Tribological performance of functionalized ionic liquid and Cu microparticles as lubricating additives in sunflower seed oil

•Cu microparticles exhibited excellent tribological properties.•Synergic effect existed between [EAMIM]BF4 ionic liquid and Cu microparticles.•The mechanisms of [EAMIM]BF4 ionic liquid and Cu microparticles were studied.•A tribological model of Cu particles and [EAMIM]BF4 ionic liquid was established.

The functionalized 1-ethoxycarbonylmethyl-3-methylimidazolium tetrafluoroborate ([EAMIM]BF4) ionic liquid and the polyvinyl pyrrolidone protected Cu microparticles were synthesized and characterized. The tribological properties were investigated by a four-ball tribometer and the friction mechanisms are also discussed. The results demonstrate both the [EAMIM]BF4 ionic liquid and Cu microparticles possess the excellent tribological behaviors that can remarkably improve the friction-reduction and anti-wear properties of sunflower seed oil. Moreover, the tribochemical reaction film, which consists of copper, copper oxide, iron oxide, iron boride and boron trifluoride etc., was formed on the worn surface. The synergistic lubricating effect was produced and a tribological model of Cu microparticles and [EAMIM]BF4 ionic liquid in the sunflower seed oil was established to explain the lubricating mechanisms.