min ensures the plasma column confinement effect, avoiding energy loss caused by too low flow rate or excessive cooling (insufficient spheroidization) caused by too high flow rate. Through the synergistic optimization of gas type, mixing ratio and flow rate, the plasma energy field and the powder melting-solidification process are precisely matched, and finally high-quality niobium-tungsten alloy spherical powder with high spheroidization degree is obtained.

[0028] In some specific embodiments, the side gas is a mixed gas of hydrogen and argon, and the molar ratio of hydrogen to argon is 0.03-0.07:1, so that the niobium-tungsten alloy hydride powder undergoes hydrogen explosion during spheroidization, and the fine powder yield of the niobium-tungsten alloy spherical powder is 70%-80%. Specifically, in step (2), the hydrogen element content of the raw material niobium-tungsten alloy hydride powder is precisely controlled to be 0.1%-1.0% during the hydrogenation crushing process, and the mixed side gas (molar ratio of hydrogen to argon is 0.03-0.07:1, specifically 0.03:1, 0.05:1, 0.07:1) of hydrogen and argon is used for plasma spheroidization treatment, and the hydrogen explosion effect is used to realize efficient spheroidization and fine powder yield improvement; under the protection of argon gas environment, trace amount of hydrogen in the side gas and lattice hydrogen (NbW2HX) in the niobium-tungsten alloy hydride react synergistically at high temperature plasma, hydrogen molecules (H2) are dissociated into active hydrogen atoms (H) under the action of high-energy electrons in plasma, and combine with lattice oxygen (O 2- ) in the hydride to generate volatile water vapor (H2O↑), while releasing a large amount of heat to form a local high-temperature micro area, promoting the powder particles to undergo violent thermal explosion (hydrogen explosion), realizing particle crushing and spherical reconstruction; this process does not need a pre-dehydrogenation step, directly uses the synergistic effect of raw material hydrogen element content (0.1%-1.0%) and side gas hydrogen to form a dynamic balance hydrogen explosion reaction in the plasma energy field, so that the powder particles spontaneously crush into spherical powder with uniform particle size during the melting-solidification process, the fine powder yield is 70%-80%, which is significantly improved, while the oxygen content is reduced, the spheroidization degree is improved, the production cost is reduced, and the process flow is simplified (1-2 dehydrogenation processes are reduced); this technology realizes efficient and controllable hydrogen explosion reaction through precise matching of raw material hydrogen element content and molar ratio of side gas hydrogen (0.03-0.07:1) and synergistic regulation of high-temperature plasma environment, ensuring the high quality of the spheroidized powder and the economy of the process.

[0029] In some specific embodiments, in step (3), the particle size distribution of the niobium-tungsten alloy spherical powder includes two ranges of 15-53 μm and 45-105 μm, and the spheroidization degree of the powder is ≥95%; The powder with a particle size of 15-53 μm is a powder obtained by hydrogen explosion of the hydride powder in the spheroidization process in step (3) and subsequent screening treatment. The powder with a particle size of 45-105 μm is a powder obtained by shrinkage of the hydride powder in the spheroidization process in step (3). Specifically, the fine powder interval of 15-53 μm precisely matches the requirement of the selective laser melting (SLM) process for high-precision powder laying (the process layer thickness is usually 20-40 μm), which can effectively reduce the risk of powder agglomeration and improve the uniformity of powder laying; the coarse powder interval of 45-105 μm adapts to the high-melt pool temperature characteristics of the electron beam selective melting (EBM) process, which can reduce the loss of fine powder flying and also consider the printing efficiency; the synergistic coverage of the two particle size ranges (15-53 μm and 45-105 μm) makes the powder flexible to be applied to different additive manufacturing equipment (SLM and EBM), which expands the process applicability; at the same time, the powder with a sphericity of ≥95% (high sphericity feature) provides more active sites for subsequent dehydrogenation and oxygen reduction treatment due to the increased specific surface area compared with irregular particles, thereby effectively reducing the impurity elements and oxygen content.

