Tribological behavior of lubricating oil additives in lubricated aluminum-on-steel contact

Effects of some commercial lubricating oil additives on the tribological properties of aluminum alloy in sliding contact with bearing steel were investigated under boundary lubrication using a reciprocating wear tester. It was shown that base stock containing 1 wt.% additive is not effective at reducing the friction and wear of aluminum alloy. Furthermore, additives, except sulfurized olefin, at 5 wt.% in the base stock have pro-wear properties. The beneficial effects of base stock containing 5 wt.% sulfurized olefin were attributed to the formation of Al₂O₃ film at the contact area, which was identified by X-ray photoelectron spectroscopy (XPS) and electron probe microanalysis (EPMA).