Influence of sintering temperature and holding time on the densification, phase transformation, microstructure and properties of hot pressing WC–40 vol.%Al2O3 composites

WC–40 vol.%Al2O3 composites were prepared by high energy ball milling followed by hot pressing. 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 phase transformation during sintering, the influence of sintering temperature and holding time on the densification, microstructure, Vickers hardness and fracture toughness and the toughening effects of WC–40 vol.%Al2O3 composites were investigated. The results showed that the amorphous Al2O3, AlOOH and χ-Al2O3 were transformed to α-Al2O3 completely during the sintering process. With the increasing sintering temperature and holding time, the relative density increased and both the Vickers hardness and fracture toughness increased initially to the maximum values and then decreased. When the as milled powders were hot pressed at 1540 °C for 90 min, a relative density of 97.98% and a maximum hardness of 18.65 GPa with an excellent fracture toughness of 10.43 MPa m1/2 of WC–40 vol.%Al2O3 composites were obtained.