A kind of TaNbTiZr refractory high entropy alloy spherical powder and preparation method thereof

Abstract

The invention discloses a TaNbTiZr refractory high entropy alloy spherical powder and a preparation method thereof. The preparation method is: Ta and Ti are smelted to obtain a TaTi master alloy, Nb and Zr are smelted to obtain a NbZr master alloy, and then the TaTi master alloy and the NbZr master alloy are smelted to obtain a TaNbTiZr refractory high entropy alloy ingot, and the first hydrogenation treatment, dehydrogenation treatment, second hydrogenation treatment, and ball milling treatment are sequentially performed to obtain refractory high entropy alloy hydride particles, and then the refractory high entropy alloy hydride particles are subjected to plasma spheroidization treatment to obtain a single-phase BCC structure TaNbTiZr refractory high entropy alloy spherical powder, and the powder particle size is 30-150μm. The preparation method of the present invention has a simple process, a high powder yield, is not restricted by the size and shape of the ingot, does not need to prepare a rod-shaped refractory high entropy alloy, and the powder particle size distribution is controllable, the composition is uniform, the sphericity is high, and the fluidity is good.

Description

Technical Field

[0001] The invention relates to the field of high entropy alloys, and mainly to TaNbTiZr refractory high entropy alloy spherical powder and a preparation method thereof. Background Art

[0002] The concept of refractory high entropy alloy was first proposed in 2010. It is a relatively mature alloy system under the concept of high entropy alloy. The system is mainly composed of high melting point elements (such as Nb, Mo, Hf, Ta, W) in equiatomic ratio or near atomic ratio, and also includes some non-refractory elements (such as Al, Ti, V, Cr, Zr, etc.). The huge difference in the properties of the elements brings strong lattice distortion effect and hysteresis diffusion effect to refractory high entropy alloys, making them show excellent thermal stability and good high-temperature mechanical properties. It is expected to replace traditional nickel-based high-temperature alloys and has broad application prospects in extremely complex environments such as aerospace and nuclear industry. However, the complex composition elements and large differences in element melting points hinder the preparation of refractory high entropy alloys. Therefore, the preparation of refractory high entropy alloys in current research mostly adopts vacuum melting method, but the melted ingots have defects such as coarse grains, component segregation and loose pores. In addition, the ingots are irregular in shape and have poor processing performance.

[0003] Powder metallurgy and additive manufacturing have the characteristics of near-net shaping, and can prepare materials of any complex shape. The prepared refractory high-entropy alloys have fine grains, uniform composition, and high density. Based on the advantages of powder metallurgy, the preparation of high-quality refractory high-entropy alloy powders is particularly important, and the requirements for powders in fields such as additive manufacturing and thermal spraying are further improved, which is reflected in the high sphericity, good fluidity and suitable particle size distribution of the powder. Therefore, the preparation of high-sphericity refractory high-entropy alloy powders is an important basis for powder metallurgy refractory high-entropy alloy materials. At present, the preparation of spherical alloy powders mainly adopts gas atomization and water atomization, but the existing atomization powder making equipment is difficult to reach the melting point of refractory high-entropy alloys during smelting, and the sphericity of the prepared powder is low. Summary of the invention

[0004] In view of the deficiencies mentioned in the above background technology, the first object of the present invention is to provide a method for preparing TaNbTiZr refractory high entropy alloy spherical powder with good sphericity, uniform composition, uniform particle size distribution and good fluidity.

[0005] The second object of the present invention is to provide TaNbTiZr refractory high entropy alloy spherical powder prepared by the above preparation method.

[0006] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0007] The invention provides a method for preparing a TaNbTiZr refractory high entropy alloy spherical powder. The method comprises the following steps: smelting Ta and Ti to obtain a TaTi master alloy, smelting Nb and Zr to obtain a NbZr master alloy, then smelting the TaTi master alloy and the NbZr master alloy to obtain a TaNbTiZr refractory high entropy alloy ingot, sequentially performing a first hydrogenation treatment, a dehydrogenation treatment, a second hydrogenation treatment and a ball milling treatment on the TaNbTiZr refractory high entropy alloy ingot to obtain refractory high entropy alloy hydride particles, and then performing a plasma spheroidization treatment on the refractory high entropy alloy hydride particles to obtain the TaNbTiZr refractory high entropy alloy spherical powder.

