Tribological performance study of oil-soluble ILs as lubricant additives by the four-ball method

Four oil‐soluble ionic liquids (ILs) with different structures were synthesised: N88816‐Doss (N/S), P88816‐Doss (P/S), N88816 phosphate (N/P) and P88816 phosphate (P/P). The effects of the four ILs synthesised with conventional lubricating additives isobutylene sulfide (T321), zinc dialkyl dithiophosphate (ZDDP) and tricresyl phosphate (T306) as PAO10 additives on the physicochemical properties of the prepared oil samples were systematically investigated at the same dosing rates. The antifriction and antiwear properties and extreme pressure performance of oil samples prepared by four ILs and three conventional additives were investigated by a four‐ball friction and a wear testing machine. The results showed that P/S improved the thermal stability of PAO10. The addition of N/S significantly improved the tribological performance of PAO10 at room temperature and under heavy loading. The coefficient of friction was reduced by 90%, the wear spot diameter is decreased by 28%, the last non‐seizure load PB is doubled, and the resistance to sintering did not improve.