Effect of short carbon fibre concentration on microstructure and mechanical properties of TiCN-based cermets

Short carbon fibre (C-f) reinforced TiCN-based cermets (C-f/TiCN composites) were produced by powder metallurgy method with pressureless sintering technology. The phase evolution, microstructure and fracture morphology of C-f/TiCN composites were investigated. The results showed that TiC, TiN, WC, Cr3C2 and Mo phases disappeared gradually and diffused into core and rim phases by dissolution-reprecipitation process, finally formed new hard TiCN core phases and complex compound (Cr, W, Mo, Ti)(CN) rim phases, with the sintering temperature increasing. The added C-f did not change the core-rim' microstructure but improved the mechanical properties of TiCN-based cermets. The C-f/TiCN composite containing 3wt-% C-f achieved the best comprehensive mechanical properties, with fracture toughness and bending strength increasing by about 14.4% and 30.8%, respectively, when compared with the composite without C-f. Toughening and strengthening mechanisms of C-f/TiCN composite were concluded as crack deflection and branch, as well as the pull-out, fracture and bridging of carbon fibres.