Efficiency of laser surface texturing in the reduction of friction under mixed lubrication

The tribological behavior of steel sliding pairs with dimples ranging from 15 to 800 m in diameter was characterized in the mixed lubrication regime in a pin-on-disk experiment. The pin was textured, keeping the total dimpled area constant at 10% and the depth-to-diameter ratio at 0.1. Polyalphaolefin (PAO) was used as a model lubricant. Experiments were carried out under unidirectional sliding conditions at 50 and 100 °C. At constant depth-to-diameter ratio the results showed a significant non-linear dependence of the friction coefficient on the texture diameter, sliding speed and the oil temperature (viscosity). A friction reduction of up to 80% was possible with the optimal diameter for certain sliding speeds. The dimple diameters leading to the highest friction reduction significantly depend on the oil temperature. By reducing the oil temperature from 100 to 50°C the dimple diameter resulting in the highest friction reduction changed from 40 to 200 µm.