Keywords: Contact angle; Surface tension; Wetting; CrN/AlN and AlN/CrN coatings; Friction; Hydrophobic and hydrophilic properties; Spreading; Surface energy
This study investigates the influence of the hydrophobic and hydrophilic properties of multilayer coatings deposited on the rubbing surfaces of engine components. Here we investigate the tribological performance of AlN/CrN coatings and a CrN/AlN coating for piston rings. Tribological tests were conducted using a ball-on-disc tribometer. The tribo-tests were performed under a normal load of 5 N, sliding speed of 3.0 m/s, and sliding distance of 1000 m. The topography and morphology of the coatings were analyzed by SEM, EDS and XRD. Moreover, this article also presents the correlations between the angle of action, distribution, surface voltage, and surface energy of coatings, wetted by lube oils and water. The tribological results illustrated that AlN/CrN multilayer coatings (2.3 μm thickness) reduced the friction coefficient by 6%, as compared with CrN/AlN coatings. While the wear rate of AlN/CrN multilayer coatings was increased by 3% compared to reference coating. The tests were carried out under dry friction conditions, surrounded by new oil and surrounded by oil with a 4% content of soot. The novelty of the work is the comparison of the functional properties of anti-wear coatings with strongly hydrophilic or hydrophobic properties during the friction and wear process in laboratory conditions.
