Tribological properties of polytetrafluoroethylene as additive in titanium complex grease

Purpose - The purpose of this paper is to study, analyze and present the lubricating mechanism and tribological properties of two types of oil-based titanium complex grease containing Polytetrafluoroethylene (PTFE).Design methodology approach - Two types of oil-based sebacic acid stearic acid titanium complex greases containing PTFE additive were synthesized using 3 L reaction vessel, and the base oils including neopentyl polyol ester and mixed oil of 650SN and neopentyl polyol (1:1.8). Friction-reduction, antiwear, and load-carrying properties of greases were evaluated using a four-ball tester, and their dropping point and penetration were characterized using relevant ASTM standards. Morphologies of wear scar and chemical states of typical elements on worn surfaces were characterized by means of scanning electron microscope and X-ray photoelectron spectroscopy, respectively.Findings - Tribological results show that titanium complex grease containing PTFE had better friction-reduction and antiwear properties than base grease. However, PTFE could not improve the load-carrying capacity of base grease. Moreover, a synergistic effect between deposited film and adsorptive film contributes to good tribological properties of titanium complex grease.Practical implications - Such a very useful lubricating material could be used in industrial applications including steel plants, power plants, packaging, and fertilizer industries.Originality value - The lubricating mechanism of titanium complex grease containing PTFE was proposed by tribochemical analysis of worn surfaces. The mechanism should become the direction of the theoretical and applied research of grease in the future.