Influence of molybdenum addition on the microstructure and mechanical properties of TiC-based cermets with nano-TiN modification

Effect of Mo addition on the microstructure and mechanical properties of TiC-TiN(nm) WC-Co-Ni-C system cermets was studied in the work. Specimens were fabricated by conventional powder metallurgy techniques. The microstructure was investigated using transmission electron microscope (TEM) and the scanning electron microscope (SEM). Chemical compositions of different phases such as ceramic phase with core/rim structure [the core being TiC and rim being (Ti,W,Mo)(C,N)] and metallic phase were analyzed quantitatively by EDX. Mechanical properties such as flexural strength, fracture toughness and hardness were also measured. Results show that flexural strength and fracture toughness have a trend to decline with increasing Mo addition, but the change of hardness is not apparent with the increase of Mo addition. Results also reveal that finer microstructure and thicker rim phase will be obtained with the increase of Mo addition. The optimal addition of Mo can be estimated to be 4 wt.% with respect to TiC-10TiN(nm)-15WC-5Co-Mo-5Ni-1C system cermets. Fracture micrographs show that main failure mode of the cermets is a mixed one, i.e., trans-granular and inter-granular fractures both exist. (C) 2003 Elsevier Ltd and Techna S.r.l. All rights reserved.