Wear in boundary or mixed lubrication regimes

In order to confirm the recent understanding on wear in boundary or mixed lubrication regimes, the interest of this paper is focused on wear properties of steels in oil. Starting from the confirmation of nine wear modes in mechanical or tribochemical wear, lubricated wear of steels is characterized in relation to lubrication regimes. Typical mechanisms of lubricated wear are explained in the viewpoints of the built-up lump of insoluble wear particles, the extrusion of surface material and tribofilm from contact periphery by plastic flow and the competition between the rate of propagation of a surface fatigue crack and the rate of surface removal by wear. The unique effect of soluble wear particles on running-in of ceramics in water is introduced for comparison.