[0030] In some specific embodiments, in step (3), the temperature of the plasma spheroidization treatment is 8000-12000℃, and the reaction pressure is 0.01-0.15 MPa. Specifically, in the plasma spheroidization treatment, the temperature is precisely set to 8000-12000℃ (specifically, 8000℃, 10000℃, or 12000℃), and the reaction pressure is controlled to be 0.01-0.15 MPa (specifically, 0.01 MPa, 0.08 MPa, or 0.15 MPa); wherein the plasma temperature of 8000-12000℃ (far exceeding the melting point of tungsten 3422℃ and the melting point of niobium 2477℃) makes the powder particles quickly complete the melting-surface tension dominated spheroidization process, reduces the surface roughness, and effectively inhibits grain coarsening, forming a dense and defect-free spherical structure; the low-pressure environment of 0.01-0.15 MPa effectively reduces the interaction between the plasma and the air, reduces the oxidation pollution of the powder by oxygen partial pressure, and reduces the oxygen content of the spheroidized powder; the matching of high temperature and low pressure forms a rapid cooling environment, inhibits the generation of non-equilibrium phases, and finally makes the sphericity of the powder reach more than 95%.

[0031] The embodiment of the present application also provides a 3D printing method using the niobium-tungsten alloy spherical powder prepared by the above-mentioned niobium-tungsten alloy spherical powder preparation method, comprising the following steps: (1) 3D printing forming: Low-oxygen niobium-tungsten alloy spherical powder is formed into niobium-tungsten alloy printed products by laser selective melting forming and electron beam selective melting forming. Specifically, low-oxygen niobium-tungsten alloy spherical powder is used for laser selective melting forming (SLM) and electron beam selective melting forming (EBM), respectively. By precisely controlling the forming process parameters, including laser power, scanning speed, layer thickness, electron beam energy density, etc., high-performance niobium-tungsten alloy printed products with complex structures are prepared. After forming, the density of the formed parts is detected by Archimedes drainage method, X-ray computed tomography (CT), etc. to ensure that there are no obvious defects in the interior and the density is close to the theoretical value. At the same time, the mechanical properties of the formed parts are tested by using universal material testing machine, hardness tester and other equipment, including tensile strength, yield strength, elongation, hardness and other indicators to evaluate their performance in actual application.

[0032] (2) Heat treatment: The printed niobium-tungsten alloy printed products are heat treated. Specifically, the printed niobium-tungsten alloy printed products are placed in a high-temperature furnace for heat treatment to optimize their microstructure and mechanical properties. First, according to the composition of the alloy and the expected performance, the appropriate heat treatment temperature and holding time are determined. Preferably, the heat treatment temperature ranges from 600-1300°C, and the holding time ranges from 1h to several h. During the heat treatment process, inert gas (such as argon) is used for protection to prevent oxidation and contamination. After the heat treatment is completed, it is slowly cooled to room temperature to reduce residual stress.

[0033] In some specific embodiments, in step (1), the power of laser selective melting forming is 120-540W, the scanning speed is 350-1000mm / s, the laser strip spacing is 0.05-0.1mm, and the powder laying thickness is 20-40µm. The substrate preheating temperature of electron beam selective melting forming is 600-900°C, the beam current is 5-15mA, the scanning speed is 250-750mm / s, the melting spacing is 0.05-0.2mm, and the layer thickness is 25-55µm.

