The influence of stress state on the compressive strength of WC-Co with different Co contents

The stress-state dependence of WC-Co hard metals with binder contents of 6 and 12 wt.% was investigated. The materials, which were free of grain growth inhibitors, were consolidated by spark plasma sintering and exhibited WC grain sizes of about 200 nm. Quasi-static compression tests, which were performed in a servo-hydraulic testing device on cylindrical test samples with and without confining pressure, demonstrated an increase in fracture strength due to the multiaxial stress state. The compressive strength of the WC-6Co exhibited an increase of 20% when a confining pressure of 4% of the initial compressive strength was applied. In a similar fashion, the compressive strength of the WC-12Co increased by 22% under an applied confining pressure of 4.8% of the materials' initial compressive strength. An optical evaluation of the damage in the confined samples showed that these samples didn't fragment completely, as would normally have occurred under compressive loading without radial pressure. Energy dissipation occurred through the formation of crack bridges in WC-12Co and the generation of crack networks in both material configurations.