Toughening cemented carbides by phase transformation of zirconia

Abstract

Yttria partially stabilized zirconia was introduced into WC-Co cemented carbides to enhance their mechanical performance. The hardness and fracture toughness were improved simultaneously with the addition of ZrO2. Particularly, the fracture toughness of the cemented carbides was significantly enhanced. The mechanism was mainly attributed to the stress-induced phase transformation of tetragonal ZrO2 to monoclinic ZrO2. This phase transformation introduced a compressive stress field and deflected the micro-cracks. In addition, the ZrO2 particles dispersed homogeneously in the WC skeleton and had good interfacial bonding with both WC and Co phases, which was beneficial to the mechanical properties of the cemented carbides. This study provides a new promising approach to break the trade-off between the hardness and fracture toughness of cemented carbides to achieve excellent comprehensive mechanical properties. The new strategy will be also promising to be applied in a variety of cermets or ceramic-based composites.

Keywords

• Cemented carbide
• Stress-induced phase transformation
• Toughening
• Zirconia