Effect of Alkali and Heat Treatment on Biomimetic HA Coating on Ti6Al4V

In this study, time of calcium phosphate formation on Ti6Al4V alloy with or without alkali and heat treatments was investigated. Specimens were soaked in 0, 5, 10 M solutions of NaOH at temperatures of 60 or 80 °C for 24, 72 h. Their surfaces were characterized using scanning electron microscopy and thin film X-ray diffraction. It was found that optimum condition is 72h soaking in 5 M NaOH in 80 °C. Specimens treated under these optimum conditions were subsequently heat-treated at 500, 600, and 700 °C for 1h in order to consolidate the sodium titanate hydrogel layer. With heat treatment at 600 °C for 1h and then soaking in simulated body fluid (SBF), apatite formed within 3 days. But there were no signs of apatite formation in control samples (without alkali and heat treatment) up to 7 days soaking in SBF. So, it was concluded that alkali-heat treatment is an effective way for accelerating apatite formation and the optimum condition is 72 h soaking in 5 M NaOH solution at 80°C and then heat treatment at 600 °C resulted for 1 h.