[0034] The process parameters of selective laser melting (SLM) forming are: laser power 120-540 W (specifically, 120 W, 240 W, 300 W, 540 W), scanning speed 350-1000 mm / s (specifically, 350 mm / s, 500 mm / s, 600 mm / s, 1000 mm / s), laser strip spacing 0.05-0.1 mm (specifically, 0.05 mm, 0.06 mm, 0.08 mm, 0.1 mm), powder laying thickness 20-40 μm (specifically, 20 μm, 30 μm, 40 μm); the niobium-tungsten alloy powder with a particle size of 15-53 μm is selected, and the 3D printing process of selective laser melting (SLM) is used for forming; the synergy of laser power and scanning speed ensures deep penetration and effectively suppresses heat accumulation, avoiding grain coarsening; the narrow spacing design of laser strip spacing effectively reduces un-melted defects and improves surface roughness; the thin layer control of powder laying thickness reduces interlayer stress, and the combination of interlayer rotation strategy further suppresses the expansion of interlayer cracks. The process parameters of electron beam selective melting (EBM) forming are: substrate preheating temperature 600-900 ℃ (specifically, 600 ℃, 750 ℃, 900 ℃), beam current 5-15 mA (specifically, 5 mA, 10 mA, 15 mA), scanning speed 250-750 mm / s (specifically, 250 mm / s, 500 mm / s, 700 mm / s, 750 mm / s), melting spacing 0.05-0.2 mm (specifically, 0.05 mm, 0.1 mm, 0.2 mm), layer thickness 25-55 μm (specifically, 25 μm, 40 μm, 45 μm, 55 μm); the niobium-tungsten alloy powder with a particle size of 45-105 μm is selected, and the 3D printing process of electron beam selective melting (EBM) is used for forming; the thermodynamic regulation is used to strengthen the forming quality; the substrate preheating (600-900 ℃) reduces the thermal stress gradient and suppresses deformation, while reducing the solidification speed of the molten pool and promoting the generation of nano precipitates; the synergy of beam current and scanning speed (high beam current ensures the depth of the molten pool, and medium-speed scanning balances the stability of the molten pool) reduces pores.

[0035] In some specific embodiments, in step (2), the temperature of the heat treatment is 600-1300 ℃, and the holding time is 1-10 h. Specifically, the printed niobium-tungsten alloy product is subjected to heat treatment, the heat treatment temperature is 600-1300 ℃ (specifically, 1100 ℃, 1200 ℃, 1300 ℃), and the holding time is 1-10 h (specifically, 1 h, 3 h, 6 h, 10 h); the heat treatment process effectively eliminates the residual stress generated in the printing process, optimizes the microstructure of the alloy, improves the mechanical properties, and ensures that the comprehensive performance of the niobium-tungsten alloy product meets the application requirements by precisely controlling the temperature and holding time.

[0036] The following detailed description of examples of the present application is illustrative only and is not intended to be limiting of the application.

[0037] Example 1 A method for preparing a niobium-tungsten alloy spherical powder, comprising the following steps: (1) Ingot melting After the refractory metal raw materials of Nb, W, Mo and Zr are accurately weighed according to the target alloy mass percentage (6.0% W, 1.9% Mo, 1.2% Zr, and the balance of Nb), the raw materials are melted by a vacuum electromagnetic induction suspension melting furnace. The furnace chamber is first evacuated to 2.0 x 10 -3 MPa, and then argon is filled as a protective atmosphere. The raw materials are repeatedly melted for 7 times (single melting time is 30 min). Subsequently, the raw materials are further melted by a vacuum electron beam, the melting temperature is 3000℃, the melting power is 650kW, the melting speed is 100kg / h, and the melting time is 30 min each time, to obtain a niobium-tungsten alloy ingot with uniform composition.

[0038] (2) Hydrogenation crushing The niobium-tungsten alloy ingot obtained by melting is loaded into a hydrogenation tank. The hydrogenation tank is first evacuated to 5 x 10 -2 Pa, and then hydrogen is filled. The hydrogenation temperature is 900℃, the hydrogenation time is 3h, and the hydrogen pressure is maintained at 0.10MPa. Subsequently, the hydrogenated niobium-tungsten alloy ingot is mechanically crushed for 50s, and the crushed product is sieved to obtain a niobium-tungsten alloy hydride powder. The hydrogen content in the obtained powder is 0.80% by detection.

