On The Mechanisms Of Ultra-low Wear Polytetrafluoroethylene-Based Lubrication Interface Formation And Filler Functionalities

Polytetrafluoroethylene（PTFE）has excellent lubricating properties and thermal/chemical stability,thus widely used in solid-lubricated mechanical systems serving in harsh working environments such as aerospace,low-temperature,and dry conditions.Based on traditional design methods,the use of high hardness,micron-sized fillers can only partially improve the service life of PTFE solid lubricants.The ultra-low wear interface design using the functionalities of fillers can increase the service life of PTFE solid lubricants by 3 to 4 orders of magnitude.Understanding the formation mechanism of ultra-low wear PTFE solid lubricating interface can be applied to design solid lubricating systems with longer service life.In this study,the formation of ultra-low wear PTFE solid lubricating interface and the functionalities of fillers were investigated with microscopic characterization,environmental tests and theoretical calculations.First,based on the previous researches on the interface load support mechanism and the transfer film protection mechanism,a synergistic mechanism for realizing the ultra-low wear interface through the joint action of the two mechanisms is proposed.The study found that the Ga N fiber/PTFE solid lubricating material that satisfies the synergistic mechanism has a wear rate of 1×10^-7 mm³/Nm,showing obvious ultra-low wear characteristics.The solid lubricating materials of the control groups did not meet the interface load supporting mechanism or transfer film protection mechanisms,which failed to form the ultra-low wear interface.The study proves that the use of synergistic mechanism is an effective way to realize ultra-low wear PTFE solid lubrication system.Subsequently,the relationship between the surface chemical functionalities of fillers and the formation of ultra-low wear PTFE solid lubricating interfaces was investigated.Density functional theory calculations were used to investigate how the chemical functionalities of filler surfaces affect the tribochemical reaction process of PTFE molecules.The results show that the electrophilic sites on the metal oxide/nitride fillers’surface can promote the formation of carboxylic acid functional groups in PTFE,which improves the interfacial load support and transfer film protection of the composites,resulting in the formation of ultra-low wear interfaces.Environmental tests further verified the theoretical calculation results.Studies have demonstrated that the surface chemical activity of metal oxide/nitride fillers can promote the formation of ultra-low wear PTFE solid lubricating interfaces.Third,the effect of the microstructural functionality of the fillers on the formation of the ultra-low wear PTFE solid-lubricating interface was further investigated.Taking the microstructure and functionality of graphene fillers as the research object,using transmission electron microscopy,photoelectron spectroscopy,and low-temperature nitrogen adsorption and desorption experiments,it was studied how the microstructure functionality affects the filler/matrix bonding strength and how it acts on ultra-low wear solids The formation of the lubricating interface,the study found that the filler/matrix interaction surface area can be used as a quantitative index of the microstructure and functionality of the filler,and the application of this index to tribological design can control the wear resistance of PTFE solid lubricants.Finally,based on the synergistic mechanism and the functional effect of fillers,an ultra-low wear interface design method using the interface polar interaction is proposed,and an ultra-low wear PAI/PTFE solid lubricant for harsh dry environments is designed.Molecular dynamics simulation results predict that the polar functional groups of PAI fillers can promote the formation of ultra-low wear interfaces of the solid lubricating material in a harsh dry atmosphere.The ultra-low wear rate of mm3/Nm,infrared spectroscopy revealed that the iron-based counterpart of PAI/PTFE formed a cohesive polar transfer film in a dry environment,which proved that the ultra-low wear formation mechanism and filler functional role can be applied solid lubrication interface design under special conditions.The research results establish a scientific connection between surface chemical reaction,micro-mechanical behavior and macro-wear phenomenon,expand the theory and method of ultra-low wear solid lubrication system design,reflect the current development trend of multi-discipline in engineering scientific research,and have important theoretical and practical significance.