Tribological behaviour of alternative surface modifications for cold rolling mill rolls

Abstract

The present work used a new methodology proposed in previous work to analyse the tribological behaviour of coatings/surface modifications with potential to replace the carcinogenic hard chrome still applied in the rolls employed in cold rolling mills. For that, three surface modifications (chromium plating, electroless NiP coating, and plasma nitriding) were carried out on specimens that were previously either ground or surface textured by electrical discharge texturing. The specimens with electroless NiP coating presented the lowest friction coefficients, while plasma nitrided specimens showed the highest. A tribolayer rich in Nickel, Phosphorus, and Oxygen was found for the samples with electroless NiP coating on the surfaces of both the specimens and the counter-bodies, which was apparently responsible for providing low and stable friction coefficient values, as well as reduced wear rates.