Alkali-Heat Treatment of Ti-6Al-4V to Hydroxyapatite Coating Using Electrophoretic Method

Abstract

The deposition of hydroxyapatite has been applied to enhance the bioactivity of Ti-6Al-4V as implant materials. However, the hydroxyapatite has poor adhesion strength to a substrate which can lead to coating delamination. In this study, we combine the alkali-heat treatment of Ti-6Al-4V and the electrophoretic coating process of the hydroxyapatite to obtain the strong mechanical interlocking. The Ti-6Al-4V implants were etched in Kroll solution before the alkali-treatment was performed using 5M and 10M NaOH at 24, 48 and 72 hours and thermally stabilized at 600°C and 800°C for 1 hour using a stepwise heating rate of 5°C per min. The electrophoretic deposition process conducted at a constant cell voltage of 20 V for 10 min at room temperature and then sintered in a vacuum furnace at 800°C. The result shows that the feather-like structure on Ti-6Al-4V surface was created by incorporating sodium ions onto the Ti-6Al-4V surface during alkali-treatment using NaOH 5M for 48h and stabilized using heat treatment at 600°C where the hydroxyapatite filled the interspaces to become integrated with the feather-like structure so that the osseointegration can occur as the bioactivity increased.