Self-organized TiO2 nanotubes on Ti-Nb-Fe alloys for biomedical applications: Synthesis and characterization

•The effect of Fe addition on the formation and crystallization of TiO2 nanotubes on Ti-30Nb-xFe substrates were investigated.•Fe-addition favors the formation of TiO2 nanotubes with a bimodal size distribution and decreases the thickness nanostructured layer.•Crystallization of nanotubes to the anatase phase occur at lower temperatures for samples without Fe addition.•The crystalline TiO2 nanotubes formed on Ti-30Nb-3Fe substrate exhibit greater cell viability.