Influence of roughness parameters on coefficient of friction under lubricated conditions

Surface texture and thus roughness parameters influence coefficient of friction during sliding. In the present investigation, four kinds of surface textures with varying roughness were attained on the steel plate surfaces. The surface textures of the steel plates were characterized in terms of roughness parameter using optical profilometer. Then the pins made of various materials, such as Al-4Mg alloy, Al-8Mg alloy, Cu, Pb, Al, Mg, Zn and Sn were slid against the prepared steel plates using an inclined pin-on-plate sliding tester under lubricated conditions. It was observed that the surface roughness parameter, namely, $R_a$, for different textured surfaces was comparable to one another although they were prepared by different machining techniques. It was also observed that for a given kind of surface texture the coefficient of friction did not vary with $R_a$. However, the coefficient of friction changes considerably with surface textures for similar $R_a$ values for all the materials investigated. Thus, attempts were made to study other surface roughness parameters of the steel plates and correlate them with coefficient of friction.It was observed that among the surface roughness parameters, the mean slope of the profile, Del a( \Delta a), was found to explain the variations best