[0008] TaNbTiZr refractory high entropy alloy has high component content and high melting point. The conventional method is used to directly smelt Ta, Nb, Ti, and Zr as raw materials to prepare TaNbTiZr refractory high entropy alloy, which will cause serious segregation of Ta elements and Ti elements, affecting the composition uniformity of the final product. The present invention first obtains TaTi master alloy and NbZr master alloy by smelting respectively, and then smelts TaTi master alloy and NbZr master alloy together, that is, obtains TaNbTiZr refractory high entropy alloy ingot with uniform composition, but TaNbTiZr refractory high entropy alloy ingot has good ductility, and it is difficult to directly grind and crush it. It is necessary to increase the brittleness of the material after hydrogenation treatment to obtain a better crushing effect. However, the hardness of TaNbTiZr refractory high entropy alloy hydride is very high, and the efficiency will be very low if the conventional hydrogenation-crushing method is adopted. Therefore, the present invention proposes a crushing treatment method of hydrogenation-dehydrogenation-hydrogenation-ball milling, wherein the brittleness of the TaNbTiZr refractory high entropy alloy ingot increases after the first hydrogenation, and after the dehydrogenation treatment, the ingot will be broken into small particles due to the hydrogen evolution explosion effect, and the brittleness of the small particles will increase after the second hydrogenation, and finally, after the ball milling treatment, the refractory high entropy alloy hydride particles with a particle size of less than 100 mesh can be obtained. The refractory high entropy alloy hydride particles are then subjected to plasma spheroidization. Since the center temperature of the plasma torch is as high as 8000K or more, the metal hydride can be decomposed into metal droplets and hydrogen at this temperature, and the hydrogen is discharged by the exhaust system of the ion spheroidization equipment, and the metal droplets spontaneously form spheres under the action of surface tension, so as to obtain a spherical high entropy alloy powder with high purity and low impurity content.

[0009] In the above preparation method, preferably, the purity of Ta, Ti, Nb and Zr are all ≥99.9%.

[0010] In the above preparation method, preferably, Ta and Ti are subjected to vacuum arc melting 3 to 5 times to obtain a TaTi intermediate alloy, Nb and Zr are subjected to vacuum arc melting 3 to 5 times to obtain a NbZr intermediate alloy, and then the TaTi intermediate alloy and the NbZr intermediate alloy are subjected to vacuum arc melting 3 to 5 times to obtain a TaNbTiZr refractory high entropy alloy ingot.

[0011] The inventors have found that only by combining the highest melting point component Ta and the lowest melting point component Ti, and combining the medium melting point components Nb and Zr, can the melting points of the intermediate alloy be close, so that during the secondary smelting, serious segregation will not be caused due to the complex melting points of the components. If the combination method is different from the present invention, it is also impossible to obtain a TaNbTiZr refractory high entropy alloy ingot with uniform composition.

[0012] In the above preparation method, preferably, the temperature of the first hydrogenation treatment is 550-600° C., and the time of the first hydrogenation treatment is 2-4 hours.

[0013] In the above preparation method, preferably, during the first hydrogenation treatment, the flow rate of hydrogen introduced is 1 to 5 L / min.

[0014] In the above preparation method, preferably, the dehydrogenation treatment is carried out in a vacuum environment, the temperature of the dehydrogenation treatment is 800-850° C., the time of the dehydrogenation treatment is 2-4 h, and the vacuum degree is ≤0.05 Pa.

[0015] In the above preparation method, preferably, the temperature of the second hydrogenation treatment is 550-600° C., and the time of the second hydrogenation treatment is 2-4 hours.

