Kinetics of cobalt gradient formation during liquid-phase sintering of functionally graded WC-Co

Carbon is a critical element that can be used to produce a cobalt gradient in WC-Co composites. The cobalt gradient formed during liquid-phase sintering of WC-Co involves migration of the liquid phase, diffusion of carbon in the liquid phase, and reaction of carbon with W3Co3C phase particles. The graded microstructure produced in this study exploited the kinetic process of carbon diffusion and the phase reaction of carbon with eta phase (Co3W3C) and is a non-equilibrium or metastable microstructure, Thus, the graded microstructure is a function of time at the sintering temperature, as well as other factors, and a study of the kinetics of the process is therefore necessary to fully understand the process and control the microstructure. This study assessed the effect of carbon gradient and holding time at the sintering temperature on the overall kinetics of the process.