Oil-impregnated sintered bearings are widely used in various products. Friction reduction in them is still a large target for the related industries. In those bearings, lubricating oil exudes from the porous bearing body and lubricates the shaft and bearing surfaces. However, the amount of oil in those sliding areas is often insufficient leading to an unsatisfactory friction. Oil wettability of the shaft surfaces was found to have a large effect on the friction of those bearings. Low oil-wettable shaft could retain a larger amount of oil in the bearing clearances and indicated lower friction than highly wettable shaft. This is because a large contact-angle hysteresis between the oil and the low-wettable shaft surface allows the retention of large oil droplets in the bearing clearances. The control of oil-wettability of the shaft surface could be an effective means of reducing friction for oil-impregnated sintered bearings.
Part of the book: Wettability and Interfacial Phenomena