Preparation of nano-scaled WC powder by low-temperature carbothermic reduction method

Abstract

Nano-scaled WC powder is an important material for preparation of ultrafine or nano-grained WC-based cemented carbides via powder sintering method. In this paper, nano-scaled WC powder was prepared based on traditional carbothermic reduction method. First, the mixture of WO3 and carbon were reacted at 1000 °C to remove all the oxygen atom. Then, according to residual carbon content in the deoxidation products, the gas-phase (by 90%H2 + 10%CH4, at 900 °C) or solid-phase carburizing process (at 1100 °C) was selected to prepare WC powder, respectively. The results indicated that the use of nano carbon black in first stage could provide a large number of dispersed nuclei, and meanwhile, a low reaction temperature was beneficial to inhibit the growth of product particles. The thermodynamic calculation, reaction behavior and nuclei growth behavior in deoxidation and carbonization stages were studied in detail. As the C/WO3 ratio was 2.5 and 3.8, the WC powder with total carbon content of 6.23% and 6.19%, particle size of 80.29 nm and 95.24 nm, and BET value of 3.88 m2/g and 4.25 m2/g was obtained by this method, respectively.