Strain-rate dependence of the compressive strength of WC–Co hard metals

Abstract

The strain-rate dependence of WC–Co hard metals with binder contents of 6, 8, 10 and 12wt% was investigated. The materials were processed by spark plasma sintering and exhibited WC grain sizes of about 200nm. Static compressive strength was investigated using a servo-hydraulic testing machine. Dynamic compression tests were performed in an instrumented drop-weight tester as well as a modified Split–Hopkinson pressure bar (MSHPB). The compressive strength of the cylindrical test specimens increased with decreasing Co content and increasing strain rate, from 4370MPa for WC–12Co under quasi-static loading to 6660MPa for WC–6Co under dynamic loading.For the evaluation of the fracture mechanisms, the fragment size of the broken parts was determined by optical particle analysis. The results indicated an increase in microcrack density with increasing strain rate.Based on the findings, different model curves were fitted to the experimental data to describe the strain-rate dependent compressive strength with respect to Co content.