Ultralow friction and low wear behavior of in-situ formed NiTiO3 from 60NiTi alloy at 350 °C

Abstract

Self-lubricating materials of NiO–TiO2 binary system have been rarely studied. In this paper, the friction experiments between 60NiTi discs and Si3N4 balls under dry friction conditions were carried out in ambient air from room temperature (RT) to 400 °C. The mechanical properties of each phase of 60NiTi after the friction experiments at different temperatures are measured by nanoindentation tests. The results show that the mechanical properties of the NiTi2 phase are best, and overall mechanical properties of 60NiTi get worse at 400 °C. The coefficient of friction (CoF) and wear rate basically drop from RT to 350 °C and rise at 400 °C. The behavior of ultralow friction and low wear is achieved at 350 °C with a CoF of 0.069 and a wear rate of 0.990 (mm3/mN) × 10−5. As temperature rises, the in-situ formed NiTiO3 ceramic plays a key role in improving tribological properties. The friction mechanisms at different temperatures are discussed systematically.