Binder phase structure in fine and coarse WC–Co hard metals with Cr and V carbide additions

Abstract

The effects of the grain refining additions V, Cr and the level of dissolved W on the structure of the Co binder phase and the hcp/fcc were investigated in this work alongside WC grain size. V was found to be a more effective grain size suppressor in materials with a coarser starting carbide grain size while Cr was more effective for finer grain material when overall WC grain size distribution was taken into account. Grain refiners and W levels had a significant effect on WC grain morphology with V additions in high W samples having a rounded appearance. Cr additions at both high and low W concentrations had a more prismatic appearance.The large scale structure of the fcc Co phase as imaged by EBSD was affected by WC grain size and carbon balance with high W leading to larger regions of similar orientation than those with higher carbon balance. V additions increased the size of fcc areas of similar orientation while Cr additions reduced them. Both the effect of additions and increased W suppressed hcp formation with hcp suppression more marked in coarser WC materials than finer WC materials. It is intended that more information on the binder phase will aid future modelling and exploration of WC–Co hard materials.