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The aim of the present study is to investigate hydrogen permeation through an aluminium oxide coating Al 2 O 3 , which was deposited on the nanocrystalline titanium (NCTi) using two methods: deposition from a substrate saturated with hydrogen, and saturation of Al 2 O 3 /NCTi system from an ambient medium (electrolyte, gas, plasma). Films were deposited onto the surface of specimens by magnetron sputtering. While performing the deposition, hydrogen diffused throughout the depth of the film; however, diffusion was restricted to the area near the film–substrate interface, affecting less than 50% of the thickness of the film. Film–substrate interface is significantly broader (compared to the deposition on an unsaturated substrate), and metallic hydroxides are formed in the interface. Saturation of Al 2 O 3 /NC Ti system with hydrogen was performed using three methods: electrolytic method, saturation from the high-frequency discharge hydrogen plasma, and from hydrogen atmosphere at high temperature and pressure. The analysis of the saturation process shows that the Al 2 O 3 coating can protect the metal surface from hydrogen permeation only in the case of its operation in the conditions of contact with aqueous solutions.

Titanium nitride, TiN, is used as wear protective and decorative coatings in various applications. These coatings are deposited by standard industrial methods such as chemical and physical vapor deposition (CVD and PVD, respectively), including magnetron sputtering or its modifications [e.g. the plasma-enhanced magnetron sputtered deposition (PMD) method]. The coatings have different microstructures (size and morphology of grains, orientation, dislocation structure, residual stress, etc.) depending on the method used and the deposition regime. The results of comparative transmission electron microscopy (TEM) investigations of the microstructure of thin TiN coatings deposited by classical CVD and PVD, including PMD, are presented. The microstructure was studied in sections perpendicular and parallel to the coating surface. The grain size was estimated from dark field images and the residual stress was determined using the bend extinction contours in the bright field images. It was found that the coatings deposited by PVD and CVD methods have different grain microstructures and residual stresses. The CVD coatings have an equiaxed microcrystalline structure with very low levels of the local residual stress. The mean grain size is 0.4–0.6 μm. The PVD coatings (Balzers and Metaplas) have a non-equilibrium submicron grain structure with a high level of the local residual stress equal to 0.06–0.08E, where E is Young's modulus, and a mean grain size of 0.1–0.2 μm in the section parallel to the coating surface. The PMD coating structure is highly non-equilibrium nanocrystalline, with a very high level of residual stress equal to 0.13E and a much finer grain size of 0.06 μm.