On Tribological Performance & Interface Transfer Behaviors Of Micro/Nano Multi-Scale Reinforced PFA Matrix Composites Worked With A Metal Pair

Perfluoroalkoxy（PFA）has temperature resistance,chemical stability and self-lubricating properties close to PTFE.As a friction material,it also has the necessary melt fluidity for molding and processing,which can overcome the difficult molding and poor processing performance of PTFE shortcomings.However,as a friction pair material,especially when paired with metals,there are problems such as low hardness,low strength,and insufficient wear resistance.The composite strengthening,especially the micro-nano multi-scale composite strengthening,is expected to solve these problems.To this end,this study used mechanical blending and hot pressing to prepare different combinations of micro/nano multi-scale composite reinforced PFA-based composites.Through experiments of the mechanical/tribological performance of the composites,the influence of different micro-scale enhancement phases and the types and contents of nano-addition phases on the performance of PFA was clarified.And combined with the characterization results of the local surface morphology and element di stribution in the wear area of the matching pair interface,the interfacial transfer behavior and the main possible mechanism of tribochemical reaction,was discussed.The research results can be summarized as follows:1)Micro-phase composite can significantly improve the carrying capacity of PFA,hinder the large-scale breakage of PFA molecular chains,and effectively reduce material wear.Compared with the uncomposited state,the tribological properties of the four discontinuous micro-phase-reinforced PFA-based composites are significantly improved.Among them,the wear rate of Gf/PFA is reduced by 3 orders of magnitude,while the friction coefficient of Ap/PFA is reduced by 34.69%,at the same time,the wear rate is also decreased by 2 orders of magnitude.The transfer films formed on the metal pair side after friction is more uniform and effectively reduces the direct contact between the composites and metal pair,which is the main reason for its good anti-friction and wear-resistant effect.2)When the nano-phase addition is less than 2wt.%,it has basically no effect on the hardness and compressive strength of micro-nano composite PFA-based composites.Its main function is to influence the friction and wear behavior and tribological properties of the composites through the synergistic effect of the addition of micro-nano different scales.Under this mechanism,the role of nano-phase content is not obvious,mainly because its type plays a leading role.When there is an unfavorable synergy effect between the micro-nano two-scale addition phases,the performance of the micro-nano reinforced composites becomes worse:1Al₂O_3n/10Gf/PFA has a greater wear rate than 10Gf/PFA,and the friction coefficient has not decreased.This is mainly due to the fact that Al₂O_3n removes the oxide layer and continuously scratches the interface exposed micro-phase Gf after the substrate PFA wear,which causes the accumulation of Gf debris in the wear debris to aggravate the abrasive wear.When Al₂O_3n is combined with Ap micro-phases,the beneficial synergistic effect is obvious.The wear rate of 1Al₂O_3n/10Ap/PFA is one order of magnitude lower than that of 10Ap/PFA,and the friction coefficient is basically unchanged.At this time,although Al₂O_3n also scratches and wears Ap,Ap debris can quickly form a transfer film with uniform structure and easy to spread on the surface of the steel ring due to its easy-to-shear characteristics,and then play a role in reducing friction and wear resistance.3)The rapid formation of the transfer film depends on the cutting action of the nano-phase relative to the PFA and the micro-phase.At the same time,the nano-phase and the micro-phase must possess a favorable synergistic effect so as not to damage the transfer film.During the friction between 1Al₂O_3n/10Ap/PFA and the steel ring,this synergistic effect is manifested in the fact that the PFA molecular chain breaks during the friction process and reacts with O₂ and H₂O in the air to form carboxylic acid end groups,and the carboxylic acid end groups react with the metal surface and the Al₂O_3n released to the interface and chelate to the metal surface to form strong transfer films.SiO_2n has insufficient cutting effect,and the ability to form transfer films is poor,resulting in poor performance of SiO_2n-added composites.4)The micro-nano composite reinforced PFA-based composites 1Al₂O_3n/10Ap/PFA satisfies the conditions for rapid formation of the transfer film and the addition of micro-nano different scales has beneficial synergistic effect,so its wear resistance under different working conditions is significantly better than that of the micro-scale discontinuous reinforced PFA-based composites 10Ap/PFA.