Tribological Properties of Lubricating Additives of Phosphorus-based Halogen-free Oil-soluble Ionic Liquid

A new type of halogen-free ionic liquid was synthesized by using diisooctyl phosphate (EDHPA) as anion and diquaternary phosphate as cation. It was compared with commercial T306 as lubricating additive of PAO 10. The tribological properties were investigated by SRV - V friction and wear testing machine, the wear morphology was characterized by scanning electron microscope, the wear volume was measured by non-contact three-dimensional profilometer, the changes of friction film during the friction process were analyzed by ECR, and the chemical elements and changes of wear spot surface were analyzed by XPS. Results show that the new synthesized halogen-free ionic liquid has excellent tribological properties as an additive of PAO 10, and greatly improves the extreme pressure carrying capacity of PAO 10. The friction chemical reaction occurs in the friction process of the new ionic liquid, in which the long alkyl chain and polar element P form a dense and thick boundary lubrication film during friction, which improves the friction reducing, anti-wear and extreme pressure bearing properties of PAO 10 system.