Preparation of WC-MoC Ceramics and their Mechanical Properties

Abstract

Ceramics composed of (W, Mo)C were prepared by reaction sintering WC-Mo₂C-C powder mixtures at 1700°C using resistance-heated hot-pressing in which the solid-state reaction (1-x)WC+x/2Mo₂C+x/2C→W_1-xMo_xC (x=0.05-0.40) occurred. The ceramics were then annealed at 2000°C. The hot-pressed and annealed ceramics were characterized by density, microstructure, and mechanical properties. Unreacted Mo₂C remained in the ceramics before annealing; after annealing, the ceramics with x<0.2 were composed of W_1-xMo_xC. The solid-solution phase in each grain was not compositionally homogeneous, being separated into two phases of W-rich and W-poor regions. For the ceramics with x<0.2, Young's modulus decreased a little with x, and the Vickers hardness was almost constant. The fracture toughness did not show a significant dependence on x.