Formation of metalF bonds during frictional sliding: Influence of water and applied load

•This work proves the effect of water lubrication and normal load on the formation of PTFE transfer films.•This work identifies metalF bonds during sliding when PTFE filled composites sliding against steel and Al2O3 balls.•This work explains the formation of PTFE transfer film under various sliding conditions.

Effects of water lubrication and applied load on the formation of PTFE transfer films and metalF bonds during sliding when PTFE filled composites sliding against steel and Al2O3 are investigated. In water-lubricated conditions, XPS analysis reveals that a thin layer of water molecules at the sliding interface inhibits the formation of PTFE transfer films and AlF bonds on the Al2O3 ball, leading to a detrimental effect on the tribo-performance. Under various normal loads in dry sliding condition, it is found that the smearing of PTFE onto the wear surface of the composite and the transfer of PTFE onto the surface of the steel counterpart are stimulated by a high load. During sliding, the contact pressure is found to be the driving force of the reaction between steel and PTFE. It is concluded that under various loads, the total amount of PTFE transfer films has a larger impact on the friction behavior than the formation of FeF bonds.

Graphical abstractDownload high-res image (362KB)Download full-size image