Tribological properties of 2 novel Mo/B-based lubricant additives in polyalphaolefin

Two kinds of Mo/B oleic diethanolamide derivatives (coded as YXM and YXB) were synthesised, and their tribological properties were evaluated using a 4-ball machine. Results indicate that the 2 novel additives show excellent antiwear and extreme pressure properties. When 2.5 wt% YXM was added into the base oil, the wear scar diameter was reduced by 42.2%, and the PB value was increased by 170.4%; when 2.5 wt% YXB was added into the base oil, the wear scar diameter was reduced by 23.1%, and the PB value was increased by 167.1%. The worn surfaces of the lubricated GCr15 steel were analysed by using scanning electron microscopy and X-ray photoelectron spectroscopy. It is indicated that the variation of tribofilm species produced by a chemical reaction between the additives and the steel surface plays an important role in inhibiting wear and friction. A model was used to analyse the action mechanism. According to the analysis, the tribofilm is composed of an adsorption layer and a reaction layer, and it could effectively protect the steel surfaces from direct contact.