Comparative studies of WC-Co and WC-Co-Ni composites obtained by conventional powder metallurgy

A comparative study is given of cemented carbides of compositions WC-6Co, WC-10Co, WC-20Co, WC-6Co-6Ni and WC-12Ni-6Co. The purpose was to study the powder metallurgical production process of these compositions starting from a commercial WC-6Co powder, obtaining the desired compositions by mass balance with pure Co and pure Ni powders. During the process steps of mixing, milling, compacting and sintering the powders were described by their apparent density, green density, shrinkage and sintered density. Lower densities were observed in composites with higher binder content. The process was monitored by SEM and EDS analysis to evaluate the homogeneity of the powders, to detect contaminations by the process and to characterise the microstructure of the sintered materials. A finer microstructure was found when the binder contained Ni. Potentiodynamic polarisation tests in H2SO4 revealed pseudo-passive behaviour for all the tested hard metals.