Bioactive Glass Coatings Deposited by High-Velocity Suspension Flame Spraying (HVSFS)

Bioactive glasses, which are capable of proving excellent osteo-integration by eliciting a series of complex interactions with body fluids and living tissues, are already being used for small bulk orthopaedic prostheses and could be an improved alternative to hydroxyapatite for the production of bioactive coatings on load-bearing metallic prosthetic implants (like femoral and hip replacements, knee replacements, etc…) This study reports the first attempt at employing the innovative High-Velocity Suspension Flame Spraying (HVSFS) technique in order to deposit bioactive glass coatings. Fine (micrometric) glass particles having a composition similar to that of the A-W bioactive glass, containing about 13 wt.% P₂O₅ and 48 wt.% CaO, were dispersed into a 50% water + 50% isopropanol solvent mixture and the resulting suspension (containing 20 wt.% glass powder) was thermally sprayed onto Ti plates. Each torch pass produces a dense coating layer, featuring strong cohesion between lamellae thanks to viscous flow sintering along the interlamellar boundary. However, some porosity exists between different layers deposited during successive torch passes. In-vitro bioactivity tests indicate that the coatings interact remarkably with the simulated body fluid (SBF), developing a thick silica-rich layer containing hydroxyapatite crystals.