Rearrangement and pore size evolution during WC-Co sintering below the eutectic temperature

The early stage densification during sintering of a WC-Co material has been investigated using image analysis to obtain pore size distributions of partially sintered samples. Sintering shrinkage is related to rearrangement of the WC particles. A bimodal pore size distribution develops during isothermal holding, but not during heating. A given isothermal holding results in less densification after slow heating than after fast heating. It is suggested that isothermal holding yields a more rigid compact when the equilibrium solubility is approached, and that the thermal expansion anisotropy of the WC-Co system plays a role during heating. Rearrangement was simulated with a discrete element method. The simulations suggest that microstructure evolution retards significantly as isothermal conditions are established. Attempts to introduce dissolution in the simulations failed to represent the expected increase in density.