Corrosion behaviour and microstructure of tantalum film on Ti6Al4V substrate by filtered cathodic vacuum arc deposition
Tantalum (Ta) films of about 100 nm in thickness were fabricated onto Ti6Al4V substrate using a filtered cathodic vacuum arc deposition system with and without a − 100 V bias between the substrate and the chamber wall. The structure of the deposited film at zero substrate bias exhibits pure tetragonal phase (beta-Ta), and body-centred cubic structure (alpha-Ta) is found as the substrate bias increased to − 100 V. The film deposited at − 100 V bias shows a significant improvement in cohesion as compared to the film deposited without substrate bias. Potentiodynamic polarization and electrochemical impedance tests in phosphate buffered saline solution revealed that the Ta film at − 100 V bias shows good corrosion resistance with a low corrosion current density of 0.009 μA·cm− 2. The film shows hydrophobic characteristics, low surface free energy and an inert surface presenting a uniform oxide layer, which is promising for potential biomedical implant applications.