Production of WC Powder from WO₃ Added Co₃O₄

Abstract

A process for production of fine WC powders using Co₃O₄ as an additive was investigated. The mixed powder of WO₃, carbon black and 0.4 to 6.25%Co₃O₄ was reduced and carburized in H₂ at various temperatures. This report deals with the result of the examination on the operating conditions and the particle size of the obtained WC.
From the chemical analysis of combined carbon contents of the products and identification of the compounds by X-ray analysis, it was found that the mixed powder containing more than 1.6%Co₃O₄ could be carburized at 900°C. When the Co₃O₄ content is less than 1.6%, the lower the Co₃O₄ content the higher the carburization temprature, and the effect of Co addition was almost negligible at less than 0.4%Co₃O₄. The WC particle size obtained became coarser as the degree of reduction, carburization temperature and Co₃O₄ content increased. The particle size of more than about 0.6 μm could be controlled by regulating these three factors. Although in this process the WC was carburized at a much lower temperature than in the usual process, where WC was prepared by the reaction between W and C, its grain size of WC determined by X-ray diffraction was comparatively large and became larger with increasing Co₃O₄ content of the mixed powder.