Refined WC grain size and improved mechanical properties in a hardmetal WC-8Co processed via short-time semi-solid hot pressing

Abstract To minimize WC grain growth and avoid WC-WC non-metallurgical contacts in WC-Co hardmetals, we modified conventional solid-state hot pressing into short-time semi-solid hot pressing (STSSHP) for consolidation of WC-Co powders in the present study. STSSHP can produce fully dense WC-Co hardmetals free of WC-WC non-metallurgical contacts at semi-solid temperatures lower than the ideal liquid-phase sintering temperatures within several to several ten seconds, thus minimizing WC grain growth. Herein WC-8 wt%Co processed by STSSHP at 1340 ℃ (the WC-Co eutectic temperature) for only ~15 s achieved a relative density of 99.92% without WC-WC non-metallurgical contacts. Only slight WC grain growth occurred during STSSHP relative to grain sizes in powders. The STSSHP-ed WC-8 wt%Co exhibited much smaller WC grains and thus higher hardness, fracture toughness and bend strength than those in its liquid-phase sintered counterparts. STSSHP provides a novel avenue to retain fine WC grains and hence to improve both hardness and ductility of WC-Co hardmetals.