Effect of WC particle size on Co distribution in liquid-phase-sintered functionally graded WC-Co composite

Functionally graded WC-Co materials can be manufactured by controlling liquid phase migration or liquid redistribution during liquid phase sintering. The driving force of liquid phase migration is liquid migration pressure Pm which depends on the solid particle size d and the liquid phase volume fraction u. In this study, the effect of d on Pm has been studied experimentally for WC-Co system. The results show that Pm is proportional to 1/d0.4 which is different from previous postulation that Pm is proportional to 1/d. The reason for this difference is that the previous postulation was based on the assumption that all the solid particles in a composite are mono-sized and isometric-shaped, while in real WC-Co composites WC particles usually have non-isometric shape and there is a wide particle size distribution. The dependence of Pm on both d and u has been quantitatively established, enabling the prediction of final Co composition gradient in liquid-phase-sintered WC-Co composites.