Research On Polytetrafluoroethylene Composites Modified With Bronze And Boron Carbide

Polytetrafluoroethylene(PTFE)has been widely used in all kinds of fields due to its outstanding properties such as excellent chemical stability,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 bronze,boron carbide(B₄C)and bronze/B₄C composite as fillers were prepared by powder metallurgy method,the effects of the proportion and content of fillers and operating condition on the friction and wear properties of PTFE composites were systematically investigated.Morphologies of worn surface of PTFE composites and counterpart balls were observed by SEM and ultra-depth field optical microscopy respectively,in addition,the wear mechanisms of PTFE composites were studied.Besides,the physical and mechanical properties PTFE composites were studied.The results are shown as below:1.In this paper,the density and hardness of the PTFE composites increase with the increasing of the proportions of different fillers,the compression strengths of PTFE composites increase first and then decline with the increasing of the proportions of different fillers.2.PTFE composites with Bronze and/or B₄C as fillers improve the physical and mechanical properties,especially the compression performance,the compression strengths are increased by 60.7%,48.2%,and 36.4%by 30%Bronze/PTFE,9%B₄C/PTFE and(12%Bronze+6%B₄C)/PTFE respectively compared with pure PTFE.3.Friction and wear experiments were carried out under working load of 30N,sliding speed of 300r/min and sliding time of 60min,the optimum composition is 30%bronze for bronze/PTFE composites,the optimal composition is 6%B₄C for B₄C/PTFE composites,the optimal composition is 12%bronze+6%B₄C for bronze/B₄C/PTFE composites.4.Observing the worn surface of single-filled optimal components and composite-filled optimal components and their counterpart balls by SEM and ultra-depth field optical microscopy respectively.It is found that the main wear mechanisms of single-filled optimal components are adhesive wear,and the main wear mechanism of composite-filled optimal components is abrasive wear.5.In this paper,the friction coefficients of the 30%bronze/PTFE composites,6%B₄C/PTFE composites and(12%bronze+6%B₄C)/PTFE composites decrease first and then increase with the increasing of load,and their wear rates increase with increasing of the load.The friction coefficients of the 30%bronze/PTFE composites,6%B₄C/PTFE composites and(12%bronze+6%B₄C)/PTFE composites decrease with increasing of speed,and their wear rates increase with increasing of the speed.6.Observing the morphologies of worn surfaces of PTFE composites and counterpart balls under different working load and sliding speed,it is found that the working load and sliding speed affect the friction and wear properties of PTFE composites by changing the surface temperature of friction pair.The main wear mechanisms of these composites are adhesion wear.