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

TL;DR

This study uses first principles calculations to explore how water molecules and hydrogen interact with CrN/TiN multilayer coatings, revealing a water-based nanobearing effect that influences their friction properties in different humidity conditions.

Contribution

It introduces a first principles approach to understanding water-based self-assembled nanobearing effects in CrN/TiN multilayer coatings, linking atomic interactions to tribological behavior.

Findings

Hydrogen diffuses more easily on TiN(001) than on CrN(001).

Both TiN and CrN strongly bond with O and H adatoms.

Proposed mechanism explains humidity-dependent friction behavior.

Abstract

Recently, we have reported on low friction CrN/TiN coatings deposited using a hybrid sputtering technique. These multilayers exhibit friction coefficients $\mu$ below 0.1 when tested in atmosphere with a relative humidity $\approx25%$, but $\mu$ 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.