The Effects of Dimple Size and Depth on Friction Reduction Under Boundary Lubrication Pressure

The effect of dimple size on sliding friction conducted under boundary lubrication conditions using a four-ball wear tester was investigated. The contact geometry used was a ball-on-three-flats arrangement using 52100 steel balls and flats. Circular dimples of various diameters (20–60 μm) and depth (2.5–10 μm) were fabricated using micro-lithography followed by electrochemical etching. Tests were conducted from 98–296N loads and 0.2–1.3 m/s speeds. Results suggest that smaller dimples with shallower depth achieve higher level of friction reduction under these test conditions.