Fabrication of ZrB2-SiC powder with a eutectic phase for sintering or plasma spraying

Abstract

Spherical ZrB2-SiC powder with a eutectic phase was synthesised via induction plasma spheroidisation (IPS) in this study. The influence of H2 flow and reaction chamber pressure on the powder microstructure was investigated during the induction plasma spheroidisation process. The powders have an evidently better fluidity (< 44 s/50 g) and a larger apparent density (>1.65 g/cm3) after IPS treatment. With an increase in H2 flow or pressure, the shape of surface grains successively shows an irregular, hexagonal, and rectangular shape because the grain growth mechanism changes from surface energy to diffusion activation energy. There is serious mass loss of SiC on the surface because of pure active oxidation and sublimation during the IPS treatment. The cross section of the ZrB2-SiC powder indicates a dense microstructure comprising coarse ZrB2 and intergranular eutectic phases. Furthermore, the corresponding ZrB2-SiC bulk ceramics and coating fabricated using the IPS-treated powder both contain eutectic phase.