The growth behavior of (Ti,W)C grains with rounded shape and WC grains with faceted shape in a Co matrix was investigated to study the effect of grain shape on grain growth behavior. Samples with the composition (25TiC-75WC)-30Co (wt%) were sintered at 1450℃ for various times. During sintering, the growth behaviors of (Ti,W)C grains and WC grains were significantly different to each other. In the case of rounded (Ti,W)C grains, average grain size increased continuously with a stationary grain size distribution. The grain growth followed the well-known cube law, $(r^3-r_0^3=kt)$ ; where r is the average grain size at time t, $r_0$ the initial grain size at t=0 , and k the proportionality constant. In contrast, faceted WC grains exhibited abnormal or stagnant grain growth. While abnormal grain growth with bimodal grain size distribution occurred when the initial WC powder was fine, stagnant growth prevailed when coarse WC powder was used. These results indicate that rounded grains grow normally under a diffusion controlled process and faceted grains grow following an interfacial reaction controlled process. Consequently, grain growth behavior crucially depends on the shape of the grains.