[0016] In the above preparation method, preferably, during the second hydrogenation treatment, the flow rate of hydrogen introduced is 1 to 5 L / min.

[0017] The inventors found that the best effect is achieved when the temperature of the two hydrogenation treatments and the dehydrogenation treatment is controlled within the above range. If the hydrogenation temperature is too high, the Nb element cannot be hydrogenated, and if the hydrogenation temperature is too low, the Zr element cannot be hydrogenated. Both situations will lead to poor alloy hydrogenation effect, which in turn leads to poor subsequent crushing effect. In addition, during the dehydrogenation process, if the dehydrogenation temperature is too high, the Nb element cannot be dehydrogenated, and if the dehydrogenation temperature is too low, the Ta element cannot be dehydrogenated. Both situations will lead to poor alloy dehydrogenation effect.

[0018] In the above preparation method, preferably, the rotation speed of the ball milling treatment is 200-300 rpm, the time of the ball milling treatment is 5-20 h, and the ball-to-material ratio is (5-10):1.

[0019] In the above preparation method, preferably, during the ball milling process, the materials of the ball milling jar and the grinding balls used are both cemented carbide.

[0020] The preparation method of the present invention can obtain refractory high entropy alloy hydride particles with a particle size of less than 100 meshes after ball milling treatment, and the obtained refractory high entropy alloy hydride particles are irregular in shape. The refractory high entropy alloy hydride particles are then spheroidized by a plasma spheroidization method to obtain spherical powders with high sphericity and uniform particle size distribution.

[0021] The present invention adopts a ball mill and grinding balls made of cemented carbide in the ball milling process, which can solve the wear and pollution problem of the ball mill and grinding balls caused by the high hardness of TaNbTiZr refractory high entropy alloy hydride particles, and is beneficial to reducing impurity elements such as Fe and Cr in the TaNbTiZr refractory high entropy alloy spherical powder.

[0022] In the above preparation method, preferably, the particle size of the refractory high entropy alloy hydride particles is less than 100 mesh.

[0023] In the above preparation method, preferably, the process parameters of the plasma spheroidization are: a carrier gas flow rate of 40 to 60 slm, a center gas flow rate of 30 to 40 slm, and a sheath gas flow rate of 60 to 80 slm, wherein the carrier gas, the center gas, and the sheath gas all use argon with a purity of ≥99.999%, the plasma power is 12 to 15 kW, the reaction chamber pressure is 7.5 to 15 psia, and the powder feeding rate is 5 to 10 g / min.

[0024] The present invention also provides TaNbTiZr refractory high entropy alloy spherical powder prepared by the above preparation method. The TaNbTiZr refractory high entropy alloy spherical powder has a BCC single-phase structure, a powder particle size of 30 to 150 μm, and a powder sphericity of ≥0.95.

[0025] Compared with the prior art, the advantages of the present invention are:

[0026] (1) The two-step smelting method can solve the segregation problem of TaNbTiZr refractory high entropy alloy ingots, which is conducive to obtaining highly uniform TaNbTiZr refractory high entropy alloy spherical powders.

[0027] (2) The granulation process of hydrogenation-dehydrogenation-hydrogenation-ball milling can solve the problem of difficult crushing and low efficiency of TaNbTiZr refractory high entropy alloy, which is conducive to obtaining TaNbTiZr refractory high entropy alloy hydride particles with finer particle size.

[0028] (3) The use of carbide ball mills and grinding balls can solve the wear and contamination problem of the ball mills and grinding balls caused by the high hardness of the TaNbTiZr refractory high entropy alloy hydride particles, which is beneficial to reducing the impurity elements such as Fe and Cr in the TaNbTiZr refractory high entropy alloy spherical powder.

