Study Of The Effect Of Surface Topography On Tribological Behavior Of PTFE

As a high-performance polymer materials,PTFE has good self-lubricating properties and high temperature stability.Therefore,this material is often used as a tribological component,and it's widely used in engineering machinery such as the sealing and transmission.With the continuous development of these fields,higher requirements are put forward on the power consumption and service life of PTFE,so it is of great significance to improve the friction and wear of PTFE.Taking PTFE/stainless steel as the research object,the purpose of this paper is to explore the effect of contacting surface morphology on tribological behavior of PTFE,which is aimed at improving the tribological properties of PTFE by reasonable design of the contacting surface morphology.Firstly,the surface roughness of stainless steel is controlled by sandpapers of different grits,and the effect of surface roughness on PTFE friction and wear properties under dry and water lubrication was studied.Then,making sure that the original surface roughness of stainless steel is about 20 nm,the texture is further fabricated on its surface,and the effect of the surface texture on the tribological properties of PTFE under water lubrication is explored.The main conclusions of this paper are as follows:(1)Under dry friction,the transfer film is an important factor affecting the tribological behavior of PTFE.At the load of 0.5N,the surface is not covered with a uniform transfer film.Therefore,the friction coefficient and wear rate of PTFE depend on the combined effect of intermolecular force and mechanical action.Thus there exists an optimal Ra which could make the tribological properties best,here Ra about 60 nm.At a higher load of 2N,a complete transfer film is formed on the sliding track,and the friction is changed to the friction between the PTFE molecules,resulting in the friction coefficient being hardly affected by the surface roughness;the rougher the surface,the stronger the blingding force between transfer film and the surface.As a rusult,the rougher the surface,the lower the wear rate of PTFE.(2)Under water lubrication,the water played a major role in the boundary lubrication and cooling the interface,and inhibiting the transfer film formation.At the load of 0.5 N,the friction interface is well lubricated.The sharpness of the roughness peak is the dominant factor affecting the friction and wear of PTFE.Therefore,the friction coefficient and the wear rate increase with the increase of the surface roughness and they both obtain the lowest values when Ra is 60 nm.At a higher load of 2N,the a smooth surface(Ra 20nm)can store a certain lubricant,but the water is further extruded under higher pressure which provide insufficient lubrication at the friction interface,resulting in severe friction and wear.Therefore,the tribological behavior of PTFE is excellent when Ra is 60 nm.(3)Under water lubrication,there exists appropriate texture parameters whicn can reduce friction coefficient,in this case d = 200?m and r = 20%.The anti-friction effect of this surface texture is excellent,even the friction decreased by 72.8% at a speed of 50mm/s.At this texture parameter,when the speed is less than 30mm/s,surface texture causes higher wear rate of PTFE because the surface texture is able to storage debris and cut the counterpart;when the speed is higher,the hydrodynamic lubricating effect of the surface texture is remarkable and the wear rate of PTFE decreases by 40.5% compared with non-textured surface.