Effect of electric mode of micro-arc oxidation on structural and phase state of calcium-phosphate coating

The micro-arc oxidation method has been used to obtain calcium-phosphate coatings on titanium surface, expected to have bioactive properties. The effect of the pulse current duty cycle and voltage of micro-arc oxidation on the morphology, elemental and phase composition of the coating has been studied. Decrease in the pulse duty cycle during micro-arc oxidation results in the formation of flake, spheroidal and lamellar structures. It has been shown that the Ca/P ratio and surface roughness of the coating increases regardless of the pulse duty cycle with increase of applied voltage. Depending on the application mode, the Ca/P ratio and the roughness of calcium phosphate coatings ranged from 0.44 to 0.67 and from 4.2 to 6.8 μ m, respectively. It was found that change of the pulse current duty cycle and increase of the voltage up to 600 V results in the formation of the main crystalline phases Ca(H _2 PO _4 ) _2 (H _2 O) and CaPO _3 (OH) in the coatings.