Effect of (Ti, W, Mo, V)(C, N) powder size on microstructure and properties of (Ti, W, Mo, V)(C, N)-based cermets

Abstract

Three kinds of (Ti, 15W, 5Mo, 0.2V)(C, N) powders with different particle size were prepared from a mixture of oxides and carbon powders by carbothermal reduction-nitridation method. (Ti, W, Mo, V)(C, N)-based cermets were obtained by mixing Co, Ni, WC, MoC2 and (Ti, 15W, 5Mo, 0.2V)(C, N) powders, and then processed via a conventional P/M technique. The influence of (Ti, 15W, 5Mo, 0.2V)(C, N) particle size on the microstructure and mechanical properties of (Ti, 15W, 5Mo, 0.2V)(C, N)-5WC-10MoC2-7Co-8Ni cermets has been studied. When the particle size of (Ti, W, Mo, V)(C, N) is 0.2–0.5μm, (Ti, 15W, 5Mo, 0.2V)(C, N)-based cermets can be characterized by weak core/rim structure. With the particle size of (Ti, W, Mo, V)(C, N) increasing to 1–1.5μm, the microstructure of (Ti, 15W, 5Mo, 0.2V)(C, N)-based cermets develops into composite structure that consists of typical core/rim and no core/rim. Accordingly, typical core/rim structure is obtained in the case of the particle size of 3–5μm. With the coarsening of raw (Ti, 15W, 5Mo, 0.2V)(C, N) powders, the fracture toughness of (Ti, 15W, 5Mo, 0.2V)(C, N) cermets is greatly improved, but the hardness continues to decline. (Ti, 15W, 5Mo, 0.2V)(C, N) cermets with composite structure have higher bend strength of 2165MPa.