Microstructure and mechanical properties of hot-pressing sintered WC–x vol.%Al2O3 composites

WC–(10, 20, 30, 40, 50) vol.%Al2O3 composites were consolidated by high energy ball milling and the following hot-pressing sintering method. The tungsten carbide (WC) and commercial alumina (Al2O3) powders composed of amorphous Al2O3, boehmite (AlOOH) and χ-Al2O3 were used as the starting materials. The effects of the commercial Al2O3 content on the density, microstructure and mechanical properties of WC–Al2O3 composites were investigated. The results showed that the Al2O3 content had remarkable influence on the microstructure, crack propagation path and mechanical properties of WC–Al2O3 composites, the fracture of the composites was a mix of intergranular and transgranular fracture. With the increasing content of Al2O3, the relative density increase, while Vickers hardness and fracture toughness increased initially to the maximum values and then decreased. The optimum flexural strength of 949.32 MPa is obtained in the WC–20 vol.%Al2O3 composite. When the as milled WC–40 vol.%Al2O3 powders were hot-pressing sintered at 1540 °C for 90 min, a relative density of 97.98% with an excellent Vickers hardness of 18.65 GPa was achieved, combining a fracture toughness of 10.43 MPa m1/2 with an acceptable flexural strength of 756.3 MPa.