Tantalum-tungsten alloy spherical powder, method for preparing same, and additive manufacturing method

Abstract

This invention discloses a spherical powder of tantalum-tungsten alloy and its preparation method and additive manufacturing method, belonging to the field of refractory metal material preparation technology. The preparation method includes: subjecting a homogeneous tantalum-tungsten alloy ingot to a three-stage hydrogenation treatment, sequentially holding at 0.01~0.04 MPa and 300~500℃ for 1~3 h, at 0.04~0.08 MPa and 900~1000℃ for 0.5~1 h, and at 0.02~0.05 MPa and 300~400℃ for 0.5~1.5 h. This segmented hydrogenation process controls the diffusion behavior of hydrogen in the alloy, achieving controlled embrittlement and avoiding over-hydrogenation. Further, multi-cycle crushing and dynamic sieving based on the target particle size range are performed to obtain hydride precursor powder, significantly reducing ineffective fine powder and improving the yield and production efficiency of the plasma spheroidization process. The resulting tantalum-tungsten alloy spherical powder has a sphericity of not less than 99%, an oxygen content of not more than 150 ppm, and a concentrated particle size distribution. It is suitable for additive manufacturing processes such as laser selective melting and electron beam selective melting, providing a reliable raw material for the forming of high-performance tantalum-tungsten alloy components.

Description

Technical Field

[0001] This invention relates to the field of refractory metal material preparation technology, and in particular to a tantalum-tungsten alloy spherical powder and its preparation method and additive manufacturing method. Background Technology

[0002] Tantalum-tungsten alloy (Ta-W alloy) has become a key material system for high-end equipment and extreme working conditions due to its unique comprehensive physicochemical properties, including high melting point, excellent high-temperature strength, corrosion resistance, and creep resistance. This alloy can withstand the harsh service conditions of long-term high temperature, strong radiation, and corrosive media, thus possessing irreplaceable engineering application value in fields such as hot-end components of aerospace engines and high-temperature load-bearing components in the nuclear industry.

[0003] However, tantalum-tungsten alloy powders compatible with powder bed fusion additive manufacturing technology need to possess high sphericity, narrow particle size distribution, high bulk density, and good flowability, while maintaining a low oxygen content to ensure uniform powder spreading, stable molten pool, and effective suppression of defects such as porosity and incomplete fusion. Currently, the main preparation methods for tantalum-tungsten alloy powders include mechanical grinding and gas atomization. Powders obtained by mechanical grinding are often irregular in shape and have rough surfaces, and their sphericity and flowability are difficult to meet the requirements for high-quality powder spreading. For high-melting-point tantalum-tungsten alloys, the gas atomization process faces problems such as melting difficulties, poor sphericity control, and the easy formation of satellite balls and inclusions, resulting in common porosity and incomplete fusion defects in the formed parts, which seriously affect their density and mechanical properties. In addition, existing powder preparation processes also suffer from low yields, especially during the gas atomization process. Due to phenomena such as fine powder scattering, wall adhesion, and satellite ball formation, the yield of spherical powders that meet the requirements of additive manufacturing is usually low, which not only increases raw material costs but also restricts the ability to supply powders on a large scale and with stability.

[0004] Furthermore, tantalum-tungsten alloy powders with different tungsten content ratios and particle sizes are highly sensitive to energy input parameters during selective laser melting (SLM) and selective electron beam melting (SEBM) printing. Uniform laser or electron beam parameters are often incompatible with powders of different composition ratios or particle sizes, leading to fluctuations in the density, microstructure uniformity, mechanical properties, and high-temperature performance of the formed parts. This severely restricts the stable forming quality and mass production capability of tantalum-tungsten alloy additive manufacturing components.

[0005] Therefore, developing a method for preparing tantalum-tungsten alloy spherical powders with high sphericity, high flowability, low oxygen content, uniform composition, and high yield, as well as an additive manufacturing parameter system that matches powders with different content ratios and particle sizes, has significant engineering value and application prospects. Summary of the Invention

[0006] This invention addresses the problems of over-hydrogenation and difficulty in controlling particle size during fragmentation caused by the strong affinity and high diffusivity of tantalum for hydrogen in tantalum-tungsten alloys. It employs a segmented hydrogenation process to precisely control hydrogen diffusion and embrittlement, achieving controlled embrittlement of the alloy and avoiding overall over-hydrogenation. Furthermore, a synergistic process of graded crushing and dynamic sieving based on the target particle size range ensures timely separation of powder reaching the target particle size, effectively suppressing over-crushing and reducing the generation of ineffective ultrafine powder. This results in high-quality precursor powder with concentrated particle size, suitable for plasma spheroidization, improving the yield of spherical powder at the target particle size and overall production efficiency. The prepared tantalum-tungsten alloy spherical powder exhibits high sphericity (≥99%), low oxygen content (≤150 ppm), and concentrated particle size distribution, meeting the raw material requirements of various powder bed melting processes such as laser selective melting and electron beam selective melting. This provides a reliable material guarantee for the additive manufacturing of high-performance, dense tantalum-tungsten alloy components.

[0007] The technical solution provided by this invention is as follows:

[0008] In a first aspect, the present invention provides a method for preparing tantalum-tungsten alloy spherical powder, comprising the following steps:

[0009] (1) Raw material preparation and smelting: Tantalum and tungsten metal raw materials are mixed in a preset ratio, and then vacuum degassing and electron beam smelting are performed to obtain tantalum-tungsten alloy ingots with uniform composition.

[0010] (2) Hydrogenation and crushing treatment: The ingot is subjected to segmented hydrogenation treatment, which includes the following steps:

[0011] a) Keep warm at 0.01~0.04 MPa and 300~500℃ for 1~3 h;

[0012] b) Hold at 0.04~0.08 MPa and 900~1000℃ for 0.5~1 h;

[0013] c) Incubate at 0.02~0.05 MPa and 300~400℃ for 0.5~1.5 h;

[0014] Subsequently, based on the particle size requirements of the end product, the hydrogenated and embrittled alloy was mechanically crushed and sieved to obtain tantalum-tungsten alloy hydride precursor powder with a hydrogen content of 0.8~1.0 wt%.

[0015] (3) Plasma spheroidization treatment: The precursor powder is subjected to radio frequency plasma spheroidization to obtain tantalum-tungsten alloy spherical powder in the target particle size range;

[0016] (4) Dehydrogenation and oxygen reduction treatment: The spherical powder is subjected to integrated dehydrogenation and magnesium thermal reduction treatment, and the process parameters are set according to the target particle size range of the powder.

[0017] In one specific implementation, the preset proportion of ingredients is: 2.5~15 wt% tungsten content, with the balance being tantalum.

[0018] In one specific implementation, in step (2), the process parameters for mechanical crushing are set according to the target particle size range, specifically as follows:

[0019] When the target particle size range is 45~105 μm, the mechanical crushing cycle is 1~3 times, and the single crushing time is 2~3 min;

[0020] When the target particle size range is 15~53 μm, the mechanical crushing cycle is 4~6 times, and the single crushing time is 2~5 min;

[0021] When the target particle size range is 5~25 μm, the mechanical crushing cycle is 7~10 times and the single crushing time is 3~6 min.

[0022] In one specific implementation, in step (2), the yield of the precursor powder in the target particle size range is 70-85%. After removing unsuitable powder with a particle size <5 μm by sieving, the total yield of powder (including the target particle size range and other applicable ranges) that meets the additive manufacturing requirements is ≥90%.

[0023] In one specific implementation, in step (3), the process parameters for radio frequency plasma spheroidization are as follows: plasma power 30~100 kW; central gas is argon with a flow rate of 15~40 L / min; side gas is a mixture of argon, helium and hydrogen, wherein the argon flow rate is 45~100 L / min, the helium flow rate is 20~40 L / min, and the hydrogen flow rate is 0.5~3.5 L / min; powder carrier gas is argon with a flow rate of 3~6 L / min; powder feeding rate is 30~60 g / min; and reaction chamber pressure is 10~17 psi.

[0024] In one specific implementation, step (4) includes the integrated dehydrogenation and magnesium thermal reduction oxygen reduction treatment: mixing the tantalum-tungsten alloy spherical powder with magnesium powder, and performing a three-stage heating treatment under alternating control of inert atmosphere and vacuum conditions, specifically: the first stage: evacuating to a vacuum degree ≤ 5×10 -3 Pa, purging argon gas to 0.1~0.2 MPa, processing temperature 400~490℃, holding at the temperature for 0.5~1 h;

[0025] The second stage involves setting the temperature and holding time based on the target particle size range, specifically as follows:

[0026] When the target particle size range is 45~105 μm, the processing temperature is 1000~1090℃, and the holding time is 3.5~5 h;

[0027] When the target particle size range is 15~53 μm, the processing temperature is 900~990℃, and the holding time is 2.5~4 h;

[0028] When the target particle size range is 5~25 μm, the processing temperature is 800~890℃, and the holding time is 2~3 h;

[0029] Third stage: While maintaining the processing temperature of the second stage, evacuate to a vacuum level ≤5×10⁻⁶. -3 Pa, the holding time is set according to the target particle size range, specifically as follows:

[0030] When the target particle size range is 45~105 μm, keep warm for 2~3 h;

[0031] When the target particle size range is 15~53 μm, keep warm for 1.5~2.5 h;

[0032] When the target particle size range is 5~25 μm, keep warm for 1~1.5 h.

