Grain boundaries in WC-Co hardmetals with facetted and rounded WC grains

WC/WC grain boundaries in ultra-coarse WC-Co hardmetals with different shapes of WC grains were examined by STEM/EDX. Most WC/WC grain boundaries in the hardmetal with a medium-high carbon content containing facetted WC grains do not comprise nm-thick Co interlayers, although there are grain boundaries containing Co interlayers in its microstructure. The majority of WC/WC grain boundaries is the hardmetal with a medium-low carbon content containing rounded WC grains comprise nm-thick Co interlayers. The difference in the state of the WC-WC grain boundaries is presumably related to various wetting rates of tungsten carbide by liquid Co-based binders with various carbon contents.