Tribological properties of graphene/β-Si3N4 whisker reinforced Si3N4 ceramic composites

Abstract

Exploring ceramic-based self-lubricating materials with low coefficient of friction (COF) has become one of the hot directions to advance the service performance and life of high-end equipment. In this work, the tribological properties of multilayer graphene (MLG)/β-Si3N4 whisker (β-Si3N4w)/Si3N4 ceramics were investigated. The effects of load and linear speed on the dry sliding COF were discussed. The friction-reducing and self-lubricating mechanisms of MLG and β-Si3N4w were deeply analyzed according to the wear morphology and mechanical properties of Si3N4-based ceramics. The friction frequency was proposed to analyze the wear mechanism. Results indicated that MLG and β-Si3N4w led to a breakthrough reduction in COF. At the load of 5–20 N, the COF reached an ultra-low level of 0.04–0.07, which was a further 89.86% lower than the reported studies. The comprehensive enhancement of mechanical properties and the existence of MLG lubricating film were the mainly responsible for the ultra-low COF. The COF of MLG/β-Si3N4w/Si3N4 ceramics raised to 0.24–0.31 at 50–200 mm/s, but it was still 33.88–47.64% lower than that of graphene/Si3N4 ceramics. The increase in COF was attributed to the high wear induced by the raised friction frequency. The furrow wear and adhesive wear were the main wear forms of MLG/β-Si3N4w/Si3N4 ceramics.