Researchon Polytetrafluoroethylene Composites Modified With Molybdenum Disulfide And Tungsten Disulfide

Polytetrafluoroethylene has been widely used in all kinds of fields due to its outstanding properties such as excellent chemical stablity, good thermal stability, favorable self-lubricating and so on, however, the application of PTFE is limited due to poor anti-wear ability and mechanical properties.In this paper, polytetrafluoroethylene composites with molybdenum disulfide?MoS₂?and tungsten disulfide?WS₂? as fillers were prepared by powder metallurgy method, the effects of the proportion and content of fillers and operating condition on the frition and wear properties of PTFE composites were systematically investigated. Morphologies of worn surface and transfer film on counterpart balls were observed by SEM and ultra-depth field optical microscopy respectively, in addition, the wear mechanisms were studied.Besides, the physical and mechanical properties were studied. The results are shown as below:?1?Friction and wear experiments were carried out under working load of 50 N and sliding speed of 400r/min, the optimum content is 10% for PTFE/MoS₂ composites, the wear rate of PTFE/10%MoS₂ decreases by 72.7% and friction stability increases by 24.4%compared with pure PTFE. The prime content of PTFE/WS₂ composites is 25%, the friction stability of PTFE/25%WS₂ increases by 24.4% in comparison with neat PTFE.PTFE/25%WS₂ displays better tribology properties than PTFE/10%MoS₂, the wear rate of PTFE/25%WS₂ is 34.5% lower than PTFE/10%MoS₂. PTFE/?10%MoS₂+4%WS₂? exhibits optimal modifiction effect, the wear rate decreases by 36.1% and 2.3% when compared with PTFE/10%MoS₂ and PTFE/25%WS₂ respectively.?2?The results of SEM demonstrat that: worn surfaces of neat PTFE exists big block adhesion substances, adhesive wear is the main wear mechanism. The wear mechanisms of PTFE/MoS₂ composites are adhesive wear first, and then transfer to adhesive and abrasive wear as the increasing of MoS₂ contents, at last accompany with fatigue wear. The main wear mechanisms of PTFE/WS₂ composites are abrasive wear, but adhesive and fatigue spalling also prevail when the content of WS₂ is high. The worn surfaces of PTFE/?10%MoS₂+4%WS₂? are controled by adhesive wear and abrasive wear in combination. The results of ultra-depth field optical microscopy indicate that: the transfer films of PTFE/MoS₂ composites are thick, lumpy and have many defects; in terms of PTFE/WS₂ composites, the transfer films have lots of tiny scratches, and the homogenous and continuity have difference as the diffetent of contents;with regard toPTFE/?10%MoS₂+4%WS₂? composites, the transfer film is thin and uniform.?3?PTFE composites with MoS₂ and/or WS₂ as fillers can not only improve the tribology properties, but also enhance mechanical properties, especially compression performance, the compression strengths are increased by 35%, 22.03% and 28.78% by PTFE/?10%MoS₂+4%WS₂?, PTFE/10% MoS₂ and PTFE/25%WS₂ respectively compared with pure PTFE.?4?The tribilogical behavior of PTFE composites are studied under different operating condition. Friction coefficient of PTFE/10%MoS₂ composite successively increases with the increasing of load and speed; as far as PTFE/25%WS₂ composite, the friction coefficient declines first, and then incerases with the increasing of load and speed;as for PTFE/?10%MoS₂+4%WS₂? composite, the friction coefficient increases with the increasing of load, increases first, and then decreases with the increasing of speed. The friction stability of PTFE/10%MoS₂ and PTFE/25%WS₂ reach best when the load is 50 N and speed is 400r/min, the optimal friction stability of PTFE/?10%MoS₂+4%WS₂?composite is under the load of 30 N and speed of 400r/min. All in all, the lower the load,the smaller the mass loss when the sliding speed remain 400r/min, and the greater the sliding speed, the larger the mass loss when the load remain 50N.