[0029] (4) Plasma spheroidization is used to prepare TaNbTiZr refractory high entropy alloy spherical powder. Since the center temperature of the plasma torch is as high as 8000K or above, metal hydride can be decomposed into metal droplets and hydrogen at this temperature. The hydrogen is discharged by the exhaust system of the ion spheroidization equipment, and the metal droplets spontaneously form spheres under the action of surface tension to obtain spherical high entropy alloy powder. Therefore, the plasma spheroidization process has a certain impurity removal ability, which is conducive to obtaining high-purity, low-impurity TaNbTiZr refractory high entropy alloy spherical powder.

[0030] (5) The TaNbTiZr refractory high entropy alloy spherical powder prepared by the present invention has high sphericity, no satellite powder and hollow powder, good fluidity, and can meet the high quality requirements of raw material powder in the fields of additive manufacturing and thermal spraying.

[0031] (6) The preparation method of the present invention has a simple process, a high powder yield, is not restricted by the size and shape of the ingot, does not require the preparation of rod-shaped refractory high-entropy alloys, and has a controllable powder particle size distribution, uniform composition, high sphericity, and good fluidity. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The XRD spectrum of the TaNbTiZr refractory high entropy alloy spherical powder prepared in Example 1 of the present invention is as follows:

[0033] Figure 2 This is a SEM photograph of the TaNbTiZr refractory high entropy alloy spherical powder prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0034] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the present invention, but the protection scope of the present invention is not limited to the following specific embodiments.

[0035] Unless otherwise defined, all the professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0036] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0037] In the following examples, pure metal blocks were purchased from the market with a purity higher than 99.9%. The model of the plasma spheroidization device was TEKNA-15, and the purity of the argon gas used in the plasma spheroidization system was higher than 99.999%.

[0038] Embodiment 1:

[0039] Preparation method of TaNbTiZr refractory high entropy alloy spherical powder

[0040] (1) Ta, Nb, Ti, and Zr blocks with a purity of more than 99.9% are used as raw materials, Ta and Ti as well as Nb and Zr are weighed according to an atomic fraction of 1:1, and the raw materials are placed in a water-cooled copper crucible of a vacuum arc melting furnace. Argon is used as a protective gas and an arc-starting gas, and the intermediate alloy is repeatedly melted for 3 times, and the alloy is kept in a liquid state for more than 10 minutes to obtain TaTi intermediate alloys and NbZr intermediate alloys. Then, TaTi intermediate alloys and NbZr intermediate alloys are used as raw materials, and TaNbTiZr refractory high entropy alloy ingots are obtained by repeatedly melting them 3 times by vacuum arc melting.

[0041] (2) The ingot melted in step (1) is placed in a hydrogen sintering furnace, 99.999% high-purity hydrogen is introduced into the furnace body, the sintering temperature is controlled to 600°C, the holding time is 2h, the hydrogen flow rate is 5L / min, and the TaNbTiZr refractory high entropy alloy hydride ingot is obtained after cooling out of the furnace. Then it is placed in a vacuum sintering furnace, the sintering temperature is controlled to 850°C, the holding time is 4h, the vacuum degree is lower than 0.05Pa, and the TaNbTiZr refractory high entropy alloy coarse particles are obtained after cooling out of the furnace. Then it is placed in a hydrogen sintering furnace, 99.999% high-purity hydrogen is introduced into the furnace body, the sintering temperature is controlled to 600°C, the holding time is 2h, the hydrogen flow rate is 5L / min, and the TaNbTiZr refractory high entropy alloy hydride coarse particles are obtained after cooling out of the furnace. Finally, the particles were placed in a planetary ball mill for ball milling and crushing, with the ball milling speed controlled at 200 rpm, the ball milling time at 15 h, and the ball-to-material ratio at 10:1, to obtain TaNbTiZr refractory high entropy alloy hydride fine particles.

[0042] (3) The alloy hydride fine particles screened in step (2) are placed in a plasma spheroidization device, and the carrier gas flow rate is set to 60 slm, the center gas flow rate is set to 40 slm, the sheath gas flow rate is set to 80 slm, the plasma power is set to 15 kW, the reaction chamber pressure is set to 15 psia, and the powder feeding rate is set to 10 g / min. After spheroidization treatment, TaNbTiZr refractory high entropy alloy spherical powder is obtained.