[0039] (3) Plasma spheroidization The hydrogenated broken niobium-tungsten alloy hydride powder is loaded into the feeder of the radio frequency plasma spheroidization device, the inside of the device is first vacuumized to remove residual gas, and then argon is filled to establish a basic atmosphere; under the protection of the carrier gas argon (flow rate of 4.0 L / min), the niobium-tungsten alloy hydride powder is transported to the plasma region with a temperature of 10000℃ at a feeding rate of 40 g / min, the center gas argon flow rate is 20 L / min, the plasma side gas is a mixed gas of argon and hydrogen (molar ratio of hydrogen to argon is 0.04:1), the overall flow rate of the side gas is 55 L / min, the reaction chamber pressure is 15 psi, and the plasma power is 40 kW; then the niobium-tungsten alloy powder is sent into the high-temperature zone at the center of the plasma torch using the carrier gas, the powder rapidly melts to form droplets in the high-temperature plasma environment, and condenses into spherical particles under the action of surface tension, thereby obtaining niobium-tungsten alloy spherical powder with extremely high sphericity; the spherical niobium-tungsten alloy powder is washed in deionized water for 4 times, then dried at 100℃ for 1 h under a nitrogen protective atmosphere, and high-purity niobium-tungsten alloy spherical powder in two particle size ranges of 15-53 μm and 45-105 μm is obtained through screening treatment, wherein the fine powder yield is 80%, and the sphericity is 99.5%.

[0040] (4) Dehydrogenation treatment The spheroidized niobium-tungsten alloy spherical powder is loaded into a degassing furnace, and the vacuum furnace is first vacuumized to 5×10 - 2 Pa to create a low hydrogen partial pressure environment, and then the dehydrogenation reaction is completed at a temperature of 600℃ for 3 h; after the dehydrogenation reaction is completed, argon is filled into the furnace cavity to a pressure of 0.2 MPa, and the inert atmosphere of argon is used to isolate air, and then cooled to room temperature at a cooling rate of 10℃ / min, and finally the niobium-tungsten alloy spherical powder with low hydrogen content is obtained.

[0041] (5) Oxygen reduction treatment The dehydrogenated niobium-tungsten alloy spherical powder is subjected to oxygen reduction treatment, and magnesium powder is added as a deoxidizer in the crucible at a proportion of 0.1% of the mass of the powder before oxygen reduction, and treated at a temperature of 800℃ for 3 h, and finally low-oxygen niobium-tungsten alloy spherical powder is obtained; detection shows that the oxygen content of the low-oxygen niobium-tungsten alloy spherical powder in two particle size ranges of 15-53 μm and 45-105 μm is 120 ppm and 80 ppm, respectively.

[0042] The aforementioned niobium-tungsten alloy spherical powder is selected for 3D printing method, including the following steps: (1) 3D printing forming Nb-W alloy powder with a particle size of 15-53 µm was selected and formed into a printed product by selective laser melting. The powder laying thickness was 30 µm, the laser power was 240 W, the laser scanning speed was 500 mm / s, and the laser strip spacing was 0.06 µm. Nb-W alloy powder with a particle size of 45-105 µm was selected and formed into a printed product by electron beam selective melting. The beam current was 10 mA, the scanning speed was 700 mm / s, the melting spacing was 0.1 mm, and the layer thickness was 45 µm.

[0043] (2) Heat treatment The printed Nb-W alloy printed product was heat treated at a temperature of 1300 °C for 3 h.

[0044] Example 2 The Nb-W alloy spherical powder was prepared according to the method of Reference Example 1, except that in step (1), the weighed refractory metal raw materials were only subjected to vacuum electromagnetic induction suspension melting furnace melting.

[0045] Example 3 The Nb-W alloy spherical powder was prepared according to the method of Reference Example 1, except that in step (1), the weighed refractory metal raw materials were only subjected to vacuum electron beam melting.

[0046] Example 4 The Nb-W alloy spherical powder was prepared according to the method of Reference Example 1, except that in step (2), the hydrogenation temperature was controlled at 800 °C, the hydrogenation time was set to 2 h, the hydrogen pressure was maintained at 0.05 MPa, and the hydrogen content of the prepared powder was 0.85%; after plasma spheroidization in step (3), the sphericity was 96.3%, and the fine powder yield was 72%.

[0047] Example 5 The Nb-W alloy spherical powder was prepared according to the method of Reference Example 1, except that in step (2), the hydrogenation temperature was controlled at 1000 °C, the hydrogenation time was set to 1 h, the hydrogen pressure was maintained at 0.15 MPa, and the hydrogen content of the prepared powder was 0.87%; after plasma spheroidization in step (3), the sphericity was 95.8%, and the fine powder yield was 70%.

