Tribological performance of phosphate ionic liquids as lubricants for steel-on-aluminum contact

Abstract

Anti-corrosion phosphate ionic liquids were synthesized and evaluated as lubricants for the contact of steel/aluminum by using an Optimol SRV oscillating friction and wear tester under ambient conditions. Phosphate ionic liquids yield commendable tribological performance and are superior to the conventional ionic liquid lubricant 1-methy-3-hexylimidazolium hexafluorophosphate in terms of friction-reducing performance and anti-wear capacity. Contrastive experiments demonstrate that the simple mixing of two compounds (butylamine and dibutylphosphate) does not yield a mixture lubricant with better tribological properties as compared to the ionic liquid synthesized using these two compounds. The worn surfaces of aluminum discs were analyzed by using JSM-5600LV scanning electron microscope and PHI-5702 multifunctional X-ray photoelectron spectrometer. The friction reducing and anti-wear mechanisms originate from the layered structures of ionic liquids under boundary lubrication conditions and from the tribochemical interactions of ionic liquids with the fresh surface of the substrates.