A new 0.4 mu m WC powder as well as powder-related properties and sintering behaviour of 0.6 to 30 mu m WC-Co hardmetals

A new 0.4 mu m WC powder with hardmetal properties based on optimized structures and doping additives obtained by sintering is presented. The HV30 hardness of hardmetals made from this new DS 40 powder with 10 wt-% Co extends up to 2000 and a hardness of 1870 can be combined with a PALMQVIST toughness of 810 N/mm or 10.5 MPam1/2. Connections between powder, structure, and hardmetal properties are established and discussed for the entire range of WC grain sizes commercially available. Some extrapolations are made to predict properties of hardmetals with ultrafine and nanophased structures to be developed in the near future. As shown by thermoanalytical investigations, solid-state sintering contributes more than 75 % toward the total densification of WC-Co hardmetals and strongly depends on properties and processing of the starting powder, doping and WC grain size. A model of that solid-state sintering prior to the binder melting is proposed.