Glass-based coatings for titanium implant alloys

Glass coatings on Ti6Al4V were prepared using a simple enameling technique. The composition of the glasses was tailored to match the thermal expansion of Ti6Al4V. By controlling the firing atmosphere, time, and temperature, it was possible to control the reactivity between the glass and the alloy and to fabricate coatings (25-150 micron thick) with excellent adhesion to the substrate. The optimum firing temperatures ranged between 800 and 840 degrees C at times up to 1 min in air or 15 min in N2. The same basic technique was used to prepare multilayered coatings with graded composition or with hydroxyapatite (HA) particles embedded in the outer layer. Some of these coatings presented excellent adhesion to the substrate and were able to form HA during in vitro tests in simulated body fluid.