Deposition behavior and characteristics of hydroxyapatite coatings on Al2O3, Ti, and Ti6Al4V formed by a chemical bath method

A simple chemical bath method was used to deposit hydroxyapatite (HA) coatings on Al2O3, Ti, and Ti6Al4V substrates at ambient pressure by heating to 65-95 °C in an aqueous solution prepared with Ca(NO3)2·4H2O, KH2PO4, KOH, and EDTA. The deposition behavior, morphology, thickness, and phase of the coatings were investigated using scanning electron microscopy and X-ray diffractometry. The bonding strength of the coatings was measured using an epoxy resin method. The HA coatings deposited on the three kinds of substrates were fairly dense and uniform and exhibited good crystallinity without any additional heat treatment. A coating thickness of 1-1.8 μm was obtained for the samples coated once. By repeating the coating process three times, the thickness could be increased to 4.5 μm on the Al2O3 substrate. The bonding strength of these coatings was 18 MPa.