In-situ formation reinforcement phase for Si3N4 ceramics with high toughness and wear resistance

Soft metal as the second phase to enhance the mechanical and tribological properties of Si 3 N 4 ceramics was a focus of current research. Limited by the doping method and the low melting point of the metal, there were often phenomena such as nonuniform distribution and melting overflow of the second phase, which seriously deteriorated the properties of Si 3 N 4 . In this study, Cu-containing Si 3 N 4 was prepared by in-situ method using copper citrate as the second phase additive. The highly dispersed second phase helped Si 3 N 4 achieve significant improvements in fracture toughness and tribological properties. The phase composition, microstructure, hardness, fracture toughness, and tribological properties of Cu-containing Si 3 N 4 were investigated. XRD results indicated that the reinforcement phase was in the form of Cu 3 Si. When the Cu 3 Si phase content was 3 wt%, the fracture toughness of Cu-containing Si 3 N 4 could be increased by 27.1 % compared to the Si 3 N 4 . When the Cu 3 Si phase content reached 12 wt%, the wear rate at room temperature was reduced by 59 % compared to the substrate. The toughing mechanism could be summarized as the crack bridging and deflection of the Cu 3 Si phase. The anti-wear mechanism could be concluded as the reduction of micro-cracks in the friction film with the participation of Cu 3 Si phase, thus reducing the loss in the friction process.