Adhesion improvement and in vitro characterisation of 45S5 bioactive glass coatings obtained by atmospheric plasma spraying

Abstract

Plasma sprayed bioactive glass coatings were studied using crushed 45S5 bioactive glass powder. It is widely accepted that plasma sprayed coating microstructure is highly affected by the characteristics of the powder and the parameters set on the spraying process. Once the coating deposition was optimized, two strategies were carried out to analyse their effect on the coating adhesion: cooling with carbon dioxide while spraying and a post heat treatment to the as-sprayed coatings. Scanning electron microscopy and X-ray diffraction were used for analyse the obtained coatings. Additionally, coating adhesion to the substrate and degradation of the coatings in Tris buffer solution were evaluated for the different samples studied. Coatings have been tested in vitro to evaluate their response by immersion in simulated body fluid, Hank's Balanced Salt Solution. The results show an increase in the adhesion strength for the heat treated samples due to the stress relaxation achieved above glass transition temperature. Moreover, in the bioactivity test an apatite layer at the coatings surface was produced for all the strategies studied.