[0043] Figure 1 This is the XRD spectrum of TaNbTiZr refractory high entropy alloy spherical powder, and the surface of the powder is a BCC single-phase structure. Figure 2 This is a SEM photo of TaNbTiZr refractory high entropy alloy spherical powder. It can be seen from the figure that the refractory high entropy alloy spherical powder has high sphericity and uniform particle size distribution. After testing, the average particle size of the prepared TaNbTiZr refractory high entropy alloy spherical powder is 76μm, and the powder sphericity is 0.98.

[0044] Embodiment 2:

[0045] Preparation method of TaNbTiZr refractory high entropy alloy spherical powder

[0046] (1) Ta, Nb, Ti, and Zr blocks with a purity of more than 99.9% are used as raw materials, Ta and Ti as well as Nb and Zr are weighed according to an atomic fraction of 1:1, and the raw materials are placed in a water-cooled copper crucible of a vacuum arc melting furnace. Argon is used as a protective gas and an arc-starting gas, and the intermediate alloy is repeatedly melted for 5 times, and the alloy is kept in a liquid state for more than 10 minutes to obtain TaTi intermediate alloys and NbZr intermediate alloys. Then, TaTi intermediate alloys and NbZr intermediate alloys are used as raw materials, and TaNbTiZr refractory high entropy alloy ingots are obtained by repeatedly melting them 5 times by vacuum arc melting.

[0047] (2) The ingot melted in step (1) is placed in a hydrogen sintering furnace, 99.999% high-purity hydrogen is introduced into the furnace body, the sintering temperature is controlled to be 550°C, the holding time is 4h, the hydrogen flow rate is 2L / min, and the TaNbTiZr refractory high entropy alloy hydride ingot is obtained after cooling out of the furnace. Then it is placed in a vacuum sintering furnace, the sintering temperature is controlled to be 800°C, the holding time is 4h, the vacuum degree is lower than 0.05Pa, and the TaNbTiZr refractory high entropy alloy coarse particles are obtained after cooling out of the furnace. Then it is placed in a hydrogen sintering furnace, 99.999% high-purity hydrogen is introduced into the furnace body, the sintering temperature is controlled to be 550°C, the holding time is 4h, the hydrogen flow rate is 2L / min, and the TaNbTiZr refractory high entropy alloy hydride coarse particles are obtained after cooling out of the furnace. Finally, the particles were placed in a planetary ball mill for ball milling and crushing, with the ball milling speed controlled at 300 rpm, the ball milling time at 5 h, and the ball-to-material ratio at 5:1, to obtain TaNbTiZr refractory high entropy alloy hydride fine particles.

[0048] (3) The alloy hydride fine particles screened in step (2) are placed in a plasma spheroidization device, and the carrier gas flow rate is set to 45 slm, the center gas flow rate is set to 30 slm, the sheath gas flow rate is set to 60 slm, the plasma power is set to 12 kW, the reaction chamber pressure is set to 10 psia, and the powder feeding rate is set to 5 g / min. After spheroidization treatment, TaNbTiZr refractory high entropy alloy spherical powder is obtained.

[0049] After testing, the prepared TaNbTiZr refractory high entropy alloy spherical powder has a BCC single-phase structure, an average powder particle size of 52 μm, and a powder sphericity of 0.99.

[0050] Embodiment 3:

[0051] Preparation method of TaNbTiZr refractory high entropy alloy spherical powder

[0052] (1) Ta, Nb, Ti, and Zr blocks with a purity of more than 99.9% are used as raw materials, Ta and Ti as well as Nb and Zr are weighed according to an atomic fraction of 1:1, and the raw materials are placed in a water-cooled copper crucible of a vacuum arc melting furnace. Argon is used as a protective gas and an arc-starting gas, and the intermediate alloy is repeatedly melted for 5 times, and the alloy is kept in a liquid state for more than 10 minutes to obtain TaTi intermediate alloys and NbZr intermediate alloys. Then, TaTi intermediate alloys and NbZr intermediate alloys are used as raw materials, and TaNbTiZr refractory high entropy alloy ingots are obtained by repeatedly melting them 5 times by vacuum arc melting.

