Discussion of Nonconventional Effects in Solid-State Sintering of Cemented Carbides

WC–Co materials are usually produced through a powder metallurgy route, including a liquid-phase sintering step in the 1350°–1450°C temperature range. However, it is well established that a large part of sintering already occurs in the solid-state for micrometer or submicrometer WC particles. Solid-state spreading of the Co-rich binder phase and local rearrangement of WC particles are responsible for the compact densification. But important issues still remain unexplained. First, densification by pure rearrangement should stop at a critical packing fraction of the WC refractory phase. Second, a strong influence of the C/W ratio on the spreading and sintering kinetics is observed experimentally. Both these effects are discussed in this paper, based on experimental dilatometric results, microstructural investigations by SEM and transmission electron microscopy, and considerations about interfacial energies in the system.