[0033] The added magnesium powder is 0.1~0.5 wt% of the mass of the tantalum-tungsten alloy spherical powder.

[0034] After the third stage of heat preservation is completed, a vacuum is drawn until the vacuum degree is ≤5×10. -3 Pa, introduce argon gas to 0.1~0.2 MPa, and cool to room temperature.

[0035] In one specific implementation, after step (4), the following post-processing steps are also included:

[0036] (5) Passivation treatment: Evacuate to a vacuum degree ≤ 5×10 -3 Pa, argon gas and a mixture of argon and oxygen gas are introduced to carry out at least four stages of passivation cycle, with the oxygen concentration in each stage controlled successively at 1%~3%, 5%~8%, 12%~17% and 22%~26%, and each stage lasting 15~60 min;

[0037] (6) Pickling treatment: The passivated powder is washed with a hydrochloric acid solution with a concentration of 15%~30%.

[0038] Secondly, the present invention also provides a tantalum-tungsten alloy spherical powder, which is prepared by the method described in any of the above-mentioned methods, wherein the sphericity of the powder is ≥99%, the oxygen content is ≤150 ppm, and the yield of the final target particle size range after acid washing is 60%~78%.

[0039] Thirdly, the present invention also provides an additive manufacturing method for tantalum-tungsten alloy components, using the aforementioned tantalum-tungsten alloy spherical powder as raw material, and selecting a corresponding powder bed melting process for forming according to the particle size range of the powder:

[0040] When the particle size range of the powder is 5~25 μm or 15~53 μm, laser selective melting process is adopted.

[0041] When the particle size of the powder is in the range of 45~105 μm, electron beam selective melting process is adopted.

[0042] In one specific implementation, the parameters of the laser selective melting process are: laser power 150~400 W, scanning speed 200~800 mm / s, scanning spacing 70~150 μm, and powder layer thickness 20~40 μm;

[0043] The parameters of the electron beam selective melting process are as follows: substrate preheating temperature 700~1000℃, beam current 10~25 mA, scanning speed 400~1000 mm / s, scanning spacing 50~200 μm, and powder layer thickness 40~80 μm.

[0044] In one specific embodiment, a heat treatment step is further included after forming, wherein the heat treatment temperature is 1000~1400℃ and the holding time is 60~180 min.

[0045] By adopting the above technical solution, the tantalum-tungsten alloy spherical powder and its preparation method and additive manufacturing method provided by the present invention have the following beneficial effects:

[0046] 1. This invention employs a segmented hydrogenation process to precisely control the adsorption, diffusion, and embrittlement behavior of hydrogen in tantalum-tungsten alloys, enabling the alloy to achieve controllable, uniform, and moderate embrittlement, effectively avoiding overall excessive embrittlement caused by uncontrolled hydrogenation. Furthermore, by combining a multi-cycle controllable crushing and dynamic sieving process based on the target particle size range, it is possible to specifically prepare alloys concentrated in the 5... 25 μm, 15 53 μm or 45 Hydride precursor powders with specific particle sizes such as 105 μm significantly reduce the ineffective ultrafine powder generated by excessive crushing, thereby significantly improving the target particle size yield of precursor powder and overall process efficiency.

[0047] 2. This invention introduces a small amount of hydrogen gas during the radio frequency plasma spheroidization process, which is excited into highly reactive hydrogen atoms in the high-temperature plasma. On the one hand, the release of hydrogen atoms in the tantalum matrix induces the formation of a large number of lattice defects, providing migration channels for tungsten atoms with weak diffusion capabilities, thereby achieving further homogenization of the alloy composition. On the other hand, the highly reactive hydrogen atoms react with low-melting-point elemental impurities such as iron, nickel, and silicon, as well as gaseous elemental impurities such as carbon and nitrogen, at high temperatures to generate volatile compounds, or promote the direct evaporation of the above impurities in the high-temperature plasma, allowing the impurities to escape with the gas flow, thereby achieving simultaneous purification of the powder during the spheroidization process.

[0048] 3. This invention addresses the different dehydrogenation and oxygen reduction thermodynamic behaviors of tantalum-tungsten alloy spherical powders with varying specific surface areas due to their different particle sizes. It employs a segmented dehydrogenation and oxygen reduction process, matching differentiated temperatures to powders of different particle sizes. The time parameter ensures that hydrogen and oxygen impurities are fully removed, while effectively preventing fine powder from sintering and agglomerating due to excessively high process temperature and time, and preventing coarse powder from failing to dehydrogenate and reduce oxygen due to insufficient process temperature and time.

[0049] 4. This invention addresses the problem of rapid oxygen absorption and localized over-oxidation in tantalum-tungsten alloy spherical powders due to their high activity. It employs a passivation process with progressively increasing oxygen concentration to gradually form a uniform, dense, and stable ultra-thin passivation oxide layer on the powder surface. This effectively controls the surface oxidation reaction, avoiding uneven powder performance caused by sudden changes in oxygen concentration, thereby significantly reducing the oxidation risk of the powder during subsequent storage, transportation, and use.

[0050] 5. This invention addresses the residual metallic magnesium and its oxides on the surface of powder after magnesium thermal reduction by employing a single-concentration hydrochloric acid solution for pickling. This process exhibits extremely low corrosivity to the tantalum-tungsten alloy matrix, effectively removing surface residues while avoiding excessive erosion, material loss, and reduced yield caused by using highly corrosive media such as hydrofluoric acid on fine-particle powders. Furthermore, the waste liquid from this pickling process has a simple composition, simplifies post-treatment, and offers high environmental controllability.

[0051] 6. The powder preparation method provided by the present invention can prepare low-oxygen tantalum-tungsten alloy spherical powders with different component ratios and different particle size ranges, wherein the powder sphericity is ≥99%, the oxygen content is ≤150ppm, the yield of the final target particle size range after acid washing is 60%~78%, the particle size distribution is concentrated, and it fully meets the requirements of additive manufacturing for powder quality.

[0052] 7. The additive manufacturing process for adapting low-oxygen tantalum-tungsten alloy spherical powder provided by the present invention can select SLM or SEBM process according to the particle size range. Furthermore, the process parameters can be adjusted according to the composition ratio to form products with excellent density and mechanical properties. Attached Figure Description

[0053] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0054] Figure 1 This is an enlarged photograph of the spherical tantalum-tungsten alloy powder of Embodiment 1 of the present invention;

[0055] Figure 2 This is an enlarged photograph of the spherical tantalum-tungsten alloy powder of Embodiment 2 of the present invention;

[0056] Figure 3 This is an enlarged photograph of the spherical tantalum-tungsten alloy powder of Example 3 of the present invention;

[0057] Figure 4 This is an enlarged photograph of the spherical tantalum-tungsten alloy powder of Example 4 of the present invention;

[0058] Figure 5 This is an enlarged photograph of the spherical tantalum-tungsten alloy powder of Example 5 of the present invention;

[0059] Figure 6 A photograph of the spherical tantalum-tungsten alloy product of Embodiment 10 of the present invention;

[0060] Figure 7 This is a photograph of the spherical tantalum-tungsten alloy product of Embodiment 13 of the present invention. Detailed Implementation

[0061] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0062] The term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of this application. In the description of this application, it should be understood that the terms "upper," "lower," "top," "bottom," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein.

[0063] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included. For example, a specified range from “1 to 10” should be considered to include any and all subranges between the minimum value 1 and the maximum value 10. Exemplary subranges of the range 1 to 10 include, but are not limited to, 1 to 6.1, 3.5 to 7.8, 5.5 to 10, etc.

[0064] In existing tantalum-tungsten alloy powder preparation processes, the typical sequence is "hydrogenation crushing treatment → dehydrogenation and oxygen reduction treatment → plasma spheroidization treatment." However, this process has several shortcomings in actual production: First, the powder surface after dehydrogenation and oxygen reduction is in a highly active, low-oxygen state. During transfer, temporary storage, and spheroidization feeding, it is inevitably exposed to an oxygen-rich environment, making secondary oxygen absorption likely. Second, the raw material powder undergoing plasma spheroidization is already dehydrogenated, and hydrogen-induced explosions are virtually nonexistent during spheroidization. Therefore, the particle size of the raw material powder must be strictly controlled within the target particle size range, placing high demands on raw material sieving and classification, resulting in reduced raw material utilization and insufficient process flexibility. Third, since the raw material powder has already undergone dehydrogenation, hydrogen cannot be introduced as a side gas during the spheroidization stage; only a mixture of argon and helium can be used, increasing production costs. Fourth, the spheroidization process inevitably produces a certain proportion of ultrafine or nanoscale powders, which typically require cleaning and drying to separate the micro-nano composite powders. However, the aforementioned cleaning and drying processes easily cause irreversible oxygenation, weakening the effectiveness of the preceding dehydrogenation and oxygen reduction processes.