[0053] (2) The ingot melted in step (1) is placed in a hydrogen sintering furnace, 99.999% high-purity hydrogen is introduced into the furnace body, the sintering temperature is controlled to be 580°C, the holding time is 3h, the hydrogen flow rate is 3.5L / min, and the TaNbTiZr refractory high entropy alloy hydride ingot is obtained after cooling out of the furnace. Then it is placed in a vacuum sintering furnace, the sintering temperature is controlled to be 800°C, the holding time is 3h, the vacuum degree is lower than 0.05Pa, and the TaNbTiZr refractory high entropy alloy coarse particles are obtained after cooling out of the furnace. Then it is placed in a hydrogen sintering furnace, 99.999% high-purity hydrogen is introduced into the furnace body, the sintering temperature is controlled to be 580°C, the holding time is 3h, the hydrogen flow rate is 3.5L / min, and the TaNbTiZr refractory high entropy alloy hydride coarse particles are obtained after cooling out of the furnace. Finally, the particles were placed in a planetary ball mill for ball milling and crushing, with the ball milling speed controlled at 250 rpm, the ball milling time at 10 h, and the ball-to-material ratio at 5:1, to obtain TaNbTiZr refractory high entropy alloy hydride fine particles.

[0054] (3) The alloy hydride fine particles screened in step (2) are placed in a plasma spheroidization device, and the carrier gas flow rate is set to 40 slm, the center gas flow rate is set to 30 slm, the sheath gas flow rate is set to 70 slm, the plasma power is set to 14.5 kW, the reaction chamber pressure is set to 10 psia, and the powder feeding rate is set to 10 g / min. After spheroidization treatment, TaNbTiZr refractory high entropy alloy spherical powder is obtained.

[0055] After testing, the prepared TaNbTiZr refractory high entropy alloy spherical powder has a BCC single-phase structure, an average powder particle size of 65 μm, and a powder sphericity of 0.98.

[0056] Comparative Example 1:

[0057] According to the parameters of Example 1, TaNbTiZr refractory high entropy alloy spherical powder was prepared, and the process was continued to step (2), the ball milling speed was adjusted to 150 r / min, the ball milling time was adjusted to 5 h, the ball-to-material ratio remained unchanged, and the metal hydride was ball milled. The remaining steps were performed in the same process to obtain TaNbTiZr refractory high entropy alloy spherical powder.

[0058] In this comparative example, the rotation speed of ball milling is adjusted to 150r / min, and the ball milling time is adjusted to 5h. The reduction of input energy and the reduction of crushing time affect the effect of ball milling, making it difficult for metal hydride to be completely crushed to the target particle size range, and some larger particles do not achieve the crushing effect. In the plasma spheroidization process, only the spheroidization of the powder can be achieved, and the particle size of the powder has not changed significantly. Therefore, the particle size of the powder after ball milling directly affects the particle size distribution of the spherical powder. In the plasma spheroidization process, powder feeding is achieved by a vibrating powder feeder. The particle size distribution of the powder that is too large or too small affects the stability of the powder feeding process, and even makes it difficult to achieve powder feeding. Therefore, the rotation speed and ball milling time in the ball milling process are important parameters of the present invention. The selection of reasonable ball milling process parameters is the key to efficiently crushing the metal hydride block to the target particle size range, and is the prerequisite for preparing a spherical powder with uniform particle size distribution.

[0059] Comparative Example 2:

[0060] TaNbTiZr refractory high entropy alloy spherical powder is prepared according to the parameters of Example 1, and step (3) is executed to adjust the powder feeding rate to 20 g / min, and then the powder is spheroidized according to the plasma spheroidization process parameters in Example 1 to obtain TaNbTiZr refractory high entropy alloy spherical powder.

