Recycling of WC-Co hardmetals by oxidation and carbothermal reduction in combination with reactive sintering

Abstract

A novel recycling technology for the production of bulk WC-Co hardmetals from a mixture of WO 3, CoWO 4 and graphite powders by way of carbothermal reduction in combination with reactive sintering has been developed. Waste hardmetals parts with 15 wt% Co from hardmetals production were fully oxidized into a mixture of WO 3 and CoWO 4 powder. To oxide powder mixtures, carbon was added in the form of nanocrystalline graphite, milled, pressed into compacts and sintered. During reactive sintering carbothermal reduction, tungsten monocarbide (WC) synthesis and structure formation occurs in one cycle. The influence of different graphite content in the initial powder mixtures on the phase composition, and linear shrinkage during solid and liquid state sintering is discussed. The microstructure of reactive sintered WC-Co composites is fine-grained and identical to that of the original WC-Co microstructure and has similar mechanical properties.