Development of tantalum oxide (Ta-O) thin film coating on biomedical Ti-6Al-4V alloy to enhance mechanical properties and biocompatibility

Ti-6Al-4V is widely used for arthroprostheses, particularly in metal-on-metal (MoM) hip joints. In spite of the suitable wear and corrosion resistance, metallic wear particles and metal ion release occur on a large timescale. In addition, metal ion levels in patients' blood and urine often reportedly increase according to clinical data. Neurological disease, inflammatory response and cell necrosis can potentially develop consequently. The aim of this research is to fabricate a thin, hard film coating on Ti-6Al-4V in order to improve mechanical properties, such as the adhesion strength, surface hardness and surface roughness of Ti-6Al-4V, which should lead to substrate biocompatibility mitigation through reduced debris production, ion release and cytotoxicity. Physical vapor deposition (PVD) magnetron sputtering treatment is applied to obtain an enriched tantalum oxide (Ta-O) thin film coating. In this regard, pure tantalum (Ta) as a biocompatible metal is deposited atop Ti-6Al-4V substrate in the presence of oxygen gas and different parameter conditions, including substrate temperature, argon flow rate, oxygen flow rate and DC power. The results indicate that the surface hardness and surface roughness of the Ta-O coated substrate significantly improve compared to uncoated substrate. The adhesion strength between Ta-O thin film and substrate is examined using a micro scratch tester, and maximum adhesion of 2500 mN is achieved.