Characteristics of heat-treated plasma-sprayed CaO–MgO–SiO2-based bioactive glass–ceramic coatings on Ti–6Al–4V alloy

• A novel bioactive glass–ceramic M2 was firstly plasma-sprayed onto Ti–6Al–4V alloy.
• The amount of micro-cracks in M2 coating was smaller than that of commercial HA coating.
• M2 coating on Ti–6A1–4V substrate was nearly twice the bonding strength of HA coating.
• Ti–6Al–4V/M2 coating composite had good bioactivity and cytocompatibility in vitro.

In this study, a novel CaO–MgO–SiO2-based bioactive glass–ceramic M2 (43.19% CaO–7.68% MgO–49.13% SiO2 (wt.%)) was coated onto Ti–6Al–4V substrates by atmospheric plasma spraying (APS) to evaluate its application potentials in biomedicine. The bonding strength, phase composition and morphologies of commercial plasma-sprayed hydroxyapatite (HA, Ca10(PO4)6(OH)2) coatings and M2 coatings before and after heat treatment at 650–800 °C were investigated. The M2 coatings were soaked in simulated body fluid (SBF) to evaluate their bioactivity in vitro, and the cytocompatibility in vitro was detected by osteoblast proliferation, differentiation and adhesion assays. The results indicated that heat treatment could induce recrystallization of the as-sprayed M2 coatings, and the optimum condition for heat treatment might be 800 °C for 6 h in air. Compared with commercial HA coating, the micro-cracks in the heat-treated M2 coating were much less, and the bonding strength of M2 coating to Ti–6Al–4V substrate was nearly twice as much as that of HA coating. In addition, M2 coating possessed a bone-like apatite-formation ability in SBF. The M2 coating extracts at certain concentrations could stimulate the proliferation and differentiation of osteoblasts, and cells adhered and spread well on M2 coatings, indicating good bioactivity and cytocompatibility in vitro.