[0061] In this comparative example, the powder feeding rate during the plasma spheroidization process is increased to 20g / min. When the power of the plasma spheroidization equipment is 15kW, the total amount of energy absorbed by the powder when passing through the plasma is constant. When the feeding rate is low, the energy absorbed by the powder from the plasma is high on average, which can achieve surface melting or complete melting of the powder, thereby achieving spheroidization of the powder; when the powder feeding rate is high, the average energy absorbed by the powder from the plasma is reduced, the powder is not fully spheroidized, and thus the high sphericity effect is not obtained. Therefore, the powder feeding rate in the present invention needs to be strictly controlled to achieve a good powder spheroidization effect.

[0062] Comparative Example 3:

[0063] According to the parameters of Example 1, TaNbTiZr refractory high entropy alloy spherical powder is prepared, and step (1) is performed to adjust the smelting scheme to first melt the TaNb master alloy and the TiZr master alloy, and then perform secondary smelting of the TaNb master alloy and the TiZr master alloy to prepare a TaNbTiZr refractory high entropy alloy ingot. Then, the remaining steps of Example 1 are followed to obtain TaNbTiZr refractory high entropy alloy spherical powder.

[0064] This comparative example adjusts the combination of the smelting master alloy. Although the refractory high entropy alloy powder obtained has high sphericity and uniform particle size, the alloy powder composition deviation is large, and there are a large number of TaNb-rich alloy powders and TiZr-rich alloy powders. The main reason is that the melting point difference between the TaNb master alloy and the TiZr master alloy is large during the secondary smelting process, and the large difference in the melting point of the raw materials during the smelting of multi-component alloys is prone to component segregation. Therefore, in the present invention, it is necessary to control the smelting of the TaTi master alloy and the NbZr master alloy first, and then perform secondary smelting to achieve a better component uniformity effect.

[0065] Comparative Example 4:

[0066] TaNbTiZr refractory high entropy alloy spherical powder was prepared according to the parameters of Example 2, and the step (2) was adjusted to not perform the front-end hydrogenation and dehydrogenation treatment, that is, only the back-end hydrogenation treatment and ball milling treatment were performed to obtain TaNbTiZr refractory high entropy alloy hydride fine particles. Subsequently, TaNbTiZr refractory high entropy alloy spherical powder was obtained according to the remaining steps of Example 2.

[0067] Although the refractory high entropy alloy powder obtained in this comparative example has high sphericity and uniform composition, the alloy powder particle size is coarse, and the average powder particle size reaches 162μm, which cannot meet the requirements of metal powder for additive manufacturing. The main reason is that without the front-end hydrogenation and dehydrogenation treatment, the effect of direct ball milling of the alloy hydrogenated ingot is poor. Under the same ball milling process, the obtained refractory high entropy alloy hydride fine particle size is coarse, resulting in a coarse particle size of the final powder product. Therefore, the present invention needs to carry out a first hydrogenation treatment, a dehydrogenation treatment, a second hydrogenation treatment, and a ball milling treatment to obtain refractory high entropy alloy hydride particles with controllable particle size in order to achieve a better powder preparation effect.

[0068] Comparative Example 5:

[0069] According to the parameters of Example 2, TaNbTiZr refractory high entropy alloy spherical powder was prepared, and step (2) was performed to adjust the hydrogenation temperature to 700°C and the dehydrogenation temperature to 900°C to obtain TaNbTiZr refractory high entropy alloy hydride fine particles. Then, according to the remaining steps of Example 2, TaNbTiZr refractory high entropy alloy spherical powder was obtained.

