Characterization, mechanical and biomedical properties of titanium oxynitride coating

In this study, a titanium oxide-nitride coating was applied to 12Cr18Ni10Ti stainless biomedical steel through reactive magnetron sputtering deposition. The microstructure and chemical bond evolution during film sputtering was tested using different flow rates of oxygen and argon, namely N₂/O₂ ratios of 1, 1.5, and 2. The obtained samples were analysed by IR spectroscopy, SEM, XPS, and XRD. In addition, the nanoindentation procedure measured the hardness and elastic modulus of each coating. Oxynitride coatings exhibit nanocrystalline structures, where the nitride and oxide phases are in the unbound state. A nitrogen-rich sample demonstrated the crystalline structure of (110)-oriented rutile with 124 nm large clusters. However, with increased oxygen gas flow, the mixed rutile-anatase (111)-oriented phase became more pronounced with fragmented grains 25–27 nm in diameter. The nanoindentation test shows that titanium oxide hardness and deformation resistance depend on its microstructure and orientation. Cell culture experiments show that a coating deposited at regime N₂/O₂ = 1 allows efficient cell proliferation on pristine steel and other oxynitride samples. The findings of this work benefit understanding the mechanisms of oxynitride barriers in coronary stent modification.