Tribological solutions for engine piston ring surfaces: an overview on the materials and manufacturing

This paper exhibits an outline of the piston rings operational characteristics and consequently, of their main functional challenges. The basic geometrical shapes, materials and manufacturing technologies used to produce compression rings for up to date diesel engines are summarized. Based on this description, each technological solution to enhance the behavior of the piston rings is fully described and explained. The state-of-the-art solutions such as a DLC (diamond-like carbon) layer, multi-layered coatings and compound coatings are tersely presented and discussed. New approaches suggest surface textures, which are expected to be a major improvement in the development of optimized surface coatings of the piston rings, and the latest progress in that area is examined and debated. Also, a novel solution for the enhancement of the behavior of ring coatings is presented, using a proposed and previously tested solution for a different application. This solution attempts to optimize most of the properties in relation to friction, wear, mechanical stresses, heat dissipation and self-lubrication. The overall idea is to use specific materials in specified positions over the surface to individually enhance the referred properties, creating a multifunctional surface.