Enhancing hardness and toughness of WC simultaneously by dispersed ZrO 2

A novel method was proposed to achieve uniform dispersion of ZrO 2 nanoparticles in the WC matrix. The prepared WC-ZrO 2 ceramic exhibited outstanding mechanical properties with simultaneously high hardness and fracture toughness. It was disclosed that the high toughness of the present WC-ZrO 2 ceramic results from the contributions of stress-induced phase transformation from t-ZrO 2 to m-ZrO 2, the homogeneous ultrafine microstructure with coherent WC/ZrO 2 interface, and the stress release of WC in the vicinity of ZrO 2. The later two factors enhance the fracture toughness by crack deflection and crack bridging. In particular, the contribution to toughness by phase transformation of ZrO 2 is 1.9 and 2.7 times of that of the crack deflection and crack bridging, respectively. This study provides a strategy to increase toughness of ceramics greatly while keeping its high hardness.