Repetitive Thermal Shock Of WC-Co Cemented Carbides: Assessment Of Surface Integrity Changes By Means Of Spherical Indentation

Abstract

Sudden changes in temperature are recognized to be critical service-like conditions that may drive failure in cemented carbides tools and components. From a physical viewpoint, thermal shock damage in ceramic-metal composites, such as cemented carbides, is a complex phenomenon. On the one hand, it involves introduction of residual stresses at the surface, with respect to the bulk, that may induce cracking. On the other hand, there exist deformation incompatibilities between the constitutive phases. Within this context, a fine-grained WC-Co system is subjected to sudden temperature drops in water quenching from maximum value of 570 ºC to room temperature, during five cycles. The resulting surface integrity is then assessed by spherical indentation, combined with advanced microscopy characterization. It allowed to measure the onset and evolution of quasi-plastic deformation and ring cracking for the tested conditions. These results are finally used to evaluate brittleness index changes induced by multiple thermal shocks.