Adaptive (Cr,Al)N+Mo:Sg Coating for Highly‐Stressed Contacts under Dry Rolling‐Sliding Conditions

Highly-stressed rolling-sliding contacts under fluid-free lubrication as found in ultralightweight gear applications require effective friction and wear reduction. Promising approaches are PVD deposited Mo:S-modified nitride coatings (Cr,Al)N+Mo:Sg and Zr modified diamond-like-carbon coatings ZrCg that provide transfer film-based self-lubrication. In this study, the self-lubrication mechanism of both systems is tribologically tested on a twin-disk tribometer and physiochemically analyzed by secondary electron microscopy and Raman spectroscopy. MoS2 lacquer provides the reference. Results reveal lowest friction and stable self-lubrication through in-situ MoS2- and MoxOy-rich transfer films from (Cr,Al)N+Mo:Sg on the steel counter surfaces. High pressures and pure rolling conditions favor the transfer film formation. •Low friction and stable operating conditions through (Cr,Al)N+Mo:Sg.•Transfer film from (Cr,Al)N+Mo:Sg is composed of molybdenum disulfide and oxide.•Transfer film enables chemical adaption to tribological conditions.