[0065] To address the aforementioned shortcomings, this invention employs an innovative process design based on the synergistic spheroidization and refined dehydrogenation / oxygenation of hydrogen-containing precursor powders. After hydrogenation and crushing, plasma spheroidization is performed first, followed by dehydrogenation / oxygenation. After hydrogenation and crushing, the precursor powder remains hydrogen-containing, and its surface chemical activity is relatively controlled. Under the high-temperature environment of plasma spheroidization, hydrogen helps promote compositional homogenization and reduce impurity content. Simultaneously, hydrogen-containing powders can undergo a hydrogen explosion reaction during spheroidization, transforming coarse particles into the target particle size range. This allows for the use of precursor powders with a wider particle size range for spheroidization, reducing the initial constraints on raw material particle size and improving raw material adaptability and overall yield. After plasma spheroidization and obtaining tantalum-tungsten alloy spherical powders with regular morphology and concentrated particle size distribution, dehydrogenation / oxygenation treatment is then performed for different particle size ranges. At this point, the powder surface is uniform and stable, facilitating precise control of hydrogen release and oxygen removal, and preventing secondary oxygen absorption. This process design not only significantly reduces the oxygen content of the final powder and improves the consistency of composition and performance, but also makes it more suitable for high-end applications such as additive manufacturing.

[0066] This invention further addresses the strong affinity and high diffusivity of tantalum for hydrogen in tantalum-tungsten alloys. It points out that traditional one-time high-temperature, high-pressure hydrogenation treatment easily leads to over-hydrogenation and overall embrittlement of the alloy within a short time, resulting in a large amount of ultrafine powder during subsequent mechanical crushing. This makes it difficult to obtain an ideal particle size precursor suitable for plasma spheroidization, thus affecting the yield of the final target particle size spherical powder. To solve these problems, this invention innovatively adopts a three-stage hydrogenation process in the hydrogenation crushing stage. By segmenting and controlling the diffusion and adsorption of hydrogen in the alloy, controlled embrittlement is achieved, avoiding over-hydrogenation. Furthermore, combined with a multi-cycle crushing and dynamic sieving process based on the target particle size range, the synergistic effect of staged crushing and real-time sieving ensures timely separation of powder reaching the target particle size, effectively suppressing excessive fine powder generation caused by over-crushing. This achieves precise control over the particle size distribution of the precursor powder, providing raw materials with concentrated particle size and controllable morphology for subsequent plasma spheroidization, improving the overall yield and batch stability of spherical powder.

[0067] The following is a method for preparing tantalum-tungsten alloy spherical powder according to an embodiment of the present invention, which specifically includes the following steps:

[0068] (1) Raw material preparation and smelting: First, tantalum (purity ≥ 99.95%) and tungsten (purity ≥ 99.95%) metal raw materials are selected and weighed according to a preset ratio (tungsten content is 2.5~15 wt%, the balance is tantalum). Then, the batched materials are placed in a vacuum electromagnetic induction levitation smelting furnace and evacuated to a vacuum degree ≤ 5×10 -3 The furnace is filled with high-purity argon as a protective atmosphere, and the furnace temperature is maintained at 200~300℃ for 1~2 hours to degas the raw materials to remove surface-adsorbed moisture and gases. After degassing, the raw materials are melted in a vacuum environment using an electron beam. The melting process is repeated at least twice, with each melting temperature in the range of 3200~3400℃ and a holding time of 30~60 minutes to ensure uniform alloy composition and obtain tantalum-tungsten alloy ingots.

[0069] (2) Hydrogenation and Crushing Treatment: Tantalum in tantalum-tungsten alloys has a strong affinity for hydrogen and a high diffusion rate. If one-time high-temperature and high-pressure hydrogenation is used, it is easy to cause rapid over-hydrogenation and overall embrittlement of the tantalum-tungsten alloy, which in turn generates a large amount of uncontrollable fine powder during mechanical crushing. It is difficult to obtain a precursor of the target particle size suitable for plasma spheroidization treatment, which seriously affects the yield of subsequent spherical powder. To this end, the present invention adopts a method combining segmented hydrogenation process with graded crushing-dynamic screening: in the hydrogenation stage, the hydrogen pressure and temperature are controlled stepwise to achieve controllable embrittlement; in the crushing stage, the powder that has reached the target particle size is separated in time to avoid over-crushing due to continuous stress. After hydrogenation treatment and mechanical crushing, tantalum-tungsten alloy hydride precursor powder with concentrated particle size distribution and hydrogen content of 0.8~1.0 wt% is obtained.

[0070] The specific hydrogenation steps are as follows:

[0071] The tantalum-tungsten alloy ingot is placed in a hydrogenation device and evacuated to a vacuum level of ≤ 5×10⁻⁶. -3The alloy is charged with hydrogen gas and subjected to a three-stage hydrogenation process: First, it is held at a hydrogen pressure of 0.01–0.04 MPa and a temperature of 300–500 °C for 1–3 h. During this stage, hydrogen mainly adsorbs and initially diffuses at the alloy surface and grain boundaries, forming initial grain boundary weakening zones and surface defects, providing channels for subsequent hydrogen diffusion, but without causing significant overall embrittlement. Next, the hydrogen pressure is increased to 0.04–0.08 MPa and the temperature to 900–1000 °C, and held for 0.5–1 h. During this stage, hydrogen diffuses rapidly along the formed weakening zones and surface defects, promoting crack propagation along grain boundaries and defects, achieving uniform embrittlement of the alloy. At the same time, by significantly shortening the holding time, the full bulk diffusion and dissolution of hydrogen within the grains is suppressed, fundamentally avoiding excessive and uncontrolled embrittlement. Finally, the hydrogen pressure is reduced to 0.02~0.05 MPa, heating is stopped, and the temperature is lowered to 300~400 ℃, held for 0.5~1.5 h. This stage stabilizes the hydrogen-induced cracks that have already formed, preventing the hydrogen introduced in the high-temperature stage from redistributing or escaping during cooling, which could lead to stress concentration. This ensures the uniformity and controllability of the hydrogenated structure, providing an ideal brittle microstructure for subsequent fracture. Hydrogen pressure, hydrogenation temperature, and holding time are key process parameters that work together to determine the dissolution and diffusion behavior of hydrogen in tantalum-tungsten alloys. When the hydrogen pressure, hydrogenation temperature, or holding time is too high, excessive hydrogen dissolves in the tantalum matrix, leading to uncontrolled embrittlement. This results in overall pulverization during subsequent crushing, producing a large amount of uncontrollable ultrafine powder with severely dispersed particle size distribution, significantly reducing the yield within the target particle size range. Conversely, when the hydrogen pressure, hydrogenation temperature, or holding time is too low, hydrogen adsorption and diffusion in the alloy are limited, and hydrogenation is mainly confined to the alloy surface, resulting in insufficient overall embrittlement. This leads to reduced subsequent crushing efficiency, requiring more crushing cycles or longer crushing times, increasing the difficulty of controlling powder particle size, and hindering the acquisition of precursor powder with controllable particle size. After the above-mentioned segmented hydrogenation treatment, the alloy forms a uniform and controllable brittle structure, facilitating the subsequent acquisition of precursor powder with concentrated particle size suitable for plasma spheroidization through graded crushing and dynamic sieving.

[0072] Subsequently, the hydrogenated tantalum-tungsten alloy was subjected to impact crushing. After each crushing cycle, powder from multiple particle size ranges was simultaneously collected and sorted using sieves of different mesh sizes. The undersize material was collected directly as the product of the corresponding particle size range, while the oversize material could be returned for further crushing as needed. The number of crushing cycles was set according to the requirements of the main target particle size range, and the crushing time for each cycle was dynamically adjusted based on the material weight. Through the above multi-cycle mechanical crushing and post-cycle screening, tantalum-tungsten alloy hydride precursor powder with the target particle size range was finally obtained, with a yield of 70%–85% for the target particle size range.

[0073] (3) Plasma spheroidization treatment: The tantalum-tungsten alloy hydride precursor powder with a specific particle size distribution obtained in step (2) is fed into a radio frequency plasma device as raw material. Under an inert atmosphere, the powder is rapidly melted and spheroidized using the high temperature and high enthalpy region generated by the radio frequency plasma. The powder particles melt instantly when passing through the plasma torch, forming spherical droplets under the action of surface tension, and then solidify during rapid cooling, thereby obtaining tantalum-tungsten alloy spherical powder with high sphericity, high density, and low oxygen content.

[0074] (4) Dehydrogenation and oxygen reduction treatment: The tantalum-tungsten alloy spherical powder is subjected to integrated dehydrogenation treatment and magnesium thermal reduction treatment to remove residual hydrogen in the powder and to significantly reduce the oxygen content of the powder by utilizing the reaction between magnesium and the oxides on the powder surface. Finally, after acid washing, water washing and drying, high-performance tantalum-tungsten alloy spherical powder with low oxygen content, pure chemical composition and good sphericity is obtained.

[0075] In one specific implementation, the preset proportion of the raw materials is: tungsten content 2.5~15 wt%, with the balance being tantalum, such as Ta2.5W, Ta5.5W, Ta7.5W, Ta10W, and Ta15W. Tantalum and tungsten are both high-melting-point metals with similar atomic numbers, atomic radii, and crystal structures. They can be completely dissolved in each component proportion, producing an infinitely miscible substitutional solid solution. Solid solution strengthening improves the room temperature and high-temperature properties of tantalum alloys. Generally, as the tungsten content increases, the alloy grains become finer, and tensile strength, yield strength, and hardness all increase, but ductility and toughness decrease. When the tungsten content is too high, the number of defects in additive manufacturing increases, and the density decreases, failing to meet the performance requirements of engineering applications. Limiting the tungsten content in tantalum-tungsten alloys to 2.5~15 wt% can achieve significant solid solution strengthening and grain refinement while maintaining the complete solid solution properties of the tantalum-tungsten system. At the same time, it avoids the decrease in plasticity and toughness and the increase in additive manufacturing defects caused by excessive tungsten content. This balances the improvement of material properties with the process controllability of powder preparation, plasma spheroidization and additive manufacturing.

