K_Ic-values of tungsten carbide-cobalt (WC-Co) hard metals were measured using the short-rod (chevron-notched) specimen geometry. Nine alloys of various cobalt contents and tungsten carbide particle sizes were tested using modified self-aligning tensile grips. A compliance method was adopted for the test.

For comparison, the same WC-Co alloys were tested using single-edge-notched beam (SENB) specimen geometry in four-point bending. A sharp notch was introduced into the SENB specimen using a thin copper foil blade in an electrical discharge machine (EDM).

The same alloys were also tested using Barker's flatjack method with short-rod specimen geometry.

Microstructural parameters, mean free path of cobalt, mean intercept length, and contiguity of WC, were measured using a semiautomatic image analyzing method for all the alloys. Optical, scanning electron, and transmission electron micrography were used for quantitative image analysis. From these microstructural parameters, K_Ic-values were calculated using a theoretical equation derived by Hong and Gurland.

The four independent experimental K_Ic-values for nine alloys are discussed with respect to the accuracy and convenience of each experimental measuring technique.