Characteristics and Microstructure Evolution of Spherical NbMoTaWZr-HfC Powders Fabricated by Spray Granulation Combined with Plasma Spheroidization

NbMoTaWZr-HfC spherical powder was fabricated by spray granulation combined with radio frequency plasma spheroidization. The macroscopic characteristics, phase composition and microstructure of the powder are studied. The results reveal that the composite powder is spherical and the particle size ranges from 13.31 mu m to 32.11 mu m with D-50=19.62 mu m. The sphericity, flow rate and bulk density of the spheroidized powder are 0.98, 0.198 s/g, 7.20 g/cm(3). Moreover, the main phases of NbMoTaWZr-HfC spherical powder are body-centered-cubic (bcc) solid solution+ZrO2+HfC phase and it has dendritic and cellular structure. The element distribution in the spherical NbMoTaWZr-HfC powder is uniform. However elemental segregation occurs in the dendritic scale region; high melting point elements such as W, Mo, and Ta are enriched in the dendrite arm, low melting point elements such as Nb and Zr are enriched at the interdendritic region, and the Hf are uniformly distributed.