Influence of Nb content on the structure, morphology, nanostructure, and properties of titanium-niobium magnetron sputter deposited coatings for biomedical applications

Abstract Titanium and its alloys are extensively used in biomedical applications due to their adequate mechanical properties, thermal stability, and biocompatibility. In particular, the β stabilized Ti alloys present relatively low elastic modulus compared to other metallic biomaterials and also high strength, low density, high corrosion resistance, and good biocompatibility, making them suitable in hard tissue applications. Niobium is a non-toxic alloying β-stabilizing element that causes a decreasing in the elastic modulus of the Ti alloys without compromising their strength. Stainless steel (SS) has adequate bulk properties to be used as biomaterials for orthopedic and dental implants and is less expensive than Ti alloys, but it is less biocompatible than them; thus we have proposed the use of Ti-Nb alloy thin films as surface coating for SS. Thin films were deposited on AISI 316L SS substrate by magnetron sputtering, and four compositions were produced: Ti 85 Nb 15 (Ti-26 wt% Nb), Ti 80 Nb 20 (Ti-33 wt% Nb), Ti 70 Nb 30 (Ti-45 wt% Nb), and Ti 60 Nb 40 (Ti-56 wt% Nb). The structure, morphology, and nanostructure of the coatings were analyzed by means of x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and the results indicated the formation of the β phase in the coatings for all four compositions. The mechanical properties were assessed by nanoindentation and scratch tests, and the results showed lower elastic modulus values and equal or higher hardness values as compared to commercially used alloys, as well as high values for joint plastic deformation between the coating and substrate.