Improved Friction and Wear Performance Utilized with Aminoguanidine-Based Ionic Liquid Over Wide Temperature Range for Reciprocating Frictional Contact Surface

Aminoguanidine-based ionic liquid which can reduce the friction coefficient and wear depth has been developed as lubricant additives for the piston ring and cylinder liner within 80–240 °C. The friction coefficient and wear depth reduction become more significant as the temperature increases. At 240 °C, the coefficient of friction decreases by 23.1% compared to fully formulated mineral based engine oil (FFO). The wear depth of the piston ring and cylinder liner decreases by 9.1% and 16.0%, respectively. Addition of aminoguanidine-based ionic liquid (AO-IL) promotes the tribo-chemical reaction of zinc dialkylphosphorodithiloate (ZDDP), distributing S, P and Zn on the cylinder liner honing platform rather than in the honing groove. The plastic deformation causes a significant reduction of flakes on the edges of the cylinder liner honing platforms and less furrow damage along the sliding direction. The worn surface of the diamond-like carbon (DLC) piston ring shows a denser distribution of white bright spots and a higher sp²C=C/sp³C–C ratio.