Electrochemical and biological properties of mono- and bilayer nitride coatings deposited on Ti–6%Al–4%V alloy

Abstract

Mono- and bilayer coatings were deposited by plasma nitriding process, cathodic plasma electrolytic deposition, and cathodic arc evaporation methods to improve the corrosion resistance and biological properties of the Ti–6Al–4V substrate. Coatings characterizations include phase analysis, surface morphology, and film microstructure observations were done using X-ray diffraction (XRD) analysis, atomic force microscope, and field emission scanning electron microscopy (FESEM), respectively. The results confirmed the formation of titanium nitride phases (TiN and Ti2N) in plasma nitriding and cathodic arc evaporation processes and deposition of oxy-nitride phases (TiNxOy) in plasma electrolytic nitriding process. The electrochemical study of coated and uncoated samples in a simulated body fluid (SBF) solution revealed the lower corrosion current density for bilayer nitride coating in comparison to the monolayer coating and substrate. Lower penetration of solution and more stable phases such as TiO2 improved the corrosion resistance of bilayer coatings. Hemocompatibility and MTT assay were performed on the coated and uncoated sample to determine the blood compatibility and cell viability. The statistical results showed better cell growth on the bilayer nitride coatings after three days.