[0076] In one specific implementation scheme, in step (2), the hydrogenated tantalum-tungsten alloy is mechanically crushed using an impact crushing method. After each crushing cycle, 140-mesh, 270-mesh, and 500-mesh screens are used to achieve parallel separation and collection of powders across multiple particle size ranges. The undersize material is collected directly, while the oversize material can be returned for further crushing as needed. The number of crushing cycles and the single crushing time are dynamically set based on the target particle size range and material weight.

[0077] When the target particle size range is 45~105 μm, the crushing cycle is 1~3 times, and the single crushing time is 2~3 min. After sieving, powder of 45~105 μm can be obtained as the main product, and by-products of 15~53 μm and 5~25 μm are also produced.

[0078] When the target particle size range is 15~53 μm, the crushing cycle is 4~6 times, and the single crushing time is 2~5 min. After sieving, powder of 15~53 μm can be obtained as the main product, and by-products of 45~105 μm and 5~25 μm are also produced.

[0079] When the target particle size range is 5~25 μm, the crushing cycle is 7~10 times, and the single crushing time is 3~6 min. After sieving, powder of 5~25 μm can be obtained as the main product, and by-products of 45~105 μm and 15~53 μm are also produced.

[0080] The crushing cycle and single crushing time together determine the level of mechanical energy input per unit mass of powder. If the crushing cycle or single crushing time is too long, a large amount of uncontrollable ultrafine powder will be generated, resulting in a dispersed particle size distribution and reduced yield within the target particle size range. Conversely, if the crushing cycle or single crushing time is too short, crushing efficiency will decrease, the proportion of coarse particles remaining will increase, and it will be detrimental to obtaining precursor powder with concentrated particle size suitable for plasma spheroidization. Therefore, different target particle size ranges require matching appropriate crushing cycles and single crushing times to achieve comprehensive optimization of crushing efficiency, particle size concentration, and yield.

[0081] In one specific implementation, during step (3), hydrogen gas is introduced into the edge gas during plasma spheroidization. The hydrogen gas is then dissociated into highly reactive hydrogen atoms under the high-temperature environment of the radio frequency plasma. Hydrogen atoms have small atomic radii and strong diffusion capabilities, allowing them to rapidly dissolve into the tantalum matrix and significantly disrupt lattice stability during subsequent rapid release, thereby inducing a large number of lattice defects. These defects provide effective migration channels for tungsten atoms, which have large atomic radii and weak migration capabilities (their diffusion mechanism mainly relies on vacancy diffusion). Despite the extremely short plasma spheroidization time, tungsten atoms can still diffuse further into the tantalum matrix along the defect channels, promoting the formation of solid solutions and homogenization of composition, which is beneficial for improving the uniformity of the final spherical powder. Furthermore, at high temperatures, hydrogen atoms can react with impurity elements in the tantalum-tungsten alloy: forming low-melting-point compounds with impurities such as iron, nickel, and silicon; generating gaseous compounds with gaseous impurities such as carbon and nitrogen; or promoting the direct evaporation of the impurity elements. These compounds can rapidly volatilize in the high-temperature plasma gas flow or be carried away from the system by the gas flow, thereby significantly reducing the impurity content in the powder.

[0082] The specific process parameters are set as follows: plasma power is 30~100 kW; the central gas is argon, with a flow rate of 15~40 L / min; the peripheral gas is a mixture of argon, helium, and hydrogen, with an argon flow rate of 45~100 L / min, a helium flow rate of 20~40 L / min, and a hydrogen flow rate of 0.5~3.5 L / min; the powder carrier gas is argon, with a flow rate of 3~6 L / min; the powder feeding rate is 30~60 g / min; and the reaction chamber pressure is 10~17 psi. Based on the main particle size range of the precursor powder, after the above spheroidization treatment and sieving, spherical tantalum-tungsten alloy powders corresponding to the main particle size range can be obtained as the main product, and powders of other particle size ranges can be used as by-products. The sphericity of all products is not less than 95%.

[0083] In one specific implementation, due to the significant differences in specific surface area among tantalum-tungsten alloy spherical powders of different particle size ranges, using uniform dehydrogenation or deoxidation process parameters can easily lead to problems such as sintering of fine powder particles or insufficient dehydrogenation and deoxidation of coarse powder particles, affecting the consistency of the final powder quality. Therefore, this process adopts an integrated dehydrogenation and magnesia-thermal reduction deoxidation treatment strategy that combines staged heating with parameter differentiation for different target particle size ranges. By synergistically controlling temperature and holding time, the dehydrogenation and deoxidation processes can be controlled. The integrated dehydrogenation and magnesia-thermal reduction deoxidation treatment includes: first, mixing tantalum-tungsten alloy spherical powder with magnesium powder, and then performing three stages of heating treatment under alternating control of argon atmosphere and vacuum conditions, as detailed below:

[0084] The first stage involves evacuating the vacuum until the vacuum level is ≤5×10⁻⁶. -3 The pressure is increased to 0.1-0.2 MPa by introducing argon gas, and the mixture is kept at 400-490℃ for 0.5-1 h. This stage weakens the tantalum-hydrogen bond energy, promotes the release of weakly bound hydrogen and surface-adsorbed hydrogen, activates oxygen diffusion on the powder surface, and promotes the initial formation of the magnesium-oxygen reaction interface, thus avoiding drastic changes in the powder surface structure caused by a sudden increase in temperature.

[0085] The second stage involves high-temperature treatment under an argon atmosphere, with different process parameters set according to the powder particle size range. Large-particle powders (e.g., 45~105 μm) have a small specific surface area and longer diffusion paths for hydrogen and oxygen, requiring higher temperatures and longer holding times to ensure complete removal of internal hydrogen and oxygen. Small-particle powders (e.g., 5~25 μm) have a large specific surface area and high reactivity, with shorter diffusion paths for hydrogen and oxygen, but prolonged high-temperature treatment can easily lead to sintering or agglomeration; therefore, the temperature and time need to be appropriately reduced. The specific process settings are as follows:

[0086] When the target particle size range is 45~105 μm, the processing temperature is 1000~1090℃, and the holding time is 3.5~5 h;

[0087] When the target particle size range is 15~53 μm, the processing temperature is 900~990℃, and the holding time is 2.5~4 h;

[0088] When the target particle size range is 5~25 μm, the processing temperature is 800~890℃, and the temperature is maintained for 2~3 h.

[0089] In the third stage, while maintaining the processing temperature of the second stage, a vacuum is evacuated until the vacuum level is ≤5×10⁻⁶. -3 Pa, and continue to hold at the target particle size range to promote further hydrogen escape from the powder interior in a low partial pressure, high temperature environment, and to drive the completion of the magnesian thermal reduction reaction, thereby achieving deep dehydrogenation and stable oxygen reduction. Setting the holding time according to the powder particle size range can effectively control the sintering risk while ensuring the consistency and stability of powder batch purity. The specific process settings are as follows:

[0090] When the target particle size range is 45~105 μm, keep warm for 2~3 h;

[0091] When the target particle size range is 15~53 μm, keep warm for 1.5~2.5 h;

[0092] When the target particle size range is 5~25 μm, keep warm for 1~1.5 h.

[0093] The added magnesium powder accounts for 0.1-0.5% of the mass of the tantalum-tungsten alloy spherical powder. Magnesium is a strong reducing agent that reacts with residual oxygen on and inside the tantalum-tungsten alloy powder to form magnesium oxide (MgO). If the magnesium powder mass is too high, it may cause localized overheating of the powder surface, leading to particle sintering or agglomeration and the production of a large amount of magnesium oxide. This magnesium oxide adheres to the powder surface and is difficult to remove completely, affecting subsequent surface cleanliness and flowability, damaging the powder morphology, and increasing the difficulty of spheroidization. If the magnesium powder mass is too low, there is insufficient reducing agent, making it difficult to fully react with the trace oxygen on the powder surface, failing to meet the low-oxygen requirements, and affecting powder purity and subsequent additive manufacturing performance.

[0094] After the third stage of heat preservation is completed, a vacuum is drawn until the vacuum degree is ≤5×10. -3 Pa, then argon gas is introduced to 0.1~0.2 MPa, and cooled to room temperature to complete the dehydrogenation and deoxygenation process.

[0095] In one specific implementation, after the magnesium thermal reduction deoxygenation treatment, the surface of the resulting tantalum-tungsten alloy spherical powder is in a highly active, low-oxygen state. If directly exposed to air, it is highly susceptible to rapid oxygen absorption and even localized oxidation. Therefore, a gradual passivation process under low-temperature (room temperature) and low-oxygen partial pressure conditions is employed to gradually form a uniform, dense, and extremely thin oxide protective layer on the powder surface. This effectively inhibits oxygen adsorption during subsequent storage and use, ultimately yielding tantalum-tungsten alloy spherical powder with low hydrogen content, stable oxygen content, and high safety.

