Effect of feedstock and plasma gun on the microstructure and bioactivity of plasma sprayed bioactive glass coatings

Plasma-sprayed 4555 bioactive glass coatings were manufactured using two types of powder feedstocks (commercial and lab-made 4555 glass) and two plasma torches (single and triple cathode) to analyse their influence on the microstructure and bioactivity of the coatings. Besides, the volatilisation of glass oxides such as Na2O and P2O5 during the deposition was studied. All coatings were microstructurally characterised by scanning electron microscopy, X-ray diffraction and X-ray dispersive energy analysis. Moreover, the bioactivity of the sprayed coatings was studied by immersing the coatings in Simulated Body Fluid until 14 days. The coatings obtained using the triple cathode torch showed similar thickness, less total porosity and greater microstructural homogeneity than the coating deposited with the single cathode torch. X-ray dispersive energy analysis revealed lower amounts of sodium and phosphorus at the surrounding of the lamellae, due to its volatilisation during the formation of the coatings. The volatilisation of these elements varied depending on the type of feedstock and plasma jet enthalpy. Concerning the bioactivity of the coatings, all of them have developed a hydmxycarbonate apatite layer on their surface.