Mechanical properties of (Ti_xW_1−x)C–Co cermet prepared by carbothermal reduction of high energy ball milled TiO₂–WO₃–C

A series of solid–solution carbides, (Ti_xW_1−x)C (x=0.9, 0.8, 0.7, 0.6), was prepared by the high-energy milling of TiO₂–WO₃–C mixtures via subsequent carbothermal reduction. With high-energy milling, only the size reduction of the constituent powders was apparent without any chemical reaction. The milled mixture powder was transformed to a single–phase (Ti_xW_1−x)C solid solution by heat treatment in a vacuum at 1200 °C. (Ti_xW_1−x)C–Co cermets were consolidated by isothermal sintering at 1300, 1400, and 1500 °C. The powders were fully densified by liquid-phase sintering at 1500 °C because the Co melted at 1430 °C. The mechanical properties of the (Ti_xW_1−x)C–Co cermet (H_v: ~24 GPa) were significantly better than those of the conventional WC–Co (H_v: ~13 GPa) or TiC–Co cermets (H_v: ~16 GPa). The use of a solid–solution carbide instead of conventional WC almost doubled its hardness values without a loss of toughness. It is indicated that the improved hardness of the (Ti_xW_1−x)C–Co cermet originates from the high hardness of (Ti_xW_1−x)C, and the solid–solution carbide would be a valuable substitute for conventional carbide cermets.