Caracterização de filmes finos de Nb1-xAlxN depositados por magnetron sputtering em aço inoxidável 316l

Abstract

NbN and Nb1-xAlxN films with 0.10 ≤ x ≤ 0.60 were prepared by reactive magnetron sputtering of Nb and Al targets in an Ar/N2 atmosphere over 316L stainless steel substrates. The films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Films with composition 0 ≤ x ≤ 0.40 presented cubic phase NbN-δ, while x = 0.60 presented AlN-h phase. Electrochemical corrosion resistance was evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization, varying the exposure time to 3.5% NaCl solution up to 30 days. The Al content is related to the corrosion response of the systems, being that films with content (x = 0.40 and 0.60) showed improved protective behavior. The formation of a protective layer of Nb2O5, as confirmed by Raman and XPS measurements, was related to increased corrosion resistance and reduced porosity in the coated systems after 30 days of immersion time in 3.5% (m/v) NaCl solution. Al is also responsible for improvements in terms of oxidation resistance, with oxidation temperatures occurring around 450-600°C for NbN and around 600-750°C for the Nb1-xAlxN films.