Bonding strength investigation of plasma-sprayed HA coatings on alumina substrate with porcelain intermediate layer

Hydroxyapatite (HA) has recently been used as a bone substitute in orthopedic and dental surgery applications, owing to its excellent biocompatibility. However, the poor mechanical properties of HA limit the material's application in the loading condition. In this study, HA was coated onto the surface of alumina substrate, with a view to overcome the poor mechanical properties of HA and the biocompatibility of alumina. Improvement of the bonding strength of HA coatings to alumina substrate was attempted by adding a bond coat of porcelain via plasma-spraying and by post-heat-treatment. HA–50 wt% porcelain and pure porcelain were used to manufacture two kinds of bond coat before HA coating, and then all the specimens were heat-treated at 750, 800, 850, and 900 °C for 0.5 h. The results shows that the bond strength between HA coating and Al2O3 substrate could be improved by employing the porcelain as the bond coat after the heat-treatment. The strengthening mechanisms of the two systems are discussed.