Functionally graded HA-TiO₂ nanostructured composite coating on Ti-6Al-4V substrate via electrophoretic deposition

In the present study, electrophoretic deposition was carried out in the ethanol-based suspensions at the voltage of 20V for 3min to form functionally graded coatings of HA/TiO₂ nanoparticles and HA-TiO₂ nanocomposite coatings with 0, 10 and 20wt.% of TiO₂ on Ti-6Al-4V substrate. The gradual addition of HA suspension into the deposition cell containing TiO₂ nanoparticles caused the functionally graded structure of HA-TiO₂ coatings. The microstructure of coatings showed the lower porosities by the addition of TiO₂ and using graded structure. The pull-off test results showed the highest bonding strength for the graded coating. The electrochemical impedance spectroscopic studies after in vitro tests, revealed that the total corrosion resistance of graded coating is higher than that of HA and HA-TiO₂ samples. The accelerated apatite formation on functionally graded coating corresponding to inductively coupled plasma spectroscopy was attributed to the higher wettability of its surface.