Tribological Comparison of Coatings Produced by PVD Sputtering for Application on Combustion Piston Rings

This article compares the tribological performance of coatings produced by PVD sputtering. Transition metal dichalcogenide (TMD) coatings doped with carbon (WSC and MoSeC) and nitrogen (WSN and MoSeN) and a conventional diamond-like carbon (DLC) coating are compared. The tribological evaluation was oriented towards the use of coatings on piston rings. Block-on-ring tests in a condition lubricated with an additive-free polyalphaolefin (PAO 8) and at temperatures of 30, 60, and 100 °C were carried out to evaluate the coatings in boundary lubrication conditions. A load scanner test was used to evaluate dry friction and scuffing propensity. In addition to WSN, all other TMD coatings (WSC, MoSeC, and MoSeN) exhibited lower friction than DLC in dry and lubricated conditions. The study reveals that WSC, among TMD coatings, offers promising results, with significantly lower friction levels than DLC, while demonstrating reduced wear and a lower risk of metal adhesion. These findings suggest that WSC may be a viable alternative to DLC in piston rings, with potential benefits for reducing fuel consumption and increasing engine durability.