Study On Tribological Properties Of PTFE And PEEK-based Composite Materials

In this thesis,the tribology and wear mechanism of PTFE and PEEK-based polymers with different metals and ceramics under dry friction and seawater conditions are studied.The mechanism of the sliding speed on its friction and wear performance was discussed.It mainly analyzes the effects of internal factors(different polymer fillers)and external factors(different friction conditions and matching)on the tribology of polymer materials.The purpose is to explore the coupling effect of internal and external factors on the tribological properties of PTFE-based composites and PEEK-based polymers.In this thesis,a vertical universal friction and wear tester is used to perform pin-disk friction and wear experiments,and the morphology and phase composition of the friction surface are analyzed by means of scanning electron microscope,X-ray electron spectrometer and other testing methods.The research results obtained in this thesis are as follows:(1)Under dry friction conditions,the PTFE-based composites were paired with stainless steel 2507,aluminum alloy 6061,and Si3N4 ceramics,respectively,and the friction and wear performances at different speeds were studied.The results show that in the dry friction environment,the friction factors of the PTFE-based composite materials and the three types of mating materials are directly proportional to the speed,the friction factors all show an upward trend with the increase of the speed.On the whole,under the condition of dry friction,the lower friction coefficient and wear rate obtained by the PTFE-based composite material/aluminum alloy 6061 pair have good tribological properties.Especially at a speed of 300r/min,the friction factor is as low as 0.138,and the pin and disk wear rates are as low as 10-5 orders of magnitude.The wear mechanism is mainly based on slight abrasive wear and adhesive wear.(2)Under seawater environment,PTFE,CF-PTFE,and GF-PTFE are paired with Si3N4 ceramics to study friction at different speeds wear performance.The research shows that with the increase of speed,the friction pairs all show a trend of better tribological characteristics.Among them,the friction coefficient of CF-PTFE/Si3N4 ceramic pairing at a speed of 1000r/min is as low as 0.026,and the order of the wear rate of the pins and disks matching it is as low as 10-5.In the seawater environment,the friction pair surface is accompanied by a friction chemical reaction during the friction process.The generated oxide and hydroxide form a lubricating film on the friction surface,which has a certain protection and lubrication effect.On the other hand,in the friction experiment,the seawater medium will wash away some of the abrasive grains,which inhibits the abrasive grain wear to a certain extent.The wear mechanism of the friction pair is mainly slight abrasive wear and chemical wear.On the whole,CF-PTFE/Si3N4 ceramic pairings have the lowest friction coefficient and good tribological properties under seawater environment.Compared with glass fibers,carbon fibers can better improve the tribological properties of composite materials.(3)Under dry friction conditions,PEEK materials were paired with stainless steel 2507,aluminum alloy 6061,and Si3N4 ceramics,respectively,and their friction and wear performance at different speeds were studied.The results show that as the sliding speed increases,the friction factors of the friction pairs all show an upward trend.On the whole,under different sliding speeds of dry friction,the friction coefficient obtained by PEEK/aluminum alloy 6061 pair is better overall,and has better tribological performance.Especially at a sliding speed of 300r/min,a friction factor of 0.291 is obtained,and the pin and disk wear rates are as low as 10-5 orders of magnitude.The main wear mechanism of friction pair is abrasive wear and adhesive wear.(4)Under seawater environment,PEEK,CF-PEEK(carbon fiber reinforced polyetheretherketone)and GF-PEEK(glass fiber reinforced polyetheretherketone)are paired with Si3N4 ceramics respectively to study the friction and wear performance at different sliding speeds.The results show that with increasing speed,the tribological characteristics of the friction pairs are improved.Overall,in the seawater environment,the CF-PEEK/Si3N4 ceramic pair has the lowest friction factor and has good tribological properties.Especially at the sliding friction speed of 1000r/min,the friction factor of CF-PEEK/Si3N4 ceramic pair is as low as 0.026,and the wear rate of pins and disks is as low as 10-6 orders of magnitude.In the seawater environment,the friction chemical reaction exists on the surface of the friction pair.The friction chemical reaction product has a certain lubricating effect.At the same time,the Ca2+and Mg2+ions in the seawater contribute to the morphological aggregation of the reaction products and have a lubricating protection effect Smooth surface film.On the other hand,in the friction experiment,the seawater medium will also take away some abrasive particles,weakening the degree of abrasive wear.(5)By comparing the tribological properties of two typical polymers,it is found that under dry friction conditions,compared with two typical polymer composites of PTFE and PEEK,PTFE-based composites show better tribological properties at different speeds.Compared with the three matching materials,aluminum alloy 6061 shows better tribological properties.The pairing of PTFE and aluminum alloy 6061 is more suitable as the pairing material of piston ring material of small oil-free air compressor.Under seawater environment,the carbon fiber toughened polymer and Si3N4 ceramic friction pair show better tribological properties at different speeds overall.Carbon fiber can improve the tribological properties of composite materials under seawater environment more than glass fiber.On the whole,CF-PTFE/Si3N4 ceramic pair has better tribological characteristics,showing lower friction factor and wear rate.The research in this thesis shows the friction and wear characteristics of PTFE-based composites,PEEK-based composites,and metal and ceramic materials under different environments and conditions,respectively.Under dry friction conditions,the pair of PTFE-based composite material/6061 aluminum alloy material is suitable as a pair of small oil-free air compressor piston ring materials.In the seawater environment,CF-PTFE/Si3N4 shows better tribological properties as a whole.This not only enriches the choice of friction pairing materials under dry friction conditions and marine environments,but also provides theoretical support for the research and application of tribological properties of friction pairs under these two conditions.