Microstructure and mechanical properties of WC–Ni multiphase ceramic materials with NiCl2·6H2O as a binder

Abstract

Abstract High-density WC–Ni composite ceramics were prepared by cold isostatic pressing–vacuum pressureless sintering–hot isostatic pressing with tungsten carbide (WC) powder and NiCl2·6H2O as a binder. Results show that with an increase in the contents of Ni in the metal binder phase, the relative density of WC–Ni composite ceramics is improved, and the formation of the carbon-deficient W2C phase is reduced. There is no W2C generated in the WC–1 wt% Ni material. At high temperatures, the Ni phase changes into the liquid phase and enters between the WC particles, thereby promoting the close alignment of the WC particles. Moreover, the WC particles will be more closely aligned under their own surface tension and capillary action, thereby promoting the densification of WC–Ni composite ceramics. The WC–0.5 wt% Ni composite ceramics are fully dense and show the best comprehensive performance with a microhardness of 23.0 GPa, a fracture toughness of 5.28 MPa m1/2, and a flexural strength of 1,396.58 MPa. WC–Ni composite ceramics are mainly composed of elongated triangular prism WC particles and Ni phase. Transgranular fracture was the main fracture mode of WC–Ni multiphase ceramic materials with a small amount of intergranular fracture due to the existence of the Ni phase. Such a fracture mode can increase the flexural strength of the composite material.