Microwave-hydrothermal method post-treatment of sprayed Ca-P coating

Supersonic atmospheric plasma sprayed (SAPS) calcium phosphate (Ca-P) coating is post-processed by microwave-hydrothermal (MH) method for the reduction of the surface defects in our previous work. During the MH process, ethylenediaminetetraacetic disodium salt (Na₂EDTA) as complexing agent is added during the MH reaction, while controlling the pH values, to achieve the purpose of grain refinement and decrease the surface defects, and enhance the corrosion resistance of the sprayed Ca-P coating. Afterward, surface morphologies, element and phase composition of the coating, chemical groups, surface roughness, porosity, bioactivity and corrosion resistance are all studied. The results show that the addition of Na₂EDTA and the adjustment of pH value during MH treatment do have a positive effect on grain refinement, and improvement the bioactivity and corrosion resistance of the sprayed Ca-P coating. Expressly, their corresponding corrosion potential are − 0.1105 ± 0.0025, − 0.1072 ± 0.0012 and − 0.3021 ± 0.0021 V according to the corrosion current density 2.19 × 10⁻⁶, 1.89 × 10⁻⁵and 1.71 × 10⁻⁵ A/cm², respectively.