Formation of Co-capping during sintering of straight WC-10Â wt% Co

Co-capping is a term that refers to a thin layer of Co occasionally observed on the surface of sintered WC-Co parts. It is usually considered undesirable and needs to be removed. The mechanism of its formation has been a myth in the industry and not fully understood to date. In this study, the effects of several factors, including cooling rate, atmosphere and carbon content in specimens, on the formation of Co-capping during sintering of straight WC-Co materials were experimentally examined. The mechanism of Co-capping formation was discussed based on the principles of liquid-phase migration.