Some aspects of the structure of cobalt and nickel binder phases in hardmetals

This paper reports the assessment of the structure of Co and Ni binder phases in hardmetals, principally by electron backscatter diffraction. The binder phase is shown to form, in most cases, very large regions of a single-crystallographic orientation up to 50 times greater than the mean size of the WC grains between which the binder phase penetrates. The hexagonal close-packed form of Co appears to form much smaller grains but the orientations measured show that this results from the growth of a few variants on cooling from large face-centred cubic grains. Ni binder materials can form both large and small grains, a difference which can be detected by measurement of resistivity and magnetic moment.