Tribological Performance and Lubrication Mechanism of Alkylimidazolium Dialkyl Phosphates Ionic Liquids as Lubricants for Si3N4-Ti3SiC2 Contacts

The tribological performance of Si3N4-Ti3SiC2 contacts lubricated by alkylimidazolium dialkyl phosphates ionic liquids (ILs) was investigated using an Optimol SRV-IV oscillating reciprocating friction and wear tester at room temperature (25°C) and 100°C. Glycerol and tributyl phosphate (TBP) were also selected as lubricants for Si3N4-Ti3SiC2 contacts to study the tribological properties under the same experimental conditions for comparison. Results show that the alkylimidazolium dialkyl phosphates ILs were effective in reducing the friction and wear for Si3N4-Ti3SiC2contacts, and their performance is superior to that of glycerol and TBP. The SEM/EDS and XPS results reveal that the excellent tribological endurance of alkylimidazolium dialkyl phosphates ILs is mainly attributed to the high load-carrying capacity of the ILs and the formation of surface protective films consisting of TiO2, SiOx, titanium phosphate, amines, and nitrogen oxides by the tribochemical reactions