Mechanical and chemical properties of Baghdadite coatings manufactured by atmospheric plasma spraying

Baghdadite (Ca3ZrSi2O9) (BAG) is a calcium silicate (Ca-Si) based ceramic that demonstrates osteostimulatory function, biocompability and chemical stability. This work studies atmospheric plasma sprayed (APS) BAG and APS hydroxyapatite (HAp) coatings by evaluating their phase compositions, chemical properties, coating microstructure and mechanical properties. BAG coatings presents well-melted spherical splats without splashes or fragmentations, while HAp coatings reveal irregular splat shapes that exhibit large splashes and fragmentations. The surface of BAG coatings contains uniform features and less variants than the surface of HAp coatings. The BAG coatings present phases of BAG, calcium silicate and zirconium dioxide, while phases of HAp, tricalcium phosphate and calcium oxide can be found in the HAp coating. The BAG coatings show a more uniform microstructure and greater mechanical properties than the HAp coatings, although BAG coatings show lower level of crystallinity compared with the HAp coatings. Microhardness values of BAG coatings are significantly higher than those of HAp coatings. The distribution of mechanical properties including nanohardness and elastic moduli; which are more consistent and less variable in the BAG coating than those of the HAp coating. The presence of zirconium in BAG coatings increased the microhardness, as well as the hardness and elastic moduli derived from nanoindentation measurements, when contrasted with the properties of HAp coatings. The in vitro result indicated that the BAG coating can promote the healthy development of osteoblast-like MG-63.