WC/Co-composite powders via hydrothermal reduction of Co3O4-suspensions

Due to the strong influence of the cobalt distribution in the green powder compact on the quality of the sintered hardmetal alloy, intensive powder milling and a balanced ratio of WC to Co powder particle size are usually required to achieve uniform carbide-microstructures.In the past many attempts have been made to reduce or avoid powder milling and to improve the quality of the powder mixture by chemical means. The research described below focused on a new route to carbide coating comprising oxide-pressure-precipitation of submicron to nano-sized Co3O4-suspensions from cobalt solutions, mixing with WC-suspensions and subsequent hydrothermal reduction of those suspensions in hydrogen atmosphere. The effects of WC addition and catalyst addition on the progress of cobalt oxide reduction are discussed. The resulting cobalt and composite powders were characterised via powder diffraction, SEM and TEM imaging. Sintering tests confirmed the uniform Co distribution.