In-situ preparation of WC-Co composite powders

WC-6Co and WC-10Co composite powders with uniform distribution of Co phase were successfully prepared using WO3, Co2O3 and carbon black as raw materials by the process of "carbothermal pre-reduction + solid phase carbonization". The phase evolution as well as the influences of carburizing time and temperature on the morphology and particle size of products were investigated. The results showed that there were two reduction paths for WO3. In one case, the reduction of WO3 was completed in the order of WO3 -> W 18 O 49 -> WO2 -> W and W2C. The other was that WO3 first reacted with Co3O4 to form CoWO4, and then CoWO4 was directly reduced to W and W2C. Combined with the thermodynamic calculation and XRD results, W and W2C preferentially transformed into low-carbon eta phase (Co3W9C4 and Co2W4C) rather than WC phase. Subsequently, Co3W9C4 and Co2W4C were transformed into Co3W3C. Finally, the Co3W3C phase was further carbonized to form WC and Co phases. Moreover, the increase of Co content promoted the reduction and carbonization reactions. The morphology and particle size had little change with the extension of carburizing time. However, as the carburizing temperature rose, the particle size of WC increased obviously, and there was a serious agglomeration.