Variation of Mechanical Properties with Ni/Co Ratio in WC–(Co–Ni) Hardmetals

The effect of the Ni/Co ratio in WC–10(Co–Ni) and WC–15(Co–Ni) alloys on microstructure, density, hardness, and transverse rupture strength is investigated. The specimens have been prepared by mixing WC powders of 5·7 μm with Co and Ni powders. The compacts have been sintered in vacuum to full density. The density after sintering decreases slightly with increasing Ni content, and the effect is attributed to the increase of C content with Ni, which contains less oxygen than Co in powder form. The hardness decreases with Ni content and appears to depend mainly on the hardness of the matrix alloy phase. The transverse rupture strength does not show any variation with Ni content and appears to depend on the grain size, which also remains unchanged. The results show that Co in WC–Co hardmetal can be replaced by Ni without greatly affecting the transverse rupture strength if the microstructure remains constant. PM/0289