The contiguity of carbide crystals of different shapes in cemented carbides

Equilibrium and geometry models for the contiguity of carbide crystals in cemented carbides are discussed. The equilibrium approach is applicable to rounded carbide crystals with a sufficient amount of the binder phase. Increase of the angularity of carbide crystals and/or decrease of the binder content lead to the geometrical constituent of the contiguity to be taken into account. In both cases, the energy advantage of the carbide-carbide contact over replaced carbide-binder interfaces determines the existence of the contact. An effect of the shape equiaxiality on the contiguity of WC crystals is observed in WC-Ni cemented carbides with small additions of TiC and explained by a model combining geometry and energy advantage of the contacts. The basal-to-basal, prismatic-to-prismatic, and prismatic-to-basal WC/WC contacts and their contribution to the decrease of the total contiguity are considered and evaluated separately in regard to the decrease of the shape equiaxiality of WC crystals.