[0096] The specific passivation process is as follows: First, the equipment is evacuated to a vacuum level ≤ 5 × 10⁻⁶. -3 Pa was then introduced, followed by the introduction of argon and a mixture of argon and oxygen (initial oxygen-argon volume ratio 1:1). By adjusting the flow rates of the two gases in stages, the oxygen content within the equipment was gradually increased to four gradients: 1-3%, 5-8%, 12-17%, and 22-26%. Each oxygen content gradient was maintained for 15-60 minutes, completing one passivation cycle, ultimately achieving stable and controllable oxidation protection of the powder surface. This multi-step progressive passivation method can form a uniform and well-bonded oxide layer on the powder surface at room temperature, avoiding powder performance changes that may be caused by high-temperature processing, and ensuring the chemical stability of the final powder during long-term storage and subsequent processing.

[0097] In one specific implementation, after dehydrogenation, deoxygenation, and passivation treatments, a small amount of unreacted magnesium powder and its reaction product, magnesium oxide, inevitably remain on the surface of the tantalum-tungsten alloy spherical powder. If not removed, these residues will affect the surface cleanliness, flow properties, and forming quality of the powder in subsequent additive manufacturing processes. Therefore, the treated powder is placed in a corrosion-resistant container, and a 15-30% hydrochloric acid solution is added, followed by stirring and washing at room temperature. Through this step, the residual magnesium powder and magnesium oxide react fully with the hydrochloric acid to generate soluble magnesium chloride, which is then discharged with the acid solution. Subsequently, the powder is rinsed multiple times with deionized water until the washing solution is neutral. After drying, a low-oxygen tantalum-tungsten alloy spherical powder with a clean surface and a stable oxygen content controlled at ≤150 ppm is finally obtained. Compared with existing technologies that use mixed pickling processes containing hydrofluoric acid, nitric acid, and hydrochloric acid, the single hydrochloric acid pickling process used in this invention has the following advantages: First, hydrochloric acid can efficiently dissolve the metallic magnesium and its oxides remaining after the thermal reduction of magnesium, while having virtually no corrosion on the tantalum-tungsten alloy substrate and surface passivation layer. This achieves selective removal of target impurities, avoiding mass loss and yield reduction caused by the reaction of fine-grained powder with hydrofluoric acid, and also protecting the integrity of the powder surface. Second, this process eliminates the highly corrosive and toxic hydrofluoric acid and nitric acid, reducing operational hazards, environmental emission pressure, and the difficulty of subsequent wastewater treatment. This makes the process safer, more environmentally friendly, and more cost-effective, with greater prospects for industrial application and economic viability.

[0098] This invention also provides a tantalum-tungsten alloy spherical powder, which is prepared by any of the above methods. The powder has a sphericity ≥99%, a smooth surface, good flowability, an oxygen content ≤150 ppm, and a yield of 60%~78% for the final target particle size range. It has low impurity element content and high chemical purity, making it suitable for demanding additive manufacturing and other precision forming processes.

[0099] This invention also provides an additive manufacturing method for tantalum-tungsten alloy components, which uses tantalum-tungsten alloy spherical powder prepared by the above method as raw material, and performs forming according to the powder particle size range matched with a corresponding powder bed melting process:

[0100] When the powder particle size ranges from 5 to 25 μm or 15 to 53 μm, selective laser melting is employed. This process is suitable for fine powders and features a small focused spot, high scanning accuracy, and good surface quality, making it suitable for forming parts with intricate structures and complex features.

[0101] When the powder particle size range is 45~105 μm, electron beam selective melting is used. This process is suitable for coarser powders, is carried out in a vacuum environment, effectively avoids oxidation, and has high electron beam energy density and strong penetration, making it more suitable for forming components with large size and high density requirements.

[0102] In one specific implementation, tantalum-tungsten alloys, with their high melting point and high density, require high energy density to ensure complete melting. Based on extensive experimental research on pure tantalum SLM and SEBM processes, and considering the influence of tungsten content (2.5–15 wt%) on alloy properties, the inventors optimized the additive manufacturing process parameters for tantalum-tungsten alloys. Specifically, the parameters for laser selective melting (SLM) are: laser power 150–400 W, scanning speed 200–800 mm / s, scanning distance 70–150 μm, and powder layer thickness 20–40 μm; the parameters for electron beam selective melting (EBM) are: substrate preheating temperature 700–1000 °C, beam current 10–25 mA, scanning speed 400–1000 mm / s, scanning distance 50–200 μm, and powder layer thickness 40–80 μm. In the SLM process, these parameter settings ensure sufficient energy input to melt the high-melting-point powder without localized overheating or spattering, reducing porosity or crack formation and resulting in a highly dense formed part. In the SEBM process, it is ensured that the powder with a high layer thickness is fully melted at high temperature, the formed parts are dense and uniform, and the risk of thermal stress and warping deformation is effectively reduced.

[0103] In one specific implementation, a heat treatment step is included after forming. The heat treatment temperature is 1000~1400℃, and the holding time is 60~180 min. This eliminates residual stress generated during forming, promotes the homogenization and stabilization of the microstructure, and improves the dimensional stability and overall density of the formed part.

[0104] The following detailed description of examples of the present invention is exemplary and is used only to explain the present invention, and should not be construed as limiting the present invention.

[0105] Example 1

[0106] A method for preparing tantalum-tungsten alloy spherical powder includes the following steps:

[0107] (1) Raw material preparation and smelting: Weigh tantalum (purity ≥99.95%) and tungsten (purity ≥99.95%) metal raw materials according to the mass percentage of Ta:W=97.5:2.5, place them in a vacuum electromagnetic induction levitation smelting furnace, and evacuate to 5.0×10 -3 The mixture was protected with argon gas and held at 200℃ for 1 hour; subsequently, it was melted twice by vacuum electron beam at 3200℃ for 30 minutes to obtain a tantalum-tungsten alloy (Ta2.5W) ingot with uniform composition. Its chemical composition is shown in Table 1.

[0108] Table 1

[0109]

[0110] (2) Hydrogenation and crushing treatment: The tantalum-tungsten alloy ingot is placed in the hydrogenation equipment and vacuumed to 5×10 -3 After passing through a pressure of 0.03 MPa, hydrogen gas is introduced, and a three-stage hydrogenation process is performed. The first stage involves heating to 500℃ and holding for 2 hours at a hydrogen pressure of 0.03 MPa. The second stage involves increasing the hydrogen pressure to 0.06 MPa and heating to 1000℃ and holding for 0.5 hours. The third stage involves adjusting the hydrogen pressure back to 0.03 MPa and cooling to 400℃ and holding for 1 hour. The hydrogenated alloy is then mechanically crushed through four crushing cycles, each lasting 5 minutes. The alloy is then graded and sieved using 140-mesh, 270-mesh, and 500-mesh screens to obtain tantalum-tungsten alloy hydride precursor powder with a main particle size range of 15-53 μm, achieving a yield of 78% and a hydrogen content of 0.90%.

[0111] (3) Plasma spheroidization treatment: The tantalum-tungsten alloy hydride precursor powder was subjected to radio frequency plasma spheroidization treatment. The process parameters were as follows: plasma power was 40KW, the central gas was argon (flow rate 19.5L / min), the side gas was a mixture of argon (flow rate 50L / min), helium (flow rate 25L / min) and hydrogen (flow rate 1.0L / min), the powder carrier gas was argon (flow rate 3L / min), the powder feeding rate was 38g / min, and the reaction pressure was 15psi. After sieving, spherical powder of tantalum-tungsten alloy (Ta2.5W) with a particle size range of 15-53μm and a sphericity of 99.5% was obtained.

[0112] (4) Dehydrogenation and oxygen reduction treatment: Add magnesium powder at 0.3wt% of the mass of the spherical tantalum-tungsten alloy powder, mix evenly, place in a degassing device, and evacuate to a vacuum degree of 5×10. -3 Pa, and argon gas was introduced to a pressure of 0.2 MPa. The temperature was first raised to 400℃ and held for 0.5 h. Then, the temperature was raised to 900℃ and held for 4 h. Next, the temperature was maintained at 900℃, and a vacuum was evacuated to a degree of 5 × 10⁻⁶.-3 Pa, heat for 2 hours. After heat treatment, evacuate to a vacuum level of 5 × 10⁻⁶. -3 Pa, then purged with argon gas again to 0.2 MPa, and cooled to room temperature.

[0113] (5) Passivation treatment: Evacuate to a vacuum degree of 5×10 -3 Pa was then introduced, followed by the introduction of argon and a mixture of oxygen and argon (oxygen:argon = 1:1) for four passivation cycles. The process parameters were as follows: First cycle, argon flow rate was 12 L / min, oxygen-argon mixture flow rate was 0.5 L / min, duration was 15 min; Second cycle, argon flow rate was 5.5 L / min, oxygen-argon mixture flow rate was 1 L / min, duration was 20 min; Third cycle, argon flow rate was 3.5 L / min, oxygen-argon mixture flow rate was 1.5 L / min, duration was 30 min; Fourth cycle, argon flow rate was 1.8 L / min, oxygen-argon mixture flow rate was 2 L / min, duration was 30 min.

