Production and evaluation of hydroxyapatite-tricalcium phosphate functionally graded coating

A functionally graded coating (FGC) consisting of hydroxyapatite (HA) and tricalcium phosphate (TCP) was made on Ti-6Al-4V substrate using the spray-and-sinter method and the coating produced was evaluated using various techniques. Commercially available spherical HA (SHA) and α-TCP were used to make HA/TCP composite powders. The composite powders were produced by mixing appropriate amounts of HA (e.g. 50wt%) and TCP (e.g. 50wt%) in a laboratory planetary mill. The FGC was subsequently manufactured by spraying composite powders of different compositions layer by layer onto Ti-6Al-4V plates at room temperature using an airbrush under controlled pressure. The FGC on Ti-6Al-4V was sintered at 900°C. No HA decomposition was encountered with this coating technique and the FGC retained functional groups for its bioactivity. This coating is both bioactive and biodegradable as it contains HA and TCP.