Investigating the Antiwear Characteristics of Castor Oil Based IonanoLubricant Using Four Ball Tester

Environmental issues due to excessive use of mineral and synthetic oil have forced us to develop environmentally acceptable lubricants. Non-edible vegetable oils are the most suitable alternative to the base oil. The present study aims to investigate the synergistic effect of copper oxide (CuO) nanoparticles and halogen-free ionic liquid (IL) trihexyltetradecylphosphonium bis (2,4,4 trimethylpentyl) phosphate [P66614] [BTMPP] in castor oil as hybrid additives. Antiwear properties of ionanolubricants have been compared with castor oil containing ZDDP (common antiwear additive). The shape morphology and particle size of CuO nanoparticles (<80nm) were investigated using FESEM. Three samples were formulated with castor oil containing 0.02 volume fraction CuO, 0.1 vol/vol% [P66614] [BTMPP] IL and 2% ZDDP, respectively. Three other samples were formulated by varying the concentration of CuO in 0.02, 0.04 and 0.06 volume fractions and IL in 0.1, 0.2 and 0.3 vol/vol%, respectively. Antiwear characteristics of formulated ionanolubricants have been investigated using a Four ball tester under ASTM D 4172 B. The worn-out surfaces of steel balls were investigated using optical microscopy. An average wear scar diameter (AWSD) of 0.589 mm was found at an optimum concentration of 0.02 volume fraction CuO and 0.1 vol/vol% IL. AWSD has increased with an increase in concentration of both additives. The steel balls show the lowest AWSD at optimum concentration of additives. The lowest AWSD of 0.514 mm was found for castor oil containing 2% ZDDP. This study shows that formulated castor oil based ionanolubricants are environmentally acceptable and provide better antiwear properties.