FRACTURE STRENGTH BEHAVIOR OF TOOL CARBIDES SUBJECTED TO THERMAL SHOCK.

A generalized theory for the retained strength of brittle ceramics after severe thermal shocks has been presented by Hasselman, which predicts a discontinuity in retained strength at some critical quenching temperature difference ( DELTA T//c). Such strength behavior has been experimentally verified by several workers for Al//2O//3 and ZnO. The present note discusses the fracture strength behaviors of two different tool carbides, WC and a TiC, subjected to severe thermal shocks. While the TiC shows results in good agreement with Hasselman's model, the WC does not exhibit instantaneous strength loss over the range of quenching temperatures studied. The results reported here suggest that the WC should be a better cutting tool in view of its higher resistance to crack initiation and its better strength behavior with increasing thermal shock severity.