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 Si3N4 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 Si3N4. In this study, Cu-containing Si3N4 was prepared by in-situ method using copper citrate as the second phase additive. The highly dispersed second phase helped Si3N4 achieve significant improvements in fracture toughness and tribological properties. The phase composition, microstructure, hardness, fracture toughness, and tribological properties of Cu-containing Si3N4 were investigated. XRD results indicated that the reinforcement phase was in the form of Cu3Si. When the Cu3Si phase content was 3wt%, the fracture toughness of Cu-containing Si3N4 could be increased by 27.1% compared to the Si3N4. When the Cu3Si phase content reached 12wt%, 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 Cu3Si phase. The anti-wear mechanism could be concluded as the reduction of micro-cracks in the friction film with the participation of Cu3Si phase, thus reducing the loss in the friction process.