[SIS9] Hard Materials

[16F-SIS9-03] Liquid Phase Migration and Shape Distortion of WC-Co Cemented Carbides during Sintering -The Effect of Temperature Gradient in Sintered Compacts during Cooling-

*T. Saito¹, H. Matsubara², Y. Fukuichi¹, T. Kajiwara¹, H. Endo¹, S. Terasaka^2,3 (1.Kyoritsu Gokin Co., Ltd. , Japan, 2.Tohoku University Graduate School of Environmental Studies, Japan, 3.Japan Fine Ceramics Center, Japan)

Keywords:cemented carbides, liquid phase sintering, shape distortion, migration pressure, Co solid-liquid coexistence region

WC-Co cemented carbides (alloys) sometimes exhibit unpredictable shape distortion during sintering. We investigated the shape distortion of WC-Co alloys during sintering focusing on the liquid phase migration (LPM) and the temperature gradients that arise within the alloys. As a result, we found that during cooling after sintering, an inevitable temperature gradient is generated in the alloys, and the LPM occurs from the high temperature region to the low temperature region, resulting in the shape distortion. The faster the cooling rate, the larger the distortion. It was also found that the liquid phase migrates from the Co liquid phase region toward the Co solid-liquid coexistence region. We have concluded that this LPM is caused by the migration pressure occurring in the Co solid-liquid coexistence region, which we have named PSL. PSL should be generated because FWC/Co(S) derived from gWC/Co(S) and gCo(L)/Co(S) is higher than FWC/Co(L) derived from gWC/Co(L).