Effect of External Ultrasound Action During Micro-Arc Oxidation on the Regularity of Calcium Phosphate Coating Growth

Regularities in thickness and roughness growth of calcium phosphate coating during the micro-arc oxidation process under external ultrasound field are studied. The relationship of the electrophysical parameters of the ultrasound assisted microarc oxidation (current density and time) to the physicochemical properties of the coatings (thickness, roughness, thickness growth rate, and roughness growth rate) is established. It is found that the increase in the thickness and roughness of the coatings with the deposition time occurs according to the logarithmic law and that the decrease in the current density and the growth rate of the coating thickness and roughness follow the hyperbolic law. It is shown that the coatings deposited under external ultrasound have a more intensive increase in the thickness and roughness with the deposition time, compared to the control micro-arc oxidation coating. This leads to a more intensive decrease in the coating thickness growth rate during micro-arc oxidation processing under the applied ultrasound, while the change in the coating roughness growth rate are independent of such external factor as the ultrasound field.