Structural-Morphological and Adhesive Properties of Calcium-Phosphate Coatings Formed on a Magnesium Alloy by Microarc Oxidation in an Electrolyte Containing Disperse Particles

Common patterns of calcium-phosphate coating formation by the method of micro-arc oxidation (MAO) in the anodic potentiostatic mode on the Mg0.8Ca alloy surface in an electrolyte containing disperse particles of beta tricalcium phosphate (β-TCP) are studied. As a result of plasma-chemical reactions of interaction between the components of the electrolyte and the magnesium substrate, with the MAO voltage varied in the range of 350–500 V, a porous ceramic-like coating with β-TCP particles is formed on the surface. The influence of the structural-morphological properties of the coatings, formed under different voltages, on their adhesion properties is determined. The highest adhesive strength at a value of the ultimate load of 19 N is exhibited by the coatings with a thickness of 80 μm, a roughness of 8 μm, a surface porosity of 23%, and an average pore size of 5.9 μm, deposited at the MAO voltage of 500 V. The fracture of these coatings is completed at the interface between the coating and the intermediate oxide layer between the coating and the magnesium substrate.