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The paper deals with evaluation of PVD functionally graded coatings based on Cr-Al-N, TiN and Ti-Al-N. Coatings were deposited in the following combinations: CrAl/CrAlN, Cr/CrN/CrAlN, nitriding/Cr/CrN/CrAlN, nitriding/TiN/AlTiN and nitriding/AlTi/AlTiN. As main criteria for coatings properties and quality comparison methods of scratch test and nanohardness measurement were selected. Subsequently, coatings CrAlN and TiN were designed as protection against high temperature oxidation of Cr-Ni steel (X16CrNiSi25-20) exposed to the temperature of 850 °C for 6 and 12 hours duration. Detailed microstructural analysis of the coating - substrate interface including EDS microanalysis of the elements distribution in the coating and the substrate was performed. Scratch test of selected coating after heat exposure was carried out in order to determine adhesion. From simulated tests it is evident that PVD coating CrAlN fulfils the role of protection. In the case of TiN there occurred intensive subsurface degradation of the coating connected with decohesion and subsequent cracking off the coating.
Keywords: PVD coating, FGM, CrNi austenitic steel, heat load, CrAlN© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.