Geometric and crystallographic characterization of WC surfaces and grain boundaries in WC-Co composites

Electron backscattered diffraction has been used to determine the orientation of WC crystals in a WC-Co composite and atomic force microscopy has been used to measure the shapes of planar sections of the same crystals. A stereological analysis has been used to determine that {10 (1) over bar0} prism facets and the {0001} basal planes are the WC surfaces that are most frequently in contact with Co. Further, the WC habit is an approximately equiaxed trigonal prism bound by three prism facets and two basal facets. An analysis of similar to15,600 grain boundaries shows that certain interfaces occur with a frequency that is much higher than would be expected in a random distribution and that the grain boundary habit planes also have {10 (1) over bar0} and {0001} orientations. Eleven percent of all the observed WC-WC interfaces are 90degrees twist boundaries about [10 (1) over bar0]. Two types of boundaries with a 30degrees rotation about [0001], a twist and an asymmetric tilt, comprise 3% of the population.