Synthesis of ultrafine WC ceramic powders with reduced carbon content by liquid phase precursor method and the sintering behaviors

Tungsten carbide (WC) plays a crucial role as a source material in the production of cemented carbides. However, achieving precise control over the size and purity of WC powders remains challenging. In this study, we present an organic liquid phase precursor method for synthesizing ultrafine, high-purity tungsten carbide powders through carbothermal reactions. Specifically, hydroquinone serves as the carbon source and undergoes substitution reactions to bond with tungsten, leading to the formation of a molecularly dispersed W–O–C network structure. To diminish the free carbon content in WC particles, ammonium metatungstate (AMT), an auxiliary tungsten source, is homogeneously dispersed within the organic precursor solution. This allows the contained W and O elements to react with the excess carbon content, thereby reducing the free carbon content in the resulting WC powders. Following calcination at 1150 °C, the WC powders attains an average particle size of approximately 200 nm and experiences a reduction in free carbon content from 5.7 wt% to 1.1 wt%. In this way, the mechanical properties are greatly improved, with the hardness of WC block increased from 2.5 GPa to 19.3 GPa as carbon is eliminated. This study demonstrates the utilization of AMT as an effective regulating reagent for reducing the carbon content in cemented carbides, thus exhibiting potential for producing high-purity and ultrafine carbide powders.