Phase and roughness analysis of nanocrystalline coatings based on 310S steel with aluminum additions

Aluminum alloying is commonly used to improve its high-temperature oxidation resistance. In this study, Al was incorporated into nanocrystalline coatings produced by magnetron sputtering of 310S chromium-nickel steel. The role of this addition in determining the phase composition and morphology of the coatings, which influence the formation of protective oxide layers under high-temperature conditions, was investigated. The coatings were analyzed using scanning electron microscopy (SEM) and atomic force microscopy (AFM), with emphasis on surface roughness, as well as X-ray diffractometry (XRD) to determine crystallite size and phase composition. It was demonstrated that the addition of aluminum affects phase stability in the coatings. At Al contents of 1-2 at.%, it results in a twofold reduction in the fraction of the fcc phase in the coating (and its disappearance at 5 at.%), along with a similar decrease in surface roughness. At the same time, crystallite size increases while retaining the nanocrystalline structure, creating favorable conditions for the formation of dense Al₂O₃ oxide layers on the coatings.