[0114] (6) Pickling treatment: The passivated tantalum-tungsten alloy powder was washed with 20% hydrochloric acid, followed by repeated rinsing with deionized water until the washing solution was neutral, and then dried. Low-oxygen tantalum-tungsten alloy spherical powder was finally obtained, with a yield of 71%. A magnified photograph of the spherical tantalum-tungsten alloy powder is shown below. Figure 1 The chemical composition is shown in Table 2:

[0115] Table 2

[0116]

[0117] Example 2

[0118] Referring to the preparation method of Example 1, the difference is that in step (1), the mass percentage of tantalum (purity ≥99.95%) and tungsten (purity ≥99.95%) metal raw materials is Ta:W = 94.5:5.5. The chemical composition of the tantalum-tungsten alloy (Ta5.5W) ingot is shown in Table 3:

[0119] Table 3

[0120]

[0121] In step (2), tantalum-tungsten alloy hydride precursor powder with a particle size range of 15~53μm was obtained as the main product, with a yield of 77% and a hydrogen content of 0.91%.

[0122] In step (3), the powder carrier gas is argon (flow rate of 4L / min), and spherical powder of tantalum-tungsten alloy with a particle size range of 15~53μm and a sphericity of 99.2% is obtained by sieving.

[0123] Finally, low-oxygen tantalum-tungsten alloy spherical powder was obtained with a yield of 70%. A magnified photograph of the spherical tantalum-tungsten alloy powder can be found here. Figure 2 The chemical composition is shown in Table 4:

[0124] Table 4

[0125]

[0126] Example 3

[0127] Referring to the preparation method of Example 1, the difference is that in step (1), the mass percentage of tantalum (purity ≥99.95%) and tungsten (purity ≥99.95%) metal raw materials is Ta:W = 90:10. The chemical composition of the tantalum-tungsten alloy (Ta10W) ingot is shown in Table 5:

[0128] Table 5

[0129]

[0130] In step (2), the main particle size range is 5-25μm, the number of crushing cycles is 8, the single crushing time is 6min, and the tantalum-tungsten alloy hydride precursor powder with a particle size range of 5-25μm is obtained as the main product, with a yield of 73% and a hydrogen content of 0.93%.

[0131] In step (3), the side gas is a mixture of argon (flow rate of 52 L / min), helium (flow rate of 27 L / min) and hydrogen (flow rate of 1.0 L / min), and the powder carrier gas is argon (flow rate of 4.8 L / min). After sieving, tantalum-tungsten alloy spherical powder with a particle size range of 5-25 μm and a sphericity of 99.0% is obtained.

[0132] In step (4), magnesium powder is added at 0.5 wt% of the weight of the spherical tantalum-tungsten alloy powder and mixed evenly. The mixture is then placed in a degassing device and evacuated to a vacuum degree of 5 × 10⁻⁶. -3 Pa, and argon gas was introduced to a pressure of 0.2 MPa. The temperature was first raised to 400℃ and held for 0.5 h. Then, the temperature was raised to 800℃ and held for 3 h. Next, the temperature was maintained at 800℃, and a vacuum was evacuated to a degree of 5 × 10⁻⁶. -3 Pa, heat for 1.5 hours. After heat treatment, evacuate to a vacuum level of 5 × 10⁻⁶. -3 Pa, then purged with argon gas again to 0.2 MPa, and cooled to room temperature.

[0133] In step (6), the passivated tantalum-tungsten alloy powder is washed with 30% hydrochloric acid.

[0134] Finally, low-oxygen tantalum-tungsten alloy spherical powder was obtained with a yield of 67%. A magnified photograph of the spherical tantalum-tungsten alloy powder can be found here. Figure 3 The chemical composition is shown in Table 6:

[0135] Table 6

[0136]

[0137] Example 4

[0138] Referring to the preparation method of Example 3, the difference is that in step (2), the main particle size range is 15-53μm, the number of crushing cycles is 4, the single crushing time is 5 min, and the tantalum-tungsten alloy hydride precursor powder with a particle size range of 15-53μm is obtained as the main product, with a yield of 80% and a hydrogen content of 0.93%.

[0139] In step (3), the powder carrier gas is argon (flow rate of 4L / min), and spherical powder of tantalum-tungsten alloy with a particle size range of 15-53μm and a sphericity of 99.6% is obtained by sieving.

[0140] In step (4), magnesium powder is added at 0.3 wt% of the weight of the spherical tantalum-tungsten alloy powder and mixed evenly. The mixture is then placed in a degassing device and evacuated to a vacuum degree of 5 × 10⁻⁶. -3 Pa, and argon gas was introduced to a pressure of 0.2 MPa. The temperature was first raised to 400℃ and held for 0.5 h. Then, the temperature was raised to 900℃ and held for 4 h. Next, the temperature was maintained at 900℃, and a vacuum was evacuated to a degree of 5 × 10⁻⁶. -3 Pa, heat for 2 hours. After heat treatment, evacuate to a vacuum level of 5 × 10⁻⁶. -3 Pa, then purged with argon gas again to 0.2 MPa, and cooled to room temperature.

[0141] In step (6), the passivated tantalum-tungsten alloy powder is washed with 20% hydrochloric acid.

[0142] Finally, low-oxygen tantalum-tungsten alloy spherical powder was obtained with a yield of 72%. A magnified photograph of the spherical tantalum-tungsten alloy powder can be found here. Figure 4 The chemical composition is shown in Table 7:

[0143] Table 7

[0144]

[0145] Example 5

[0146] The preparation method of Example 3 is different in that, in step (2), the main particle size range is 45-105μm, the number of crushing cycles is 2, the single crushing time is 3 min, and the tantalum-tungsten alloy hydride precursor powder with a particle size range of 45-105μm is obtained as the main product, with a yield of 76% and a hydrogen content of 0.95%.

[0147] In step (3), the powder carrier gas is argon (flow rate of 3.5 L / min), and spherical powder of tantalum-tungsten alloy with a particle size range of 45-105 μm and a sphericity of 99.3% is obtained by sieving.

[0148] In step (4), magnesium powder is added at 0.2 wt% of the weight of the spherical tantalum-tungsten alloy powder and mixed evenly. The mixture is then placed in a degassing device and evacuated to a vacuum degree of 5 × 10⁻⁶. -3 Pa, and argon gas was introduced to a pressure of 0.2 MPa. The temperature was first raised to 400℃ and held for 1 hour. Then, the temperature was raised to 1000℃ and held for 5 hours. Next, the temperature was maintained at 1000℃, and a vacuum was evacuated to a degree of 5 × 10⁻⁶. -3 Pa, heat for 3 hours. After heat treatment, evacuate to a vacuum level of 5 × 10⁻⁶. -3 Pa, then purged with argon gas again to 0.2 MPa, and cooled to room temperature.

[0149] In step (6), the passivated tantalum-tungsten alloy powder is washed with 15% hydrochloric acid.

[0150] Finally, low-oxygen tantalum-tungsten alloy spherical powder was obtained with a yield of 68%. A magnified photograph of the spherical tantalum-tungsten alloy powder can be found here. Figure 5 The chemical composition is shown in Table 8:

[0151] Table 8

[0152]

[0153] Example 6

[0154] Referring to the preparation method of Example 1, the difference is that in step (3), the edge gas for plasma spheroidization treatment is only a mixture of argon (flow rate of 50 L / min) and helium (flow rate of 25 L / min), and no hydrogen is introduced. After sieving, spherical powder of tantalum-tungsten alloy (Ta2.5W) with a particle size range of 15-53 μm and a sphericity of 99.3% is obtained.

[0155] Finally, low-oxygen tantalum-tungsten alloy spherical powder was obtained with a yield of 70%, and its chemical composition is shown in Table 9:

[0156] Table 9

[0157]

[0158] Example 7

[0159] The preparation method is the same as in Example 1, except that no passivation treatment was performed.

[0160] After spheroidization and sieving, spherical powder of tantalum-tungsten alloy (Ta2.5W) with a particle size range of 15-53μm and a sphericity of 99.4% was obtained.

[0161] Finally, spherical tantalum-tungsten alloy powder was obtained with a yield of 70%, and its chemical composition is shown in Table 10:

[0162] Table 10

[0163]

[0164] Example 8

[0165] Referring to the preparation method of Example 1, the difference is that in the passivation process of step (5), the four-stage argon-oxygen ratio control method was not used. Instead, a constant argon flow rate of 1.8 L / min and an oxygen-argon mixture flow rate of 2 L / min were continuously introduced throughout the process, and the total passivation time was 90 min.

[0166] After spheroidization and sieving, spherical powder of tantalum-tungsten alloy (Ta2.5W) with a particle size range of 15-53μm and a sphericity of 99.2% was obtained.

[0167] Finally, spherical tantalum-tungsten alloy powder was obtained with a yield of 68%, and its chemical composition is shown in Table 11:

[0168] Table 11

[0169]

[0170] Example 9

[0171] The preparation method is the same as in Example 1, except that the acid washing treatment in step (6) is a mixed acid composed of hydrofluoric acid (concentration 50%), nitric acid (concentration 65%) and hydrochloric acid (concentration 37%).

[0172] After spheroidization and sieving, spherical powder of tantalum-tungsten alloy (Ta2.5W) with a particle size range of 15-53μm and a sphericity of 99.4% was obtained.

