12. Influence of Surface Texturing on Friction and Wear

The chapter highlights the investigations on the friction reduction capability of a pre-determined sized hemispherical dimples of 3 mm diameter, taking into consideration the fact of easy availability of the tool (ball nose end mill) for industrial applications. The dimples were created using CNC milling machines on EN 31 disc. A pin-on-disc tribometer was used to investigate the tribological behavior of the various textured density surface (7.5, 15 and 22.5%) against EN 8 steel under various loading conditions (120, 140, and 160 N) and very harsh lubricating conditions: dry, partial lubrication (lubricant supplied 54 mL dropwise at a flowrate 1 mL/s) and starved lubrication (10 mL lubricant spread over the disc before the experiment). A significant decrease of 12% reduction of coefficient of friction (COF) was observed with 15% texture density under 120 N while the COF increased by 40–60% at texture density of 22.5% and high loads. In dry condition there was no significant change in COF but the specific wear rate decreased by 64.69% in 22.5% texture density. In the present set of experiments carried out at lighter load (120 N), both 7.5 and 15% texture densities exhibited better results as compared to 22.5% texture densities (under partial lubrication). Surface characterizations by optical microscopy revealed that the friction reduction of the dimpled surface was primarily due to the lubricant retaining capability by the dimples which acted as oil reservoirs, but high texture densities intensified the friction.