Interface in Hydroxylapatite Coated Ti6Al4V Alloys

The aim of the present study is to develop a better understanding of the interface reaction between hydroxylapatite and Ti6Al4V alloys. Hydroxylapatite coatings on Ti6Al4V, Hydroxylapatite-metallic titanium powder, hydroxylapatite-titania composites were prepared via air sintering and/or hot isostatic pressing (HIP). The reaction between components was monitored with EPMA line scanning technique, XRD, and thermal analysis. EPMA analysis on the interface between the hydroxylapatite and Ti6Al4V alloy showed interdiffusion profiles of all the hydroxylapatite and alloy elements suggesting interfacial bonding. The experiments on the composites showed no significant reaction between hydroxylapatite and metallic titanium in the vacuum environment. However, a reaction occurred between hydroxylapatite and titanium oxide, which formed CaTiO3 with a perovskite structure, Ca₃(PO₄)₂ (tri-calcium phosphate; whitlockite) and water. Presence of air in the sintering environment promoted this reaction.