Effect of hydrothermal treatment temperature on the hydroxyapatite coatings deposited by electrochemical method

Hydroxyapatite coatings on titanium alloy prepared via electrochemical method show low crystallinity and form cracks that affect implant performance. In this study, the hydrothermal treatment was applied in order to improve the properties of the hydroxyapatite coating. Ti6Al4V substrates were coated with hydroxyapatite via the electrochemical method. The samples were then hydrothermally treated under different temperatures. The effects of hydrothermal treatment temperatures on the hydroxyapatite coating composition, microstructure, crystallinity, as well as on the bonding strength between coatings and substrates, were investigated. The samples' bioactivity was measured by immersing them in a simulated body fluid. Results showed that the hydrothermal treatment healed the cracks of the hydroxyapatite coating deposited by electrochemical method. The coatings became denser with increasing hydrothermal teatment temperatures. The hydrothermal treatment temperatures had negligible effects on hydroxyapatite coating composition. At 180 °C, the hydroxyapatite coating achieved maximum crystallinity, and their bonding strength was about 23 MPa. Bioactivity experiments revealed that the hydroxyapatite coatings obtained via the electrochemical method and the hydrothermal treatment had good bioactivity. •Ti6Al4V substrates have been coated with hydroxyapatite by electrochemical method.•Hydrothermal treatment was carried out to the samples under different temperatures.•The crystallinity and the bonding strength increase with increasing temperature.•When the temperature is 180 °C, the HA has the maximum crystallinity and bonding strength.•The hydrothermal treatment can heal the cracks of the hydroxyapatite coating.