High temperature tribological properties of a nickel-alloy-based solid-lubricating composite: Effect of surface tribo-chemistry, counterpart and mechanical properties

This paper is aimed to characterize the new NiCrAlMo-12.5 wt. % Ag- X wt. % CaF₂/BaF₂ (X = 5 or 10) solid-lubricating composites, which have high strength and self-lubricity simultaneously from room temperature to 800 °C and thus would be a potential candidate for aerospace bearing applications. Additionally, clarification of the influence of fluoride content on the tribological responses of this material is another object. Sliding friction and wear performances of these composites as bearing materials are evaluated using a pin-on-rotating-flat disc configuration against an Inconel718 alloy pin. Also, the surface tribo-chemical reactions and mechanical properties of the composites are investigated and related to their tribological behaviors. Reducing the fluoride eutectic content leads to significant improvement on the wear resistance of the composites above 600 °C, which is strongly dependent on the surface tribo-chemical reactions and the interaction with the counterpart, not on the mechanical properties. The wear rate of the Inconel718 counterpart over the entire testing temperature range is as low as 10^-7 mm³/(Nm).