Adhesion of thermally sprayed hydroxyapatite-bond-coat systems measured by a novel peel test

Ti6Al4V foils, 100 microm thick, were coated with thin (10-15 microm) bond coats based on titania and zirconia, and subsequently coated with a thick (100-120 microm) hydroxyapatite layer, using atmospheric plasma spraying. Peel adhesion tests of the coating systems performed on the foils showed that titania, and mixed titania/non-stabilized zirconia bond coats improved the adhesion of the ceramic layers to the metallic substrate in a statistically significant way, while a partially CaO-stabilized zirconia bond coat led to a decrease of the peel adhesion strength when compared to hydroxyapatite coatings without a bond coat.