Investigation on reduction and carbonization process of WC-Co composite powder obtained by In situ synthesis

Abstract

WC-Co composite powders with WC grain size of about 170 nm were synthesized by spray conversion process and in situ synthesis at 1173 K, which is much lower than the traditional carbonization temperature. The reaction process of in situ synthesis process was investigated by thermodynamic calculation, XRD, XPS, SEM and TEM. Based on the results of thermodynamic calculation, XRD and XPS, it is found that Co3O4 is firstly reduced to CoO, which is further reduced to Co. WO3 is also reduced to low valent tungsten oxide firstly in the range of low temperature, and then reduced to W at higher temperature. In addition, the effects of synthetic temperature on the phase and morphology of composite powders were investigated systematically in the range of 873 K–1273 K. The thermodynamic analysis and experimental verification results obtained in the present work are significant to control and optimize the preparation processes of in situ synthesizing WC-Co composite powder.