Performance and mechanisms of silicate tribofilm in heavily loaded rolling/sliding non-conformal contacts

Lubricant performance is vital as heavy-duty gear manufacturers increase power density in their efforts towards increased efficiency. In this work, a recently developed ionic liquid is introduced as a multifunction additive for use in hydrocarbon base fluid. A ball-on-disc tribological test machine was used to evaluate friction and wear in heavily loaded mixed rolling/sliding conditions. The novel multifunctional additive is benchmarked against conventional axle-gear oil additives, and results shows excellent tribological performance in terms of friction and wear. Post-test surface analysis of the wear scars revealed a silicate based tribofilm derived from the novel ionic additive, contrary to conventional phosphorous and/or sulfur based. The silicate tribofilm is correlated to a significantly increased wear resistance and vastly improved running-in performance. [Display omitted] •A novel additive is evaluated in conditions relevant to heavy-duty gears.•Tribo-performance in heavily loaded mixed rolling/sliding conditions was excellent.•Improved friction and wear performance is attributed to a novel silicate tribofilm.