[0048] Example 6 The Nb-W alloy spherical powder was prepared according to the method of Reference Example 1, except that the plasma side gas was argon, the side gas flow rate was 45 L / min, the fine powder yield was 30.0%, and the sphericity was 93.4%.

[0049] Example 7 The method of preparing the spherical Nb-W alloy powder of Reference Example 1 was followed, except that the plasma side gas was a mixture of argon and helium, and the total flow rate of the side gas was 45 L / min. The fine powder yield was 45.0%, and the sphericity was 97.5%.

[0050] Example 8 The method of preparing the spherical Nb-W alloy powder of Reference Example 1 was followed, except that the plasma side gas was a mixture of argon and hydrogen (the molar ratio of hydrogen to argon was 0.03:1), and the total flow rate of the side gas was 45 L / min. The fine powder yield was 78.2%, and the sphericity was 98.6%.

[0051] Example 9 The method of preparing the spherical Nb-W alloy powder of Reference Example 1 was followed, except that the plasma side gas was a mixture of argon and hydrogen (the molar ratio of hydrogen to argon was 0.01:1), and the total flow rate of the side gas was 45 L / min. The fine powder yield was 76.5%, and the sphericity was 98.1%.

[0052] Example 10 The 3D printing method of Reference Example 1 was followed, except that in the 3D printing process, in step (2), the heat treatment temperature was 1100°C, and the holding time was 5 h.

[0053] Example 11 The 3D printing method of Reference Example 1 was followed, except that in the 3D printing process, in step (2), the heat treatment temperature was 1200°C, and the holding time was 2 h.

[0054] Comparative Example 1 The method of preparing the spherical Nb-W alloy powder of Reference Example 1 was followed, except that after step (2), the dehydrogenation treatment of step (4) and the oxygen reduction treatment of step (5) were directly performed.

[0055] Test Example For Examples 1-11 and Comparative Example 1, the hydrogen content of the niobium-tungsten alloy hydride powder obtained after hydrogenation crushing in Step (2) was tested, and the specific value was accurately determined by professional means such as thermogravimetric analysis (TGA), vacuum heating degassing method, or inert gas melting-thermal conductivity / infrared detection method. The results reflect the solid solution and combined state of hydrogen in the niobium-tungsten alloy hydride, which is a key parameter affecting the subsequent dehydrogenation spheroidization process and powder performance. The spherical niobium-tungsten alloy powder obtained was further tested for sphericity and fine powder yield. The sphericity was quantitatively evaluated by image analysis or optical microscopy of the powder particle profile and the degree of agreement with the ideal spherical surface. High sphericity generally means excellent flowability and packing performance. The fine powder yield was defined as the mass percentage of powder within the target particle size range in the total output powder, directly reflecting the retention efficiency of fine particles in the spheroidization process. At the same time, the 15-53 μm and 45-105 μm particle size range of the spherical niobium-tungsten alloy powder was selected, and after 3D printing technology, the printed products were subjected to systematic performance testing and analysis. The oxygen content was determined by oxygen-nitrogen analyzer to evaluate the material toughness and high temperature performance, the density was measured by Archimedes drainage method or X-ray CT technology to reflect the mechanical and corrosion resistance properties, the hardness was tested by hardness tester to evaluate the wear resistance, and the tensile strength and elongation were obtained by tensile test by universal material testing machine to characterize the maximum stress and plastic deformation capacity of the material, respectively, so as to fully reveal the influence of process parameters on the characteristics of the powder and the comprehensive performance of the final product. Among them, the hydrogen content of the niobium-tungsten alloy hydride powder obtained after hydrogenation crushing in Step (2) is shown in Table 1, the sphericity and fine powder yield of the spherical niobium-tungsten alloy powder are shown in Table 2, the detailed performance data of the 15-53 μm particle size powder 3D printed product are shown in Table 3, and the detailed performance data of the 45-105 μm particle size powder 3D printed product are shown in Table 4.

