Effects of anodic oxidation and hydrothermal treatment on surface characteristics and biocompatibility of Ti–30Nb–1Fe–1Hf alloy

Anodic oxidation followed by hydrothermal treatment has been widely applied for surface modification of titanium alloys to precipitate a crystalline hydroxyapatite (HA) layer in order to achieve improved osteoconduction. A majority of the studies in the literature imposed relatively high powers to enhance Ca and P in the anodic oxide film (AOF). However, high powers have been found to cause deterioration of the adhesive strength in one of the authorʹs previous study. In this study, a new electrolyte comprising calcium acetate monohydrate (CA), β-glycerophosphate disodium pentahydrate (β-GP) and HA powder was developed, and the Ti–30Nb–1Fe–1Hf alloy was anodized in this HA-containing electrolyte to a relatively low voltage. Results show that the AOF anodized in the HA-containing electrolyte exhibits a better HA forming ability during hydrothermal treatment, attributing to the presence of HA powder in the electrolyte that effectively enhances both the Ca content and Ca/P ratio in the AOF. On the other hand, the adhesive strength was little affected due to the decrease in size of the craters residing in the AOF. With respect to the biological responses, not much difference in biocompatibility of the treated and untreated Ti–Nb surfaces was obtained. However, the anodized and hydrothermally treated surface promotes the attachment of cells.