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

Abstract

The micro-arc oxidation method has been used to obtain bioactive calcium-phosphate coatings on titanium surface. 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 microarc 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 μm, 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(H2PO4)2(H2O) and CaPO3(OH) in the coatings.