Understanding the role of surface textures in improving the performance of boundary additives, part I: Experimental

Tribological performance of systems in boundary lubrication is dependent on contact and lubricant conditions such as temperature, lubricant additive concentration, surface characteristics, contact pressure and additive-additive interactions. Although past parametric studies have investigated these various factors, there are limited studies on the effect of surface topography on the performance of boundary lubrication additives. This is pertinent because of the increased use of surface texturing in lubricated contacts. This study has employed laser surface texturing to achieve surfaces with different topographies. The influence of the different surface topographies on the tribological performance of a friction modifier additive, molybdenum dialkyldithiocarbamate (MoDTC), was investigated. Results show that laser-textured surfaces in some instances can offer improved friction performance compared to non-textured (polished) surfaces when working positively with a friction modifier additive. Anisotropic surfaces resulted in improved friction. The mechanism for the improved performance of the laser-textured surfaces is believed to be through the augmented local contact pressures at the asperities that accelerate additive decomposition to form protective low-friction tribofilms. This study demonstrates the feasibility of surface texturing in improving the performance of boundary additives.