LAUSR

Abstract Effect of calcium on tungsten oxide, tungsten, tungsten carbide and WC-Co cemented carbides, and the evolution of Ca during the preparation of cemented carbides were investigated studied by the liquid-solid doping method. X-ray diffraction, scanning electron microscopy and transmission electron microscopy were employed to analyze the phase compositions, particle sizes and morphologies of them, respectively. The results showed that 1% Ca-doped tungsten oxide consisted of WO3 and CaWO4 phases. After hydrogen reduction, the size of Ca-doped tungsten decreased slightly. During carbonization, most of the CaWO4 and Ca4.26W10O30 transformed to CaC2. After that, the majority rest of the CaWO4 and Ca4.26W10O30 both reduced to CaO in the sintering process. The microhardness, flexural strength and fracture toughness of 1%Ca-doped WC-6wt.%Co cemented carbide were 14.83 GPa, 1456 MPa and 9.98 MPa m1/2, decrement of 10.12%, 29.53%, and 10.57%, respectively. A refining mechanism for tungsten and a weakening mechanism for WC-Co cemented carbides were proposed.