Effect of two halogen-free ionic liquids with different anions on the tribological properties of TC4

Two halogen-free ionic liquids (ILs), P888p-DABD and P888p-DOSS, are designed and synthesized to improve the tribological performances of TC4. The difference between the two ILs is the anion: one is composed of sulfonate base anions, and the other is composed of ammonium dibutyl dithiophosphate anions. The thermal stability, tribological performances and anti-corrosion performance of the two ILs were evaluated. The results show that P888p-DOSS has better tribological performance than P888p-DABD and can be used as a lubricant for Si3N4/TC4 friction pair. Based on the three-dimensional (3D) profile, SEM, EDS, and the XPS analysis of the worn surfaces of TC4 discs, the P888p-DOSS has excellent anti-friction and anti-wear properties mainly because of the complex tribochemical reaction between the ILs and TC4 matrix, which forms a protective film with anti-friction and anti-wear performance. This provides theoretical guidance for light alloy lubrication.