Density-gradient surface textures on cylinder liners for tribological performance improvement via precision electrolytic etching processes

Abstract Abstract：As an effective approach for enhancing the tribological properties of cylinder liner-piston rings (CL-PRs) in diesel engines, surface texturing has garnered significant attention. Precision electrolytic etching emerged as a particularly promising technique, offering precise control over feature geometry and density for surface texturing. Recent engine bench tests demonstrated significant fuel efficiency gains using electrolytically etched high-density textures on cylinder liners, with an unclear underlying mechanism. Therefore, this study prepared zoned textures on CL-PRs with high density based on the results from engine engineering tests via electrolytic etching. Subsequently, a series of tribological tests were conducted on a reciprocating friction testing machine named MWF-10 at applied loads of 200 N, 400 N, and 600 N with reciprocating speeds of 100 r/min and 200 r/min. Each test group ran continuously for 2 hours, yielding parameters such as friction coefficient, morphology of the worn surface, wear particles in the oil, and vibration signals. The results indicated that the friction coefficient of the zoned-texture CL-PR with high density was reduced by up to 31.4%, with notable improvements in wear and vibration performance. Specifically, the high-density large pits in the zoned texture significantly enhanced the oil storage capacity, while the small pits contribute to improving the hydrodynamic lubrication effects of the friction pair. Consequently, the precise feature control to the electrolytic etching process enabled substantial improvement in the overall tribological properties of the CL-PRs.