Adhesion of Hydroxyapatite Layer Prepared by Thermal Plasma Spraying to Titanium or Titanium (IV) Oxide Substrate.

Hydroxyapatite (HAp) was sprayed onto titanium substrates in argon-hydrogen thermal plasma or onto titanium (IV) oxide substrates in argon-oxygen thermal plasma. In the latter case, no adhesive strength by a tensile test could be measured because of high fragility of the titanium (IV) oxide. Comparison of the width of peeled-off layers by a scratch test suggested a higher adhesive strength of HAp layers sprayed onto titanium (IV) oxide than onto titanium substrates. It seemed that the surface oxide layer of the titanium substrate would give a positive contribution to adhesion. In both the above experiments, adhesive strength increased with the substrate temperature up to 1130°C and the maximum adhesive strength was 19.2MPa for layers sprayed onto titanium.