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.
Highlights
Chromium and titanium nitride (CrN, TiN) thin films are widely used as hard protective coatings for various industrial and automotive applications as they show high hardness and increased wear and corrosion resistance [1,2,3,4,5,6]
In this paper we report on density functional theory (DFT) calculation of the hydrogen and oxygen adatom interactions with the free CrN and TiN surfaces, as a first approach to the complex interaction between the water molecule and multilayer system
The lowest energy barrier for the surface diffusion of O on the TiN surface is ≈ 0.8 eV, corresponding to a movement along the directions, suggesting a zig-zag movement between Ti sites and avoiding N sites
Summary
Chromium and titanium nitride (CrN, TiN) thin films are widely used as hard protective coatings for various industrial and automotive applications as they show high hardness and increased wear and corrosion resistance [1,2,3,4,5,6]. Tribological investigations of such coatings indicate that the coefficient of friction μ, is around 0.45 and 0.8 for CrN and TiN coatings, respectively [7,8,9,10,11]. The resulting films indicate a dense superlattice structure with a bilayer period λ from 6 to
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