A facile pathway to prepare ultrafine WC powder via a carbothermic pre-reduction followed by carbonization with CH4-H2 mixed gases

In the present work, ultrafine tungsten carbide (WC) powder with a high purity has been prepared by first roasting yellow tungsten trioxide (WO₃) and carbon black powder under argon atmosphere followed by the further carbonization reaction with CH₄-H₂ mixed gases. The effects of C/WO₃ molar ratio, CH₄ percentage in the CH₄-H₂ mixed gases on the phase composition, morphology and particle size of the products were discussed. The results revealed that when the C/WO₃ molar ratios were 2.5 and 2.6, nano tungsten carbide powder with the average particle sizes of 93 nm and 77 nm could be prepared. Whereas, when the C/WO₃ molar ratio was in the range of 2.7–3.5, the finally prepared WC has the particle size of 446–192 nm, and became smaller with the increase of C/WO₃ molar ratio. The percentage of CH₄ should be <15% to prepare WC with a low free carbon content. From the results of thermodynamic calculation, X-ray diffraction (XRD), FE-SEM, and infrared carbon‑sulfur analyzer, it was concluded that ultrafine tungsten carbide powders with a high purity could be successfully prepared by this method.