Tribological Behavior of Multi-scaled Patterned Surfaces Machined Through Inclined End Milling and Micro Shot Blasting

Surface texturing is one mechanism that friction coefficients in both dry and lubricated contacts can be reduced compared with untextured, flat surfaces. End milling and shot blasting are two processes used to produce surface textures, including monolithic textures that have one type of surface feature, as well as multi-scale roughness features when two texturing processes are sequentially used. In such surfaces, we have observed that surface texturing decreases the measured friction coefficient under lubricated conditions, and that greater reductions in the friction coefficient are observed for those surfaces that had been both end milled and shot blasted. Simulations replicating the experiments suggest that the greatest factor contributing to the reduced friction observed for the textured surfaces is a result of increased fluid pressure in the contact region resulting from cavitation of the lubricant. However, a substantial decrease in the depth of the dimples on worn surfaces was also observed, suggesting that entrapment of wear particles within the surface texture features may also influence the measured friction coefficient. Alongside friction measurements, analysis of the wear track depth showed that surface texturing also has a beneficial influence on the calculated Archard wear coefficient.