Synthesis of Spherical V-Nb-Mo-Ta-W High-Entropy Alloy Powder Using Hydrogen Embrittlement and Spheroidization by Thermal Plasma

Abstract

V-Nb-Mo-Ta-W high-entropy alloy (HEA), one of the refractory HEAs, is considered as a next-generation structural material for ultra-high temperature uses. Refractory HEAs have low castability and machinability due to their high melting temperature and low thermal conductivity. Thus, powder metallurgy becomes a promising method for fabricating components with refractory HEAs. Therefore, in this study, we fabricated spherical V-Nb-Mo-Ta-W HEA powder using hydrogen embrittlement and spheroidization by thermal plasma. The HEA ingot was prepared by vacuum arc melting and revealed to have a single body-centered cubic phase. Hydrogen embrittlement which could be achieved by annealing in a hydrogen atmosphere was introduced to get the ingot pulverized easily to a fine powder having an angular shape. Then, the powder was annealed in a vacuum atmosphere to eliminate the hydrogen from the hydrogenated HEA, resulting in a decrease in the hydrogen concentration from 0.1033 wt% to 0.0003 wt%. The angular shape of the HEA powder was turned into a spherical one by inductively-coupled thermal plasma, allowing to fabricate spherical V-Nb-Mo-Ta-W HEA powder with a d50 value of 28.0 μm.