Influence of crystal grain structure of steel surface on formation of chemical reaction film derived from engine oil additives

This study investigated the relationship between the chemical reaction film formation derived from engine oil additives and crystal grain structure of a steel surface. Variations in the contact area between a rotating sapphire disc and a stationary steel pin were captured by a monochromatic high-speed camera. A fully formulated low viscosity engine oil was used as the lubricant. After friction tests, the elements on the surface were analysed using energy dispersive X-ray spectroscopy and the crystal grain structure of the top surface layer by electron backscatter diffraction. In-situ and ex-situ analyses revealed that plastic flow changed the crystal grain structure of the surface, inhibiting the formation of the chemical reaction film derived from additives.