[0056] Table 1

[0057] Table 2

[0058] Table 3

[0059] Table 4

[0060] The system test of examples 1-11 and comparative example 1 shows that: the composition uniformity of the niobium-tungsten alloy ingot prepared in example 1 is the best. The ingot is subjected to hydrogenation crushing treatment (900 DEG C for 3 hours, hydrogen pressure 0.10 MPa, and the final hydrogen content is 0.80%), and the niobium-tungsten alloy hydride powder is obtained; then through the plasma spheroidization process, based on the accurate control of the hydrogen content of the raw material 0.8% and the hydrogen to argon ratio of the side gas, the hydrogen explosion reaction is triggered to realize the controllable explosion of the hydrogenated niobium-tungsten, and finally the spherical powder with a spherical degree of 99.5% and a fine powder yield of 80% is obtained; after the dehydrogenation and oxygen reduction treatment, the oxygen content of the 15-53 μm and 45-105 μm niobium-tungsten alloy spherical powder is as low as 120 ppm and 80 ppm respectively. After 3D printing and 1300 DEG C heat treatment of the above powder, the printed product shows excellent comprehensive performance: the density is greater than or equal to 99.5%, the hardness is 235-283 HV, the tensile strength is 400-502 MPa, and the elongation is 18-20.5%. In contrast, if only a single melting method (examples 2-3) is used, the hydrogenation condition deviates from the optimized parameters (examples 4-5), or the plasma side gas ratio is improper (examples 6-9), the powder spherical degree and fine powder yield are significantly reduced, resulting in the corresponding deterioration of the 3D printed product performance; when the dehydrogenation and oxygen reduction treatment is directly carried out without spheroidization step (comparative example 1), the powder spherical degree is only 97.0%, the fine powder yield is reduced to 15.0%, the oxygen content of the printed product is as high as 580 ppm, the density is only 97.5%, and the mechanical properties are significantly reduced (tensile strength 560.3 MPa, elongation 16.2%). The above results fully prove that: the present application realizes the key technical path of preparing high-spherical-degree, low-impurity-content, high-performance niobium-tungsten alloy spherical powder and high-quality 3D printed products through the synergistic control of double melting, accurate hydrogenation, optimized plasma spheroidization and complete dehydrogenation and oxygen reduction process.

Claims

1. A method for producing a niobium-tungsten alloy spherical powder, characterized by, The method comprises the following steps: (1) Ingot melting: niobium (Nb), tungsten (W), molybdenum (Mo) and zirconium (Zr) refractory metal raw materials are weighed according to a preset component ratio, and then melted to obtain a niobium-tungsten alloy ingot with uniform components; (2) Hydrogenation crushing: the niobium-tungsten alloy ingot obtained in step (1) is placed in a hydrogenation tank for hydrogenation treatment; after the hydrogenation treatment, mechanical crushing is performed to obtain a niobium-tungsten alloy hydride powder; (3) Plasma spheroidization: the niobium-tungsten alloy hydride powder obtained in step (2) is subjected to plasma spheroidization treatment to obtain a niobium-tungsten alloy spherical powder; (4) Dehydrogenation treatment: the spheroidized niobium-tungsten alloy spherical powder is subjected to dehydrogenation treatment at a temperature of 450-750°C for 1-3 hours; (5) Oxygen reduction treatment: magnesium powder is added to the dehydrogenated niobium-tungsten alloy powder, and the mixture is treated in an inert gas at a temperature of 800-1100°C for 2-5 hours to obtain a low-oxygen niobium-tungsten alloy spherical powder.

2. The method of claim 1, wherein the Nb-W alloy spherical powder is prepared by the steps of: preparing a Nb-W alloy ingot; melting the Nb-W alloy ingot; and performing a powdering process on the melted Nb-W alloy ingot. In step (1), the refractory metal raw materials have a mass percentage of 4.5-6.6% tungsten, 1.6-2.8% molybdenum, 0.7-1.6% zirconium, and the balance being niobium. The weighed refractory metal raw material is loaded into a vacuum electromagnetic induction levitation melting furnace, vacuumed to below 2.0*10 - 3 The uniform composition ingot is obtained by repeatedly melting at least 5 times, with each time not less than 25 min, under the protection of argon gas, and then by vacuum electron beam melting at a temperature not higher than 3000 DEG C, a power of 550-650 kW, a speed of 80-150 kg / h, and each time not less than 30 min.

