Influence of different rhombic surface textures on the tribological performance of water-lubricated bearings

Water lubrication has gradually replaced oil lubrication for a wide range of marine stern bearings. However, due to poor water carrying capacity, the tribological performances of water lubricated bearings can be improved by incorporating surface textures. In this work, rhombic textured thermoplastic polyurethane (TPU) specimens, 3D-printed with different heights/depths, 1 mm bulge, 0.5 mm bulge, 0.5 mm dimple, and 1 mm dimple, were tested for their tribological performances when they were lubricated by water and were compared to nontextured specimens. The friction coefficient, wear mass, and microscopic surface topography of the specimens were collected at a common working load (0.4 MPa) and speed (from 50 to 350 rpm), and at low-speed and heavy load (50 rpm and 0.8 MPa) conditions. Experimental results reflect that the rhombic surface texture can effectively improve the friction and wear performances of TPU materials. The friction coefficients of most textured specimens are smaller than those of non-textured specimens under various working conditions. The surface wear conditions of all textured specimens are superior to non-textured specimens, since the rhombic surface texture produces additional hydrodynamic lubrication by creating converge and cavitation effects and prevents abrasive particles from accumulating on the friction surface. Through experimental demonstration, the 1 mm bulge rhombic texture is the best of all the tested textured specimens. This finding can provide a reference for practical industrial applications.