Fabrication of ultrafine and high-purity tungsten carbide powders via a carbothermic reduction-carburization process

In the current study, ultrafine and high-purity tungsten carbide (WC) powders are successfully prepared by a two-step process: carbothermic reduction of WO3 followed by carbonization reaction. The effects of the C/WO3 molar ratio, reaction temperature and reaction time on the phase transition and morphology evolution of the products are investigated. During the carbothermic reduction process, all the oxygen in yellow tungsten trioxide (WO3) is removed by carbon to generate a mixture of W, W2C and WC at 1100 degrees C; and then the as-prepared powder is mixed with an appropriate content of carbon black and carbonized at 1200 degrees C. The carbon content in the finally obtained WC powders is almost equal to the theoretical value. Furthermore, it is found that a high C/WO3 molar ratio at the first stage is beneficial for decreasing the particle size of the WC powders. When the C/WO3 molar ratio is 3.5, the single phase WC with a particle size of about 200 nm can be obtained. Therefore, this carbothermic reduction -carburization process may provide a simple, low-cost, and high efficiency route to prepare the WC powders in a large-scale. (C) 2019 Elsevier B.V. All rights reserved.