Edge toughness of tungsten carbide based hardmetals

Edge flaking of WC-based hardmetals has been examined in detail. So-called “edge toughness”, the load at which a flake will form under load vs. displacement from the specimen edge has been correlated with more commonly used toughness parameters; Palmqvist toughness, plane strain fracture toughness (KIC) and critical strain energy release rate (GIC). KIC and GIC showed better correlations than Palmqvist, though coarser grained hardmetals, exhibiting rising R-curves, were consistently found to be outliers. It is thought that this behaviour is consistent with far more pronounced crack bridging in these materials in the edge fracture mode. Mechanical property data were complimented by SEM microscopy to examine fracture behaviour in more detail.