Preparation and characterization of ZrB₂/SiC composite powders by induction plasma spheroidization technology

In this work, ZrB₂/SiC powders were synthesized by spray drying and induction plasma spheroidization (IPS) process. Compared with loose and fragile agglomerated powders, the flowability and apparent density of the ZrB₂/SiC powders was markedly improved because micro-defects in the powders were reduced after IPS process. Powder sizes and process parameters have an important impact on the interaction between powder and plasma and thus further affect the spheroidization effect of the powder. Based on orthogonal experiment design, the sequence of the IPS process parameters according to their degree of influence on the sintering rate, from strong to weak, was the powder feed rate, the sheath gas flow, the chamber pressure and the central gas flow. The optimal parameters to improve the sintering rate of the ZrB₂/SiC powders were a powder feed rate of 6 rpm, a sheath gas (H₂) flow of 9 slpm, a chamber pressure of 12 psig and a central gas (Ar) flow of 90 slpm. The sintering rate of the optimized powders was improved to 70.5%, the flowability was 48.4 s/50 g, and the apparent density was 1.92 g/cm³.