EFFECT OF TIN ADDITION ON SINTERING BEHAVIOR AND MECHANICAL-PROPERTIES OF WC-10CO HARD METALS CONTAINING MO2C AND NI

The aim of the present work was to substitute a portion of WC in WC-10 wt% Co hard metal by TiN by modification of the binder phase, and to produce an equivalent grade of hard metal. Sintering studies were carried out in both H-2 and H-2-N2 (50:50) mixture. Introduction of TiN into WC-10Co hard metal resulted in a high sintered porosity, and as a consequence the mechanical properties deteriorated. Partial substitution of cobalt in WC-8.7TiN-12Co by nickel further increased the sintered porosity and led to a non-uniform microstructure. Incorporation of Mo2C along with cobalt-nickel binder promoted a fine-grained structure, which resulted in better sintered properties than those of WC-8.7TiN-6Co-6Ni hard metal. However, hot isostatic pressing (HIP) treatment of the liquid-phase sintered alloys was effective in eliminating the large pores and thus greatly enhanced the mechanical properties. HIPed hard metal of WC-8.7TiN-12Co composition showed properties almost equivalent to those of WC-10Co hard metal.