Optimizing the synthesis of ultrafine tungsten carbide powders by effective combinations of carbon sources and atmospheres

• Published in: International journal of refractory metals & hard materials Vol. 63; pp. 9 - 16
• Main Authors: Oro, R., Hryha, E., Gilardi, R., Alzati, L., Nyborg, L.
• Format: Journal Article
• Language: English
• Published: Shrewsbury Elsevier Ltd 01.02.2017; Elsevier BV
• Subjects: Activation; Agglomeration; Atmospheres; Carbides; Carbon; Carbon black; Carbon sources; Carbothermal reduction; Gas-solid reactions; Grain growth; Graphite; Mechanical and thermal activation; Metal/oxide-carbon-atmosphere interaction; Microstructure; Precursors; Sintering; Synthesis; Tungsten; Tungsten carbide; Tungsten oxides; WC-powder synthesis; Mechanical and thermal activation; WC-powder synthesis; Carbothermal reduction; Metal/oxide-carbon-atmosphere interaction; Carbon sources
• ISSN: 0263-4368; 2213-3917; 2213-3917
• DOI: 10.1016/j.ijrmhm.2016.04.012

Nanostructured WC powders can provide technologically attractive properties due to the fine microstructures obtained after sintering. Either W or WO3 powders are used for the industrial production of WC. In both cases, the contact area between carbon and tungsten precursors has a critical influence on the reaction temperatures, which in turn affects grain growth and agglomeration of particles. Different methods have been studied to increase the reaction rates by enhancing the contact between reactants: carbon coating of tungsten powder, solid-gas reactions of tungsten powders with atmospheres containing CH4, or mechanical activation followed by thermal activation of tungsten and carbon precursors. In this work WC-powders were obtained by mechanical activation of tungsten and carbon precursors followed by thermal activation of these mixes at temperatures up to 1100°C. A systematic study has been carried out combining two dissimilar carbon sources (graphite and carbon black), with different atmosphere compositions (Ar, Ar-50H2, Ar-10CO) and studying the evolution of phases at different stages of the synthesis. The results show how the efficiency of the interaction between carbon sources and atmospheres affects the completion of the synthesis. The synthesis of WC from WO3 in H2 containing atmospheres is enhanced when using carbon black sources, however in CO containing atmospheres the most effective interaction is with graphite. •Synthesis of WC-powder by mechanical and thermal activation with W or WO3 sources•Study the effect of the interaction with different carbon sources and atmospheres•Synthesis of submicron WC powders achieved at 1100°C•Additions of CO to inert atmospheres assess the reduction/carburization process•Interaction of CO atmospheres more efficient with graphite than with carbon black