Hydroxyapatite dispersed glass coatings on Co-Cr implant alloys

Hydroxyapatite dispersed glass coatings on Vitallium®, a cobalt-chromium alloy were prepared using a simple enameling technique. The composition of the bioinert glasses in the SiO ₂-B ₂O ₃-Na ₂O-K ₂O-MgO-Al ₂O ₃-ZrO ₂-TiO ₂ system has been tailored to match the thermal expansion of the alloys. The optimum glass composition and firing conditions (temperature and time) needed to fabricate homogeneous coatings with good adhesion to the alloy were determined. The final coating thickness ranged between 40 to 60 μm. Coatings fired under the optimum conditions do not delaminate during indentation tests of adhesion. Excellent adhesion to the alloy has been achieved through the formation of 200 nm thick interfacial layers (CrO _x. X-ray diffraction patterns for the hydroxyapatite dispersed on the glass surface showed a strong preferred orientation of the (0 0 2) plane when immersed in a simulated body fluid (SBF).