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

Abstract

Abstract WC–(10, 20, 30, 40, 50) vol.%Al 2 O 3 composites were consolidated by high energy ball milling and the following hot-pressing sintering method. The tungsten carbide (WC) and commercial alumina (Al 2 O 3 ) powders composed of amorphous Al 2 O 3 , boehmite (AlOOH) and χ-Al 2 O 3 were used as the starting materials. The effects of the commercial Al 2 O 3 content on the density, microstructure and mechanical properties of WC–Al 2 O 3 composites were investigated. The results showed that the Al 2 O 3 content had remarkable influence on the microstructure, crack propagation path and mechanical properties of WC–Al 2 O 3 composites, the fracture of the composites was a mix of intergranular and transgranular fracture. With the increasing content of Al 2 O 3 , 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.%Al 2 O 3 composite. When the as milled WC–40 vol.%Al 2 O 3 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 m 1/2 with an acceptable flexural strength of 756.3 MPa.