LAUSR

In recent years, ionic liquids have shown great potential as an additive in lubricants. However, most of the explored ionic liquids for machining applications contain halogen-based anions, which are sensitive to moisture and have a tendency to produce harmful halogen acids (HX) after reacting with water/moisture. These acids are harmful to the environment and can corrode the working surfaces. This study investigates the effectiveness of halogen-free ionic liquids as potential additives to vegetable oil (canola oil). Two halogen-based ionic liquids (1-methyl 3-butylimidazolium tetrafluoroborate [BMIM BF4] and 1-methyl 3-butylimidazolium hexafluorophosphate [BMIM PF6]) and one halogen-free ionic liquids (trihexyl tetradecyl phosphonium bis (24,4-trimethylpentyl) phosphinate P6,6,6,14 [i(C8)2PO2]) were blended individually with canola oil. The percentage ratio of ionic liquid to canola oil is 1:99. Dynamic viscosity and contact angles of different lubricants were measured. Sliding tests were conducted in various conditions; dry, canola oil, and three different blends of ionic liquid with canola oil. Further, to connect tool-chip tribology with machining, turning experiments were carried out under similar lubricating conditions. Results show that the sliding friction, pin surface temperature, and wear were reduced by 48.1%, 44%, and 69.6%, respectively, due to better lubricating ability and spreading tendency of halogen-free ionic liquid blended with canola oil. The microscopic analyses of pin surfaces and the morphology of counter disc surfaces further supported better lubrication between the sliding pair. For P6,6,6,14 [i(C8)2PO2] ionic liquid blended with canola oil, the average cutting temperature and machined workpiece surface roughness reduces by 43.6% and 62.4% compared to dry machining.