Evaluation of piston ring materials in oil containing an abrasive using a ring-on-block test machine

To evaluate the wear resistance of hard piston ring coatings, a piston ring segment test was developed. Using a conventional ring-on-block test machine, the specimen-holding system was modified to allow a coated piston ring segment to be progressively worn against an oscillating sintered tungsten carbide test ring in uncontaminated and abrasive contaminated oil. An analysis of the worn volume of such a test was performed, and the resulting wear rates correlated well with previously conducted pin-on-disk tests. It was found that tungsten carbide plasma coatings deposited by several fabricators showed similar wear behavior and were relatively unaffected by the abrasive contaminant. In contrast, commercially available chromium plated coatings and a Cr 2C 3-based coating were adversely affected by the contaminant.