Microstructural Development and Properties of New WC-Co Base Hardmetal Prepared From CoxWyCz + C Instead of WC.

Abstract

We had already reported that WC-Co base hardmetal (W+Graphite+Co alloy) prepared from W+Graphite mixed powder instead of conventional WC powder has a large amount of highly oriented plate-like triangular prismatic WC crystal grains, and that both fracture toughness and transverse-rupture strength are higher than those of the conventional hardmetals at an identical hardness. In this study, we prepared another new WC-Co base hardmetal by using Co, W, C, complex carbide such as CO3W9C4 (K) and Co2W4C (θ) as the main starting material. It was clarified that WC crystal grains in the new hardmetal are also plate-like triangular prismatic, but are not oriented, differing from W+Graphite+Co alloy. The fracture toughness, however, was higher by 10-15% than that of the conventional alloy at an identical hardness, while the transverse-rupture strength was comparable with that of the conventional alloy.