First principles study of water-based self-assembled nanobearing effect in CrN/TiN multilayer coatings

Abstract

Recently, we have reported on low friction CrN/TiN coatings deposited using a hybrid sputtering technique. These multilayers exhibit friction coefficients μ below 0.1 when tested in atmosphere with a relative humidity ≈ 25%, but μ ranges between 0.6–0.8 upon decreasing the humidity below 5%. Here we use first principle calculations to study O and H adatom energetics on TiN and CrN (001) surfaces. The diffusional barrier of H on TiN (001) is about half of the value on CrN (001) surface, while both elements are stronger bonded on CrN. Based on these results we propose a mechanism for a water-based self-assembled nanobearing.