Characterization of immersed hydroxyapatite-bioactive glass coatings in Hank’s solution

Monolithic HA and hydroxyapatite-bioactive glass (HA–BG) coatings have been plasma-sprayed on Ti–6A1–4V substrate using sinter-granulated HA and HA–BG powders. The immersion behavior of these coatings in Hank’s physiological solution was investigated. The results showed that sinter-granulated monolithic HA powder was irregularly-shaped and appeared quite dense. When 5 wt.% or more BG was added in HA, the powder became rough and porous. X-ray diffraction patterns showed that the presence of BG enhanced the decomposition of HA structure during fabrication of the powder. The plasma spray process itself also enhanced the decomposition of apatite. Surface morphology of the present HA–BG coatings was not much different from that of monolithic HA coating, that comprised patches of smooth and shiny glassy film and irregularly-shaped particles on its surface. Reasonably high bond strengths were obtained from all as-plasma-sprayed coatings. When immersed in Hank’s solution, these bond strengths largely declined.