Tribological behavior of three silicon nitride ceramics in dry sliding contact against Inconel 718 over a wide range of velocities

Silicon nitride based ceramic tools have been successfully applied in high speed machining of nickel-based alloys. In this study, three silicon nitride material systems with different intergranular glassy phase contents were used to study the tribological behavior of silicon nitride in dry sliding against Inconel 718 in order to evaluate their potential suitability as cutting tool materials. The tribological properties at sliding velocities ranging from 1 m/s to 20 m/s were investigated. The mechanical and microstructural properties of the ceramics were considered, and the wear mechanisms were analyzed. The results showed that the wear of the ceramics has a positive correlation with hardness for sliding velocities below 5 m/s. With increasing sliding velocity, a tribochemical layer consisting of an oxide layer and a diffusion layer forms at the interface, resulting in increasingly higher wear of the ceramic. The formation of a tribochemical layer showed a correlation with the amount of the intergranular glassy phase in the material; the higher its amount the more prone the silicon nitride ceramic was found to form a tribochemical layer.