High Temperature Wear Behaviour of Silicon Nitride

Self-mated hot-pressed silicon nitride specimens have been tested with a flat-on-flat geometry at room and high temperature in order to evaluate the magnitude of wear, coefficient of friction and mechanisms of wear. As a general rule, wear and friction coefficient do not seem to be related each other: wear increases with the temperature, even if in a non linear way, up to 900°C, while the friction coefficient first raises and then slightly decreases. At 1200°C, the wear was greatly reduced by the presence of a viscous semi-liquid layer between the sliding surfaces with a correspondent increasing in the friction coefficient.