The decomposition of Si3N4 in titanium and its effect on wear properties

Abstract

The use of silicon nitride (Si3N4) particles as potential reinforcement for titanium metal matrix composites (Ti-MMCs) was evaluated. Si3N4/Ti composite samples were fabricated by a conventional press and sinter route. The effects of sintering temperature and the concentration of Si3N4 in Ti matrix were investigated with respect to phase constituents, microstructure and tribology properties. Si3N4 weight fraction inside the Ti matrix was found to be the key parameter determining phase constituents and overall properties even at lower concentrations. Because of its instability in Ti at higher temperatures, in situ reactions between the reinforcing particles and matrix led to the formation of phases such as Ti5Si3 and possibly Ti3Si, in the composites containing higher fractions of Si3N4. The formation of homogeneous Ti5Si3 phase resulted in excellent wear properties at the expense of ductility. The wear resistance was directly proportional to the weight fraction of Si3N4. The highest hardness value 949HV1 was recorded for Ti-5 wt% Si3N4 composite when sintered at 1300 °C for 3 h. This work will benefit in understanding these composites as a prospective wear resistant material in industrial applications.