Shock response of cobalt-based tungsten carbide cermet

Cemented tungsten carbides are metal matrix composites in which a large fraction of hard tungsten carbide (WC) grains are embedded in a soft transition metal matrix, e.g., cobalt, nickel, iron, etc., commonly referred to as the binder. Because of their high density and hardness, these composites have been particularly attractive in applications where high-rate mechanical loading, high hardness, and high wear resistance is important. In the present study, shock wave experiments are conducted to better understand the structure of shock waves and their associated thermodynamic states in shock-compressed cemented WC with 3 wt. percent Co binder. The peak shocked state of interest to this study is up to 90 GPa, which is more than ten times the Hugoniot Elastic Limit reported for WC ceramics in the literature. The measured wave profiles indicate the cermet to undergo elastic-plastic deformation during its shock compression. A three-stage particle velocity profile is observed in the experiments -- an initial elastic-rise to the (HEL), an elastic-plastic ramp indicating substantial post-yield hardening, and finally a rise to the peak shocked Hugoniot state. Besides calculation of in-material quantities in the elastic-limit and the peak shocked Hugoniot states, Hugoniot relations for the WC sample in terms of the shock velocity vs. particle velocity and longitudinal stress vs specific volume are determined over the stress range of interest. The results indicate the WC cermet samples to preserve substantial shear strength in the post-yield deformation regime up to 90 GPa.  No phase transformation was observed up to 90 GPa.