In Vitro Corrosion of Titanium Nitride and Oxynitride-Based Biocompatible Coatings Deposited on Stainless Steel

The reactive cathodic arc deposition technique was used to produce Ti nitride and oxynitride coatings on 304 stainless steel substrates (SS). Both mono (SS/TiN, SS/TiNO) and bilayer coatings (SS/TiN/TiNO and SS/TiNO/TiN) were investigated in terms of elemental and phase composition, microstructure, grain size, morphology, and roughness. The corrosion behavior in a solution consisting of 0.10 M NaCl + 1.96 M H2O2 was evaluated, aiming for biomedical applications. The results showed that the coatings were compact, homogeneously deposited on the substrate, and displaying rough surfaces. The XRD analysis indicated that both mono and bilayer coatings showed only cubic phases with (111) and (222) preferred orientations. The highest crystallinity was shown by the SS/TiN coating, as indicated also by the largest grain size of 23.8 nm, which progressively decreased to 16.3 nm for the SS/TiNO monolayer. The oxynitride layers exhibited the best in vitro corrosion resistance either as a monolayer or as a top layer in the bilayer structure, making them a good candidate for implant applications.

AES CHARACTERIZATION OF CONSTITUENTS’ OXIDATION STATE IN SPECTRALLY SELECTIVE TITANIUM-OXYNITRIDE COATINGS ON METALS FOR HIGH EFFICIENT SOLAR ABSORBERS

In this study, a surface-sensitive Auger Electron Spectroscopy (AES) was used to comprehensively characterize titanium-oxynitride coatings on metals for high efficient solar absorbers. Primary information obtained from the AES is chemical composition, but chemical state of the elements may also be estimated. Corroborative information about the coating’s structure was obtained from the estimate of Cu, Al and Ti oxidation state vs depth, also derived from the AES data. Ti/(O [Formula: see text] N) concentration ratios vs depth in TiOXNY layer of the coatings on the Al and Cu substrate were also determined. Physical Vapor Deposition (PVD) was used to prepare TiOXNY multilayered on Al and Cu substrates. Individual layer’s depth was in submicron domain. Deposition procedure and corresponding deposition parameters are presented. Optical properties (emittance, absorptance) of the coatings on both substrate types were also measured to confirm that coatings performed well their intended function (i.e. spectral selectivity).