Formation mechanism of cobalt-gradient structure in WC-Co hard alloy

The formation method of cobalt-gradient structure in WC-Co hard alloy with a two-step sintering process and its effects were discussed. It was observed that the thickness of the gradient layer increased with an increase in the gross carbon content and with a decrease in the carbuizing temperature. Cemented carbides with a Co gradient which composed of WC-rich surface, a Co-rich middle layer and an ηphase containing core were achieved by a two-step sintering process. Result shows that a higher carbon content led to finer η phase, and the retention of more cobalt liquid.