1.At high load,there exists a strong solid–liquid inter action in steel-[Bmim][PF6] interface by tribochemical reactions.
(2) Surface deformation occurred on PEEK and steel surface led to
lower solid roughness.
(3) The viscosity of [Bmim][PF6] keeps high for low friction heat.
(4) For(1)–(3), [Bmim][PF6] lubricated PEEK/steel slide can carry high load,the slide falls in hydrodynamic lubrication and elastohydrodynamiclubricationregionunder150–1500N.
Low friction coefficient of 0.016 and negligible wear were observed at 1500N.