The study of oxide films on the surface of a piston of aluminum alloy after micro-arc oxidation

Abstract

One of the promising methods of surface hardening of piston aluminum alloys – micro-arc oxidation-is considered in the paper. This type of coating, formed under the influence of micro discharge in the electrolyte solution, is fundamentally different from the base metal. A qualitative analysis of the piston alloy on the energy dispersion x-ray fluorescence spectrometer was carried out for a more accurate assignment of the oxidation parameters, which allowed the most accurate determination of the chemical composition of the alloy. Micro-arc oxidation of the pistons was carried out at the experimental laboratory facility, which allowed to regulate the total density of the ion current II and the quantitative ratio of cathode and anode currents IK/IA in a wide range, which favorably affected the quality of the oxide layers. The mechanism of formation of crystalline inclusions and high-temperature structures depending on the ion current density in time is also described. The conditions of formation of oxide films on the surface of piston alloys based on the physical-geometric Keller model are described and their characteristic features are revealed. The technique of investigation of microstructures of thin films is considered, its characteristic features are described. The obtained microstructures of piston aluminum alloys after micro-arc oxidation are presented. Mechanisms of formation of oxide layers are considered taking into account the influence of alloying elements of piston aluminum alloys. Microphotographs of individual porous cells obtained with the help of an electronic scanning microscope are also shown and analyzed. The basic properties that should have a piston of aluminum alloys: heat resistance, corrosion resistance and abrasive wear. Methods of their research are described. The complex analysis of the received results is carried out. The conclusion about the prospects of these oxide coatings is made.