Hardness of hexagonal tungsten carbide crystals as a function of orientation

A new depth-sensing microhardness mapping system has been used to measure the variation in microhardness with applied load and orientation of WC crystals. The orientations of the individual crystals were measured using an electron backscatter diffraction (EBSD) technique. The WC crystals were ∼100 μm in size, embedded in a copper alloy matrix, to enable arrays of multiple microhardness indents to be implanted in each grain, thus generating good statistical validity for the results. It was found that the most significant effect on microhardness was the angle between the plane of measurement and either the basal or prism planes. A simple cosine rule, in line with resolved shear stresses, was used to correlate the data. The results are compared with previous studies using Knoop, Vickers and Berkovitch indenters, and some discussion is included of observed deformation around indentations using electron imaging associated with the EBSD technique.