Additive–Additive Interaction: Understanding Synergistic and Antagonistic Effects of Additives in Neat Cutting Oil Formulation

This research work presented here is a comprehensive study on additive–additive interaction with respect to their anti-wear, anti-friction, and extreme pressure characteristics when one or more additives are used in combination in a lubricant formulation. Two tribological equipment, viz., four-ball tester and SRV tester were used to assess the performance of different additive chemistries, which are typically used in formulating neat cutting oils. The following additive chemistries were utilized for this study: natural ester, sulfurized ester, chlorinated paraffin, phosphate ester, and sulfurized olefin. Three different dosages of these chemistries were initially mixed with a mineral-based oil and subsequently evaluated for their tribological performance. The most effective additive dosage (in percentage) from individual additive chemistry was selected for further investigation of the combination of two additives. Tribological testing of formulations involved the measurement of wear scar diameter, coefficient of friction at different test conditions, and weld load. Several combinations of additives in the experiments yielded remarkably and enhanced tribological performance indicating synergism, while antagonistic effects of some combinations were observed.