Preparation ultrafine WC based on the new tungsten metallurgy system of “no ammonia transformation - no hydrogen reduction”

Abstract

The preparation of ultra-fine tungsten carbide (WC) is a difficult and hot topic in tungsten industry. The industrial production process requires the need to transform tungsten concentrates to produce ammonium paratungstate (APT) intermediate products followed by hydrogen reduction to produce W, and finally carburization to produce WC. Due to the formation of H2O in the hydrogen reduction process, it is difficult to obtain <100 nm tungsten powder materials. Therefore, in this study, a novel method was introduced that synthesizes ultrafine WC via hydrothermal synthesis of ZnWO4 followed by a carbothermic reduction–carburization process. The findings of this study showed that ZnWO4 with a particle size of 29 nm was synthesized from Na2WO4 solution. This can solve the problem of ammonia‑nitrogen wastewater discharge in the process of APT preparation, and prepare nano-scale raw material. In addition, zinc is volatile at high temperature, which has been widely used in the field of recycling waste cemented carbide. Based on this, the WC mixed powder was obtained by carbothermic reduction of ZnWO4 under the condition of excess C addition, which can inhibit the agglomeration of particles and avoid the production of H2O. Then the single-phase WC with a particle size of 60 nm was obtained by a carburization reaction process at 1300 °C for 3 h. The research intersects tungsten metallurgy with tungsten material preparation, shortens the production process and reduces waste water discharge.