Oil-in-water(O/W) emulsions are widely used in metal working such as hot rolling and cutting.Three kinds of O/W emulsions with low oil concentration were prepared which include conventional emulsion(CE),miniemulsion(MNE) and microemulsion(ME).The lubricating properties of O/W emulsions with low oil concentration were investigated using the tribological testers and the thin film interferometry based on the relative optical interference intensity method.The tribological test results under boundary lubrication show that the friction coefficient and the total losing weight can be clearly seen:CE < MNE < ME.The lubricating film thicknesses under elastohydrodynamic lubrication and thin film lubrication show that a relationship of the film formation abilities:CE > MNE > ME.Competitive wetting behavior of water and oil on solid surface was confirmed to play an important role in the film formation and tribological behaviors of O/W emulsion.
