Solid state sintered nanoscaled hardmetals and their properties

Hardmetals are conventionally manufactured by liquid phase sintering above 1350 °C. Due to their high surface activity, nanoscaled WC powders allow a complete densification already below 1200 °C. Extensive experiments carried out with different Co contents and grain growth inhibitors showed that a complete densification is possible between 1150 °C and 1230 °C. Here the microstructure shows a bimodal Cobalt distribution, with a thin Co layer between WC grains and a lot of small Co pools. These pools are homogenously distributed throughout the microstructure and inhibit the extension of cracks. By adjusting Co starting powders the size of these Co pools can be controlled to be around 1 μm and hardness as well as fracture toughness of these solid state sintered nanoscaled hardmetals can be enhanced. Their very fine predominant nanoscaled microstructures leads for a composition of WC-10 Co to hardness values way above 2000 HV10 units and the in a distance of 3 μm to 5 μm recurring and around 1 μm in diameter large Co pools lead to improved fracture toughness.