Effect of lubricant additives on the tribological behavior of aluminum alloy against steel

Abstract

Abstract This study aims to understand the impact of various lubricant additives on the friction- and wear behavior of aluminum alloys against steel. Employing the aluminum alloy Al 6061 and the steel AISI E 52100 as representatives, we studied the effects of the main additives typically found in fully formulated lubricants individually by formulating model lubricants consisting of base oil and just one additive at a time. The additives we studied include sulfurized olefin, complex alkyl phosphate amine, alkyl phosphite, overbased calcium sulphonate, zinc dithiophosphate (ZDP), and calcium sulfonate detergents. For each model lubricant, as well as for the base oil and the fully formulated oil, we performed ball-on-disc experiments with aluminum alloy balls on steel discs. We obtained the friction coefficient, determined the wear volume of the aluminum alloy, and analyzed the composition of the wear surface. We found that all additives except calcium sulfonate detergents promote the formation of aluminum oxide. Among all individually tested additives, zinc dithiophosphate provides the best wear resistance, while sulfurized olefin provides the lowest friction. The lowest friction combined with the second lowest wear rate was actually observed for a fully formulated oil (containing an optimized mixture of several additives).