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Chaliampalias D.,Aristotle University of Thessaloniki | Pliatsikas N.,Aristotle University of Thessaloniki | Pavlidou E.,Aristotle University of Thessaloniki | Kolaklieva K.,Central Laboratory of Applied Physics BAS | And 6 more authors.
Surface Engineering | Year: 2016

The thermal stability and the resistance against oxidation of quaternary compositionally gradient CrAlSiN coatings deposited on steel substrate are investigated by examining their structural, morphological and chemical features before and after oxidation tests, as well as by quantitative thermal analysis. The as-deposited samples exhibit a columnar structure, with each column consisting of nanocrystals as fine as 20 nm. The as-deposited coating is mainly composed of CrxAl1−xN solid solution nanocrystals, which are embedded in an amorphous SiNx matrix. When exposed to high-temperature dry air environment the coated samples exhibit remarkable stability as they remained intact up to 800°C. Over 800°C, elements from the substrate outdiffused and modified the chemical content of the film, but still remain oxidation-resistant up to 900°C. © 2016 Institute of Materials, Minerals and Mining

Chaliampalias D.,Aristotle University of Thessaloniki | Kolaklieva L.,Central Laboratory of Applied Physics BAS | Kakanakov R.,Central Laboratory of Applied Physics BAS | Saltidou K.,Aristotle University of Thessaloniki | And 10 more authors.
Journal of Thermal Analysis and Calorimetry | Year: 2015

This work aims to examine the resistance of nanocomposite TiAlSiN gradient films when exposed in high-temperature dry air and 3 % NaCl aqueous solution environments. This was mainly accomplished by thermogravimetric measurements (non-isothermal and isothermal) and potentiodynamic measurements. The thermal analysis results showed that these samples begin to oxidize at 800 °C, while over 900 °C the oxidation rate increases significantly. Isothermal measurements revealed that at 800 °C the mass gain after 12 h exposure is insignificant and at 900 °C it has very low value. Oxidations performed at higher temperatures resulted in elevated mass gain while a great percentage of the coating was transformed in oxides, which implies that the particular temperature range is out of the working limits of the material. The activation energy was also determined to be 200 kJ mol−1 from the thermal analysis outcomes. Finally, the as-coated samples were found to have distinguished corrosion resistance in the salt solution compared with the bare substrates and the commonly used TiN coatings. © 2015 Akadémiai Kiadó, Budapest, Hungary

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