Tribological properties and lubrication mechanism of protic ionic liquid-modified nanosilica as high-temperature antiwear additive for pentaerythritol ester

Protic ionic liquid-modified nanosilica (SiO2-PIL) hybrid with excellent dispersion stability and thermal stability was prepared. The SiO2-PIL hybrid was used as a high temperature antiwear additive for pentaerythritol ester (PE) base oil, which exhibited better antiwear ability and load-carrying capacity at high temperature compared with triphenyl phosphate (TCP). This is attributed to the synergistic friction-reducing and antiwear effects of nanosilica and ionic liquid during sliding at elevated temperatures. Findings indicate that a protective tribofilm with sandwich structure composed of phosphate and amorphous carbon as the outer layer and silica nanoparticles as the interlayer was formed on the worn surface. Finally, combined with the adsorption behavior and the results of worn surface analysis, the high-temperature lubrication mechanism of SiO2-PIL was proposed.