Sintering injection-moulded WC-7 wt % Ni in a hydrogen atmosphere at temperatures higher than 900 degrees C resulted in an inhomogeneous microstructure, as Ni2W4C (eta phase) preferentially developed near the surface of specimens. Subsequent to sintering at temperatures higher than the liquid-phase formation temperature, the surface of specimens was virtually composed of eta phase. This arose from the excessive decarburization occurring near the surface of specimens, and the exudation of the Ni-based metal binder towards the surface of specimens. Primarily caused by the dissolution of W into the Ni binder phase, the saturation magnetization of WC-7 wt % Ni decreased at temperatures lower than 1000 degrees C.