Friction reduction and anti-wear mechanisms of surface-textured graphite under water lubrication

Abstract

In this study, tribological behaviors of surface-textured graphite samples under water lubrication are analyzed by experiments and molecular dynamics simulations to reveal the underlying friction and anti-wear mechanism. Circular dimple-type textures are chosen for investigations. Ball-on-disc frictional tests are performed to investigate the influence of texture spacing on friction coefficient and wear degree. The sample with a texture spacing of 200 μm possesses the lowest friction coefficients and the smallest cross-sectional area of the wear mark. The roles of support strength of solid part among textures, water wettability and water film in determining the water-lubricated tribological behaviors are analyzed in detail. The water molecules trapped by the dimple-type textures can produce additional hydrostatic pressure, which is the most crucial factor. The results of this study can guide the design of water-lubricated graphite components with surface textures, such as mechanical seals and graphite bearings in nuclear main pumps and ships.