[0173] Low-oxygen tantalum-tungsten alloy spherical powder was obtained with a yield of 65%, and its chemical composition is shown in Table 12.

[0174] Table 12

[0175]

[0176] Example 10

[0177] The 15-53μm Ta2.5W spherical powder prepared in Example 1 was used for SLM forming. The process parameters were: laser power of 270W, scanning speed of 650mm / s, scanning spacing of 150μm, and powder layer thickness of 30μm, to obtain tantalum-tungsten alloy (Ta2.5W) products with a density of 99.47%.

[0178] The formed tantalum-tungsten alloy (Ta2.5W) product was heat-treated at 1200℃ for 120 min to obtain a tantalum-tungsten alloy (Ta2.5W) product with a room temperature tensile strength of 768.38 MPa and an elongation of 34.06%. A photograph of the spherical tantalum-tungsten alloy product is shown below. Figure 6 .

[0179] Example 11

[0180] The 15-53μm Ta5.5W spherical powder prepared in Example 2 was used for SLM forming. The process parameters were: laser power of 270W, scanning speed of 550mm / s, scanning spacing of 150μm, and powder layer thickness of 30μm, to obtain tantalum-tungsten alloy (Ta5.5W) products with a density of 99.23%.

[0181] The formed tantalum-tungsten alloy (Ta5.5W) product was heat-treated at 1200℃ for 120 min to obtain a tantalum-tungsten alloy (Ta5.5W) product with a room temperature tensile strength of 767.53 MPa and an elongation of 33.74%.

[0182] Example 12

[0183] The 5-25μm Ta10W spherical powder prepared in Example 3 was used for SLM forming. The process parameters were: laser power of 270W, scanning speed of 800mm / s, scanning spacing of 130μm, and powder layer thickness of 20μm, to obtain tantalum-tungsten alloy (Ta10W) products with a density of 99.68%.

[0184] The formed tantalum-tungsten alloy (Ta10W) product was heat-treated at 1200℃ for 120 min to obtain a tantalum-tungsten alloy (Ta10W) product with a room temperature tensile strength of 766.15 MPa and an elongation of 35.34%.

[0185] Example 13

[0186] The 15-53μm Ta10W spherical powder prepared in Example 4 was used for SLM forming. The process parameters were: laser power of 300W, scanning speed of 550mm / s, scanning spacing of 140μm, and powder layer thickness of 30μm, to obtain tantalum-tungsten alloy (Ta10W) products with a density of 99.59%.

[0187] The formed tantalum-tungsten alloy (Ta10W) product was heat-treated at 1200℃ for 120 min to obtain a tantalum-tungsten alloy (Ta10W) product with a room temperature tensile strength of 770.99 MPa and an elongation of 30.66%. A photograph of the spherical tantalum-tungsten alloy product is shown below. Figure 7 .

[0188] Example 14

[0189] The 45-105μm Ta10W spherical powder prepared in Example 5 was used for SEBM forming. The process parameters were: substrate preheating temperature of 900℃, beam current of 25mA, scanning speed of 800mm / s, scanning spacing of 100μm, and powder layer thickness of 60μm, to obtain tantalum-tungsten alloy (Ta10W) products with a density of 99.76%.

[0190] The formed tantalum-tungsten alloy (Ta10W) product was heat-treated at 1200℃ for 120 min to obtain a tantalum-tungsten alloy (Ta10W) product with a room temperature tensile strength of 776.21 MPa and an elongation of 35.35%.

[0191] Comparative Example 1

[0192] The preparation method of Example 1 is different in that after hydrogenation and crushing in step (2), dehydrogenation and deoxygenation treatment in step (4) is performed first, and then plasma spheroidization treatment in step (3) is performed.

[0193] After spheroidization and sieving, spherical powder of tantalum-tungsten alloy (Ta2.5W) with a particle size range of 15-53μm and a sphericity of 98.5% was obtained.

[0194] Finally, spherical tantalum-tungsten alloy powder was obtained with a yield of 68%, and its chemical composition is shown in Table 13:

[0195] Table 13

[0196]

[0197] Comparative Example 2

[0198] Referring to the preparation method of Example 1, the difference is that in the hydrogenation treatment stage of step (2), a two-stage hydrogenation process is adopted. The specific steps are as follows: first, the alloy is heated to 750°C and held for 4 hours, then the temperature is further increased to 800°C and held for 2 hours, while hydrogen gas is introduced until the system pressure reaches 0.19 MPa; then, during the cooling process, hydrogen is continued to be introduced and adsorbed in the alloy, and the hydrogen supply is stopped when the actual temperature drops to 100°C. Tantalum-tungsten alloy hydride precursor powder with a particle size range of 15~53μm is obtained as the main product, with a yield of 63% and a hydrogen content of 1.03%.

[0199] After spheroidization and sieving, spherical powder of tantalum-tungsten alloy (Ta2.5W) with a particle size range of 15-53μm and a sphericity of 99.6% was obtained.

[0200] Finally, low-oxygen tantalum-tungsten alloy spherical powder was obtained with a yield of 57%, and its chemical composition is shown in Table 14:

[0201] Table 14

[0202]

[0203] Comparative Example 3

[0204] The preparation method is the same as in Example 1, except that the first stage of hydrogenation is performed by heating to 260°C under a hydrogen pressure of 0.03 MPa and holding for 2 hours. Tantalum-tungsten alloy hydride precursor powder with a particle size range of 15~53 μm is obtained as the main product, with a yield of 58% and a hydrogen content of 0.85%.

[0205] After spheroidization and sieving, spherical powder of tantalum-tungsten alloy (Ta2.5W) with a particle size range of 15-53μm and a sphericity of 98.1% was obtained.

[0206] Finally, low-oxygen tantalum-tungsten alloy spherical powder was obtained with a yield of 51%, and its chemical composition is shown in Table 15:

[0207] Table 15

[0208]

[0209] Comparative Example 4

[0210] The preparation method is the same as in Example 1, except that the first stage of hydrogenation is performed by heating to 620°C under a hydrogen pressure of 0.03 MPa and holding for 2 hours. Tantalum-tungsten alloy hydride precursor powder with a particle size range of 15-53 μm is obtained as the main product, with a yield of 50% and a hydrogen content of 1.12%.

[0211] After spheroidization and sieving, spherical powder of tantalum-tungsten alloy (Ta2.5W) with a particle size range of 15-53μm and a sphericity of 99.1% was obtained.

[0212] Finally, low-oxygen tantalum-tungsten alloy spherical powder was obtained with a yield of 46%, and its chemical composition is shown in Table 16:

[0213] Table 16

[0214]

[0215] Comparative Example 5

[0216] The preparation method is the same as in Example 1, except that a second hydrogenation treatment is performed: the hydrogen pressure is increased to 0.06 MPa and the temperature is raised to 820°C and held for 0.5 h. Tantalum-tungsten alloy hydride precursor powder with a particle size range of 15~53 μm is obtained as the main product, with a yield of 56% and a hydrogen content of 0.86%.

[0217] After spheroidization and sieving, spherical powder of tantalum-tungsten alloy (Ta2.5W) with a particle size range of 15-53μm and a sphericity of 97.6% was obtained.

[0218] Finally, low-oxygen tantalum-tungsten alloy spherical powder was obtained with a yield of 51%, and its chemical composition is shown in Table 17:

[0219] Table 17

[0220]

[0221] Comparative Example 6

[0222] The preparation method is the same as in Example 1, except that the second stage of hydrogenation is performed: the hydrogen pressure is increased to 0.06 MPa and the temperature is raised to 1250 °C and held for 0.5 h. Tantalum-tungsten alloy hydride precursor powder with a particle size range of 15~53 μm is obtained as the main product, with a yield of 47% and a hydrogen content of 1.06%.

[0223] After spheroidization and sieving, spherical powder of tantalum-tungsten alloy (Ta2.5W) with a particle size range of 15-53μm and a sphericity of 99.3% was obtained.

[0224] Finally, low-oxygen tantalum-tungsten alloy spherical powder was obtained with a yield of 43%, and its chemical composition is shown in Table 18:

[0225] Table 18

[0226]

[0227] Comparative Example 7

[0228] Following the preparation method of Example 1, the difference lies in the third stage of hydrogenation: the hydrogen pressure was adjusted back to 0.03 MPa and the temperature was lowered to 260°C and held for 1 hour. Tantalum-tungsten alloy hydride precursor powder with a particle size range of 15~53 μm was obtained as the main product, with a yield of 52% and a hydrogen content of 0.91%.

[0229] After spheroidization and sieving, spherical powder of tantalum-tungsten alloy (Ta2.5W) with a particle size range of 15-53μm and a sphericity of 98.2% was obtained.

[0230] Finally, low-oxygen tantalum-tungsten alloy spherical powder was obtained with a yield of 48%, and its chemical composition is shown in Table 19:

[0231] Table 19

[0232]

[0233] Comparative Example 8

[0234] The preparation method is the same as in Example 1, except that the third stage of hydrogenation is performed: the hydrogen pressure is adjusted back to 0.03 MPa and the temperature is lowered to 620°C and held for 1 hour. Tantalum-tungsten alloy hydride precursor powder with a particle size range of 15~53 μm is obtained as the main product, with a yield of 45% and a hydrogen content of 1.13%.

