Sintering shrinkage of WC-Co materials with bimodal grain size distributions

Sintering shrinkage and densification rate were investigated for WC-Co materials with different grain size distributions. Unimodal distributions were compared to bimodal mixtures with size ratio close to four. A bimodal carbide mixture with 25% fine particles showed similar shrinkage behaviour to a material with unimodal distribution around the same mean value. With 50% fine particles the initial shrinkage was slightly faster than a unimodal material with the same mean size, while the late shrinkage was considerably slower. The effects of particle size distribution on particle packing and sintering are discussed, and the effect on viscosity modelled.