The Influences Of Metal Counterface Topography On The Friction Wear And Transfer Film Of PTFE-Alumina

Polymers are widely used as self-lubricating materials in engineering.Neat polymers often lack sufficient lubricity or wear resistance,so fillers are used to reinforce the polymer and improve its performance under sliding conditions.When tribological polymers composites slide against a metallic counterface,the resulting wear debris tend to mechanically or chemically adhere to the counterface to form a protective transfer film.The improvements in tribological properties for polymer composites are widely attributed to the quality of these transfer films on metal surface.Previous studies have shown that the metal surface has a significant influence on the friction between the interfaces when the polymer works with the metal.An ultra-low wear(k¹0^-7 mm³/Nm)alumina-PTFE solid lubricant loses wear resistance and the ability to form stable transfer films when the surface roughness exceeds a critical magnitude or aligns with the sliding direction.In order to further explore the effects of surface topography on the wear and transfer process of PTFE/Al₂O₃ composite materials,a series of control roughness peaks valleys,surface skewness and unidirectional texture were selected and friction and wear experiments were carried outFirstly,counterfaces with different surface roughness and removed peak and different skewered are prepared on 304 stainless steel.Unidirectional micro-textures with different spacing and depth are prepared on the Fiber Laser Marking Machine.The three dimensional surface topography of metal surface before tests were measured by white light interference profiler and S_a,S_sk,S_v and S_p were selected to characterize the surface morphology of the sample.Then,the friction experiments were conducted under dry friction condition by using the tailored friction tester.Finally,high frequency interrupted microscopy measurements were used to record the details of debris and transfer film engagement,migration,aggregation,and removal.The experimental results show that the surface roughness has little effect on the friction coefficient,steady state wear rate and transfer film quality of polymer.On rough surfaces with tall peaks,the composite eventually achieved ultra-low wear by gradually removing the tallest asperities to achieve a more favorable topography for transfer film formation,however,the formation process of the transfer film is different,the seed mode is grown on the smooth region and the growth in the groove.Preferential removal of the tallest peaks on the counterface helped stabilize the transfer films and dramatically reduced the transient wear volume of the polymer composite even on very rough surfaces.Intersecting valleys and smooth plateaus helped nucleate and stabilize transfer films.The surface texture of different depth and spacing shows different friction and wear performances and form the different morphology transfer film.When the transfer film formed in the micro-groove,the polymer reaches ultra-low wear(10^-8 mm³/Nm).