Comparing the Tribological Properties of Chloride-Based and Tetra Fluoroborate-Based Ionic Liquids

Methyl-imidazolium based ionic liquids have good tribological properties, because of their ability to form a chemically reacted film on the surface. This paper mainly compares the tribological properties of two ionic liquids, namely, the chloride-based imidazolium ionic liquid (IL1) and the tetrafluoroborate-based methyl-imidazolium ionic liquid (IL2). The two ionic liquids were synthesized in the lab and blended with mineral base oil at various proportions, i.e. 0.5 %, 1 % and 1.5 % by weight. The tribological properties of the oil samples were tested for 1hr on a reciprocating wear testing machine using a ball-on-flat configuration. The flat is made of hardened AISI 52100 steel, while the bearing ball made of the same material serves as the counter facing surface. The results show that IL2 exhibited a nearly 40% smaller friction coefficient than IL1 at 100 degrees C; the IL1 was found to corrode the steel specimens at 100 degrees C; the AFM images showed the formation of chemically reacted tribofilms on the surface of samples tested with IL2; SEM and EDS results proved the presence of chlorine, boron, and fluorine on the respective wear tracks.