Tribological properties and worn surface analysis generated by ashless and phosphorus-free additive in water-based lubricant

Abstract

Two kinds of ashless and non-phosphorus water-based lubricant additives, dodecenyl succinic acid monoesters and sulphurized dodecenyl succinic acid monoesters, were synthesized from dodecenyl succinic anhydride. The anti-wear and friction-reducing properties of the synthesized additives were evaluated using a four-ball machine, and the worn surfaces were analysed by scanning electron microscopy and X-ray absorption near-edge structure (XANES) spectrocoscopy. The tribological results show that the two kinds of additives exhibit good anti-wear and friction reduction properties as well as or better than oleate, which is an important commercial lubricant additive. The XANES results indicate that the tribofilms mainly consist of adsorbed layers and tribochemical layers, and more sulphate and less sulphide in the films would result in lower friction coefficient. The XANES results also show that thriboheat has important influences on the tribofilms' formation. The mechanism of film formation is proposed.