Structural, morphological and adhesive properties of calcium phosphate coatings formed on magnesium alloy by micro-arc oxidation method in electrolyte containing dispersed particles

The regularities of the calcium phosphate (CaP) coatings formation by the method of micro-arc oxidation (MAO), in the anodic potentiostatic mode, on the Mg0.8Ca alloy have been studied. The coatings deposition was carried out in the electrolyte containing dispersed β-tricalcium phosphate (β-TCP) particles. The porous ceramic-like layer was formed in the range of the process voltage of 350-500 V as a result of plasma-chemical reactions during the interaction of electrolyte components with the magnesium substrate. In this case, the β-TCP particles were deposited on the coatings surface from the electrolyte. The effect of the structural and morphological properties of the coatings formed at different voltages on their adhesion properties has been revealed. The coating synthesized at the voltage of 500 V demonstrated the highest adhesion strength at the critical breaking load of 19 N. This coating had the thickness of 80 μm, the roughness of 8 μm, the surface porosity of 23% and the average pore size of 5.9 μm. Destruction of this coating finished at the interface between the coating and the intermediate oxide layer located on the border of the coating and the magnesium substrate.