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

Carbon is a critical factor that can be used to produce a gradient of cobalt content 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 exploiting the kinetic process of carbon diffusion and the phase reaction of carbon with η phase (Co3W3C) 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. A study of the kinetics of the process is therefore necessary to fully understand the process, hence control the microstructure. This paper studies the effect of carbon gradient and holding time at the sintering temperature on the overall kinetics of the process.