[0235] After spheroidization and sieving, spherical powder of tantalum-tungsten alloy (Ta2.5W) with a particle size range of 15-53μm and a sphericity of 99.7% was obtained.

[0236] Finally, low-oxygen tantalum-tungsten alloy spherical powder was obtained with a yield of 41%, and its chemical composition is shown in Table 20:

[0237] Table 20

[0238]

[0239] Test case

[0240] For the tantalum-tungsten alloy spherical powders prepared in Examples 1-9 and Comparative Examples 1-8, the hydrogen content of the tantalum-tungsten alloy hydride precursor powder was determined by inert gas melting-infrared absorption method to evaluate the hydrogenation effect. The sphericity of the final powder was statistically calculated using scanning electron microscopy image analysis to evaluate the sphericity effect. The oxygen content of the spherical powder was determined by inert gas melting-infrared method to verify the effectiveness of the dehydrogenation, deoxygenation, and passivation pickling processes in controlling impurity elements. Furthermore, by accurately measuring the mass of the precursor powder (M1) within the sieved particle size range, the mass of the finally obtained spherical powder (M2) corresponding to the target particle size range, and the ingot mass (M3), the yield of the precursor powder of the target particle size (Y1=M1 / M3×100%) and the yield of the spherical powder (Y2=M2 / M3×100%) were calculated to quantitatively evaluate the process efficiency and economy of this preparation method in reducing ineffective fine powder and increasing the yield of effective products. The above characterization results are summarized in Table 21.

[0241] For the products obtained by SLM or SEBM forming and heat treatment in Examples 10-14, the density was determined by Archimedes' displacement method to evaluate the densification ability of the forming process, and the tensile strength and elongation of the products were obtained by room temperature quasi-static tensile testing using a universal testing machine to comprehensively characterize their mechanical properties. The above characterization results are summarized in Table 22.

[0242] Table 21

[0243]

[0244] Table 22

[0245]

[0246] Based on the above test data analysis, it can be seen that: Examples 1-9 of the present invention, through a three-stage hydrogenation process, precisely control the hydrogen content of the precursor powder within the range of 0.90%~0.95%, and adopt a process sequence of spheroidization followed by dehydrogenation and gradient passivation treatment, so that the sphericity of the final spherical powder reaches 99.0%~99.6%, the oxygen content is as low as 0.0076%~0.015%, the precursor powder yield reaches 73%~80%, and the spherical powder yield reaches 67%~72%. In contrast, Comparative Example 1, due to dehydrogenation followed by spheroidization, resulted in a decrease in sphericity to 98.5% and an increase in oxygen content to 0.024%; Comparative Example 2, due to two-stage hydrogenation, resulted in a higher hydrogen content (1.03%), a decrease in the precursor powder yield to 63%, and a decrease in the spherical powder yield to 57%; Comparative Examples 3-8... Because the hydrogenation temperatures in each stage deviated from the range of this invention (first stage 260~620℃, second stage 820~1250℃, third stage 260~620℃), the hydrogen content was too high (1.06%~1.13%), the sphericity dropped to a minimum of 97.6%, the precursor powder yield decreased to 45%~58%, and the spherical powder yield decreased to 41%~51%. In Example 6, no hydrogen was introduced, so the oxygen content increased slightly to 0.014%. In Example 7, no passivation treatment was performed, and the sample was directly exposed to the atmosphere (oxygen content was about 21%), so the oxygen content increased to 0.025%. In Example 8, no graded passivation treatment was performed, and the atmospheric oxygen content was 22-26%, so the oxygen content increased to 0.027%. In Example 9, acid washing with mixed strong acid reduced the spherical powder yield to 65%. The products obtained by SLM or SEBM molding using the powder of the present invention (Examples 10-14) all have a density of over 99.23%, and after heat treatment, the tensile strength is over 766 MPa and the elongation is over 30%, which fully demonstrates that the method of the present invention has significant advantages in terms of hydrogenation controllability, spheroidization effect, impurity control, yield and additive manufacturing adaptability.

Claims

1. A method for preparing tantalum-tungsten alloy spherical powder, characterized in that, Includes the following steps: (1) Raw material preparation and smelting: Tantalum and tungsten metal raw materials are mixed in a preset ratio, and then vacuum degassing and electron beam smelting are performed to obtain tantalum-tungsten alloy ingots with uniform composition. (2) Hydrogenation and crushing treatment: The ingot is subjected to segmented hydrogenation treatment, which includes the following steps: a) Keep warm at 0.01~0.04MPa and 300~500℃ for 1~3h; b) Hold at 0.04~0.08MPa and 900~1000℃ for 0.5~1h; c) Keep warm at 0.02~0.05MPa and 300~400℃ for 0.5~1.5h; Subsequently, based on the particle size requirements of the end product, the hydrogenated and embrittled alloy was mechanically crushed and sieved to obtain tantalum-tungsten alloy hydride precursor powder with a hydrogen content of 0.8~1.0wt%. (3) Plasma spheroidization treatment: The precursor powder is subjected to radio frequency plasma spheroidization to obtain tantalum-tungsten alloy spherical powder in the target particle size range; wherein the side gas is a mixture of argon, helium and hydrogen, wherein the argon flow rate is 45~100L / min, the helium flow rate is 20~40L / min and the hydrogen flow rate is 0.5~3.5L / min; (4) Dehydrogenation and oxygen reduction treatment: The tantalum-tungsten alloy spherical powder is mixed with magnesium powder and subjected to a three-stage heating treatment under alternating control of inert atmosphere and vacuum conditions, specifically: First stage, vacuum to vacuum degree ≤5×10 -3 Pa, argon to 0.1~0.2MPa, treatment temperature is 400~490℃, heat preservation 0.5~1h; The second stage involves setting the temperature and holding time based on the target particle size range, specifically as follows: When the target particle size range is 45~105μm, the processing temperature is 1000~1090℃, and the holding time is 3.5~5h; When the target particle size range is 15~53μm, the processing temperature is 900~990℃, and the holding time is 2.5~4h; When the target particle size range is 5~25μm, the processing temperature is 800~890℃, and the holding time is 2~3h; In the third stage, vacuum is drawn to a vacuum degree of ≤5×10 -3 Pa at the temperature of the second stage, and the holding time is set according to the target particle size interval, specifically: When the target particle size range is 45~105μm, keep warm for 2~3 hours; When the target particle size range is 15~53μm, keep warm for 1.5~2.5h; When the target particle size range is 5~25μm, keep warm for 1~1.5h; The added magnesium powder is 0.1 to 0.5 wt% of the mass of the tantalum-tungsten alloy spherical powder.

2. The preparation method according to claim 1, characterized in that, The preset proportion of ingredients is: 2.5~15wt% tungsten content, with the balance being tantalum.

3. The preparation method according to claim 1, characterized in that, In step (2), the process parameters for mechanical crushing are set according to the target particle size range, specifically as follows: When the target particle size range is 45~105μm, the mechanical crushing cycle is 1~3 times, and the single crushing time is 2~3 minutes. When the target particle size range is 15~53μm, the mechanical crushing cycle is 4~6 times, and the single crushing time is 2~5min; When the target particle size range is 5~25μm, the mechanical crushing cycle is 7~10 times and the single crushing time is 3~6min.

4. The preparation method according to claim 1, characterized in that, In step (3), the process parameters for radio frequency plasma spheroidization are: plasma power 30~100kW; central gas is argon, flow rate 15~40L / min; powder carrier gas is argon, flow rate 3~6L / min; powder feeding rate 30~60g / min; reaction chamber pressure 10~17psi.

5. The preparation method according to claim 1, characterized in that, Following step (4), the following post-processing steps are also included: (5) Passivation treatment: vacuum extraction to a vacuum degree of ≤5×10 -3 Pa, argon gas and mixed gas of argon and oxygen are introduced, and at least four stages of passivation cycles are performed, the oxygen concentration of each stage is controlled to be 1%~3%, 5%~8%, 12%~17% and 22%~26% in turn, and each stage lasts for 15~60 min. (6) Pickling treatment: The passivated powder is washed with a hydrochloric acid solution with a concentration of 15%~30%.

6. A method for additive manufacturing of a tantalum-tungsten alloy component, characterized in that, Using the tantalum-tungsten alloy spherical powder prepared by any one of claims 1-5 as raw material, a corresponding powder bed melting process is selected according to the particle size range of the tantalum-tungsten alloy spherical powder for forming: When the particle size range of the powder is 5~25μm or 15~53μm, laser selective melting process is adopted; When the particle size range of the powder is 45~105μm, electron beam selective melting process is adopted.

7. The additive manufacturing method according to claim 6, characterized in that, The parameters of the laser selective melting process are: laser power 150~400W, scanning speed 200~800mm / s, scanning spacing 70~150μm, and powder layer thickness 20~40μm. The parameters of the electron beam selective melting process are as follows: substrate preheating temperature 700~1000℃, beam current 10~25mA, scanning speed 400~1000mm / s, scanning spacing 50~200μm, and powder layer thickness 40~80μm.

8. The additive manufacturing method according to claim 6 or 7, characterized in that, After forming, a heat treatment step is also included, wherein the temperature of the heat treatment is 1000~1400℃ and the holding time is 60~180min.

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