[0070] Although the refractory high entropy alloy powder obtained in this comparative example has high sphericity and uniform composition, the alloy powder particle size is also coarse, and the average powder particle size reaches 133 μm, which cannot meet the requirements of metal powder for additive manufacturing. The main reason is that the hydrogenation and dehydrogenation temperatures are high, which makes the Nb element unable to be hydrogenated and dehydrogenated, and the plasticity of the elemental Nb is very good, which causes the powder to easily adhere and agglomerate during the ball milling process, making the obtained refractory high entropy alloy hydride fine particle size coarse, resulting in a coarse particle size of the final powder product. Therefore, the present invention must strictly control the hydrogenation and dehydrogenation temperatures so that each component is fully hydrogenated / dehydrogenated to achieve a better powder preparation effect.

Claims

1. A method for preparing TaNbTiZr refractory high entropy alloy spherical powder, characterized in that: Ta and Ti are smelted to obtain a TaTi master alloy, Nb and Zr are smelted to obtain a NbZr master alloy, the TaTi master alloy and the NbZr master alloy are then smelted to obtain a TaNbTiZr refractory high entropy alloy ingot, the TaNbTiZr refractory high entropy alloy ingot is subjected to a first hydrogenation treatment, a dehydrogenation treatment, a second hydrogenation treatment, and a ball milling treatment in sequence to obtain refractory high entropy alloy hydride particles, and the refractory high entropy alloy hydride particles are subjected to a plasma spheroidization treatment to obtain a TaNbTiZr refractory high entropy alloy spherical powder; The temperature of the first hydrogenation treatment is 550-600°C, and the time of the first hydrogenation treatment is 2-4 hours; during the first hydrogenation treatment, the flow rate of hydrogen introduced is 1-5 L / min; The dehydrogenation treatment is carried out in a vacuum environment, the temperature of the dehydrogenation treatment is 800-850° C., the time of the dehydrogenation treatment is 2-4 hours, and the vacuum degree is ≤0.05 Pa; The temperature of the second hydrogenation treatment is 550-600° C., and the time of the second hydrogenation treatment is 2-4 hours. During the second hydrogenation treatment, the flow rate of the hydrogen introduced is 1-5 L / min.

2. The method for preparing a TaNbTiZr refractory high entropy alloy spherical powder according to claim 1, characterized in that: The purity of Ta, Ti, Nb and Zr is ≥99.9%; Ta and Ti are subjected to vacuum arc melting for 3 to 5 times to obtain TaTi master alloy, Nb and Zr are subjected to vacuum arc melting for 3 to 5 times to obtain NbZr master alloy, and TaTi master alloy and NbZr master alloy are subjected to vacuum arc melting for 3 to 5 times to obtain TaNbTiZr refractory high entropy alloy ingot.

3. The method for preparing a TaNbTiZr refractory high entropy alloy spherical powder according to claim 1, characterized in that: The rotation speed of the ball milling treatment is 200-300 rpm, the time of the ball milling treatment is 5-20 h, and the ball-to-material ratio is (5-10):

1.

4. The method for preparing a TaNbTiZr refractory high entropy alloy spherical powder according to claim 1 or 3, characterized in that: During the ball milling process, the materials of the ball milling jar and the grinding balls are both hard alloy.

5. The method for preparing a TaNbTiZr refractory high entropy alloy spherical powder according to claim 1, characterized in that: The particle size of the refractory high entropy alloy hydride particles is less than 100 meshes.

6. The method for preparing a TaNbTiZr refractory high entropy alloy spherical powder according to claim 1, characterized in that: The process parameters of the plasma spheroidization are: a carrier gas flow rate of 40 to 60 slm, a center gas flow rate of 30 to 40 slm, and a sheath gas flow rate of 60 to 80 slm, wherein the carrier gas, the center gas, and the sheath gas all use argon with a purity of ≥99.999%, the plasma power is 12 to 15 Kw, the reaction chamber pressure is 7.5 to 15 psia, and the powder feeding rate is 5 to 10 g / min.

7. The TaNbTiZr refractory high entropy alloy spherical powder prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The TaNbTiZr refractory high entropy alloy spherical powder has a BCC single-phase structure, a powder particle size of 30-150 μm, and a powder sphericity of ≥0.95.

Images