Formation of Coatings on Details from Valve Metals Alloys by Micro-Arc Oxidation in Internal Cavities of Counter Electrodes

It is shown that micro-arc oxidation (MAO), implemented according to traditional schemes in electrolytic baths with mechanical and pneumatic mixers, does not provide the formation of uniform ceramic coatings on the surfaces of holes, grooves and slots in the details from the alloys of the metals of valve group, and is characterized by a significant cost and relatively low safety. Fundamental possibility of MAO realization in the inner cavities of the special counter electrodes by passing solutions of electrolytes through them is installed. The calculated and experimental researches of MAO, applied to the processing of ball details from aluminum and titanium alloys, are conducted. The most rational design parameters of counter electrodes, as well as the rational parameters of the flow of electrolyte solutions in the clearances between the surfaces of details and counter electrodes are revealed. Innovative schemes for MAO of spherical details are developed. By measuring the thickness and hardness of the formed coatings it is proved that MAO, in the internal cavities of the counter electrodes, provides for the formation of more uniform ceramic coatings on the details from alloys of valve metals, in comparison with the traditional MAO in electrolytic baths with pneumatic and mechanical mixers.