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-6A1-4V substrate using the spray-and-sinter method and the coating produced was evaluated using various techniques. Commercially available spherical HA (SHA) and alpha -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-6A1-4V plates at room temperature using an airbrush under controlled pressure. The FGC on Ti-6A1-4V was sintered at 900 degreesC. No HA decomposition was encountered with this coating technique and the FGC retained functional soups for its bioactivity. This coating is both bioactive and biodegradable as it contains HA and TCP.