Microstructure and mechanical properties of cellular (Ti,M)(C,N)-based cermets fabricated by pre-granulation and subsequent vacuum sintering

Abstract

Cellular (Ti,M)(C,N)-based cermets were fabricated through pre-granulation followed by vacuum sintering. In this study, (Ti,Mo)(C,N) and (Ti,W,Ta)(C,N) solid solutions were utilized as hard phase components in agglomerates. The effects of the (Ti,M)(C,N) powders on the microstructure and mechanical properties of cellular cermets were studied. Cermet A, incorporating (Ti,Mo)(C,N) in the agglomerates, exhibited a cellular microstructure with double-layered agglomerates distributed in the matrix. By contrast, cermet B, which included (Ti,W,Ta)(C,N) in the agglomerates, exhibited a notable contrast between the agglomerates containing irregular elongated grains and the matrix. The mechanical properties of the cellular cermets were analyzed comprehensively in conjunction with the fractal dimension. Compared with cermet A, cermet B exhibited more transgranular fractures within the matrix, with dimples and tearing ridges visible in the agglomerates. Additionally, increased crack deflection, bridging, and bifurcation were observed near the interface, considerably impeding crack propagation. Overall, cermet A with significantly refined grains demonstrated higher hardness and TRS. The fracture morphology and crack propagation in cermet B were more complex and layered, resulting in the enhanced fracture toughness.