Hardness and deformation of tungsten carbide--cobalt alloys

An attempt was made to relate mechanical properties, such as hardness and Young's Modulus, of cemented tungsten carbide to the microstructure of the alloys by combining the concepts of dispersion hardening and carbide skeleton deformation. The particle size, binder mean free path and contiguity were obtained by linear analysis of electron photomicrographs. It was shown that the carbide particles form a continuous carbide skeleton through direct carbide--carbide contacts. The degree of continuity was discussed in terms of contiguity. The volume fraction of this continuous carbide skeleton was calculated to be equal to the volume fraction of the carbide phase multiplied by the contiguity of that phase. The concept of plastic limit analysis was used to evaluate the effect of the carbide skeleton on the hardness. The hardness of the carbide and matrix phases is a function of particle size and mean free path. The present structure model predicts a highly concentrated stress at the junctions of the carbide skeleton. Indeed, slip at carbide--carbide contact points and failure of these contacts on extensive deformation was frequently observed in an electron microscopic study of the deformation of these alloys