Hydroxyapatite coating on Ti6Al4V alloy using a sol–gel derived precursor

A simple rapid-heating method was successfully developed for calcium phosphate coatings on Ti6Al4V substrates deposited by using a sol–gel derived precursor. After five repetitions of coating procedures and heat treatment at 600 °C, the formation of hydroxyapatite (HA) has been confirmed by X-ray diffractometry (XRD) analyses and the substrate material was found to be slightly oxidized. The residual organics, as revealed by X-ray photoelectron spectroscopy (XPS) spectra of a coating calcined at 400 °C, might retard the formation of calcium phosphate phase, thus only small amount of calcium phosphate phase is present. After calcining at 600 °C, calcium phosphate phase is the only one identifiable by XPS spectra. The adhesive strength of the five-coating layer on the substrate is around 60 MPa. The surface morphology of the thick HA film, calcined at 400 °C and then consolidated at 600 °C, displays porous structure arisen from rapid-heating of the bulk precursor.