MICROSTRUCTURAL CHARACTERIZATION OF HYDROXYAPATITE COATING ON TITANIUM

The microstructure of hydroxyapatite plasma sprayed onto titanium alloy has been studied by using transmission electron microscopy. It has been shown that while substantial portions of the coating are crystalline hydroxyapatite, regions of amorphous calcium phosphate with Ca/P ratios of 0.6-1.0 are also present, both in the coatings and at the metal-ceramic interface. The microstructures observed have also been found to be consistent with devitrification of the amorphous calcium phosphates producing regions of very fine grained hydroxyapatite. A calcium titanate phase has also been detected at the metal-ceramic interface produced by the chemical reaction of hydroxyapatite to titanium.