The Palmqvist indentation toughness (W) has been determined for a series of WC-Co hardmetals containing up to 10 wt % cobalt. Using a correlative parameter (the cobalt mean-free path) the Palmqvist toughness has been compared with true fracture toughness data (GIC values) for similar materials, obtained by conventional testing techniques. It has been shown that a linear relationship between W and GIC can be predicted, on the basis of a recent theory of the fracture process in hardmetals. The validity of such a relationship has been experimentally confirmed, over a limited range of hardmetal compositions and microstructures. The experimental difficulties and expense associated with fracture toughness determination for brittle materials such as hardmetals, by quasi-conventional techniques, are well known. It is concluded that the Palmqvist test provides a useful method of measuring fracture toughness on a routine basis, since it is simple to perform, non-destructive, and does not require a specialized testpiece geometry. Its application in hardmetal quality control is, therefore, indicated. © 1979 Chapman and Hall Ltd.
