Abstract
Peculiar fracture sources and related surface structures formed around fracture sources in WC-Co, WC-TiC(TaC)-Co and WC-VC-Co alloys were examined by scanning electron micrography.
It was found that: (1) In a WC-Co alloy, a flat region or a stepped region appearing around the carbide defects with the size less than about 8, um, would closely be related to the domain (or grain) bounda-ry of binder phase. The stepped region formed in high cobalt alloys seems to lower the strength of the alloy. (2) In a WC-TiC(TaC)-Co alloy, a stepped defect formed by the addition of a small amount of TiC(TaC) is found to be a sort of pore with irregular shape. (3) In an ultra fine grained WC-VC-Co alloy, a peculiar source would be a region having densely distributed micropores.