3. The method of claim 1, wherein the Nb-W alloy spherical powder is prepared by the steps of: preparing a Nb-W alloy ingot; melting the Nb-W alloy ingot; and performing a powdering process on the melted Nb-W alloy ingot. In step (2), the hydrogenation tank is first vacuumed to a vacuum degree of not higher than 5x10 -2 Pa, then hydrogen is filled in, the temperature of the hydrogenation process is controlled at 800-1000℃, the hydrogenation time is set to 1-3h, and the hydrogen pressure is maintained at 0.05-0.15MPa. After the hydrogenation crushing, the hydrogen content in the niobium-tungsten alloy hydride powder is 0.1%-1.0%, and the particle size of the niobium-tungsten alloy hydride powder is 150-300 mesh.

4. The method of claim 3, wherein the Nb-W alloy spherical powder is prepared by the steps of: preparing a Nb-W alloy ingot; melting the Nb-W alloy ingot; and performing a powdering process on the melted Nb-W alloy ingot. In step (3), the plasma side gas is argon, or a mixture of helium and argon, or a mixture of hydrogen and argon; the flow rate of the plasma side gas is 40-75 L / min.

5. The method of claim 4, wherein the Nb-W alloy spherical powder is prepared by the steps of: preparing a Nb-W alloy ingot; melting the Nb-W alloy ingot; and performing a centrifugal casting process on the melted Nb-W alloy ingot. The side gas is a mixture of hydrogen and argon, and the molar ratio of hydrogen to argon is 0.03-0.07:1, so that the niobium-tungsten alloy hydride powder undergoes hydrogen explosion during spheroidization to obtain a fine powder yield of the niobium-tungsten alloy spherical powder of 70%-80%.

6. The method of claim 1, wherein the Nb-W alloy spherical powder is prepared by the steps of: preparing a Nb-W alloy ingot; melting the Nb-W alloy ingot; and performing a powdering process on the melted Nb-W alloy ingot. In step (3), the particle size distribution of the niobium-tungsten alloy spherical powder includes two ranges of 15-53 μm and 45-105 μm, and the sphericity of the powder is ≥95%; The powder with a particle size of 15-53 μm is obtained by adjusting the spheroidization process parameters to make the powder undergo hydrogen explosion during the spheroidization treatment in step (3), and then screening the powder; The powder with a particle size of 45-105 μm is obtained by shrinking the hydride powder during the spheroidization treatment in step (3).

7. The method of claim 1, wherein the Nb-W alloy spherical powder is prepared by the steps of: preparing a Nb-W alloy ingot; melting the Nb-W alloy ingot; and performing a powdering process on the melted Nb-W alloy ingot. In step (3), the temperature of the plasma spheroidization treatment is 8000-12000°C, and the reaction pressure is 0.01-0.15 MPa.

8. A 3D printing method using the Nb-W alloy spherical powder prepared by the method according to any one of claims 1 to 7, wherein the Nb-W alloy spherical powder is used. The method comprises the following steps: (1) 3D printing forming: a low-oxygen niobium-tungsten alloy spherical powder is formed into a niobium-tungsten alloy printed product by laser selective melting forming and electron beam selective melting forming; (2) Heat treatment: the printed niobium-tungsten alloy printed product is subjected to heat treatment.

9. The 3D printing method according to claim 8, characterized in that, In step (1), the power of the laser selective melting forming is 120-540 W, the scanning speed is 350-1000 mm / s, the laser strip spacing is 0.05-0.1 mm, and the powder laying thickness is 20-40 µm; The preheating temperature of the electron beam selective melting forming substrate is 600-900 ℃, the beam current is 5-15 mA, the scanning speed is 250-750 mm / s, the melting interval is 0.05-0.2 mm, and the layer thickness is 25-55 µm.

10. The 3D printing method of claim 8, wherein, In step (2), the temperature of the heat treatment is 600-1300 ℃, and the holding time is 1-10 h.

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