PATTERNS OF FORMATION OF PEO-COATINGS ON ALUMINUM ALLOYS

In the practical application of microarc oxidation technology, the most important technological factors are obtaining a coating of a given thickness with the required microhardness. The multifactorial nature of the process complicates this task. (Research purpose) The research purpose is searching for empirical dependencies of thickness and microhardness on the parameters of the source and the composition of the electrolyte for the anode-cathode process. (Materials and methods) Were used the formulas of the regression equation with the effect of the interaction of influencing factors. The values of the factors were taken from literary sources and the results of their own experiments. The thickness and microhardness of the coating were measured on micro-grinders using a KMT-1 microhardness meter and an Olympus GX51 metallurgical microscope. (Results and discussion) The analysis of the main factors of the process of obtaining ceramic coatings affecting the microhardness and thickness of the coating was performed. It was found that the main indicators are the ratio of the anode and cathode component and the current density of the power source, the concentration of components and additives in the electrolyte and the duration of oxidation. (Conclusions) Regression models of mathematical prediction of coating properties were obtained depending on the application conditions and the most commonly used aluminum alloys. For copper-containing alloys, the current density is the determining factor affecting the coating growth rate and microhardness. The recommended current density is 15-20 amper per square decimeter. From the analysis of the obtained models, it follows that for silicon-containing alloys, the percentage of caustic potassium and sodium metasilicate have a significant effect on the growth rate and microhardness. It is recommended to use a solution containing caustic potassium 2 grams per liter and sodium silicate 8-10 grams per liter. The introduction of nano-additives in the form of artificial diamond in the amount of 1-2 grams per liter into the electrolyte leads to an increase in the thickness of the main technological layer by 46 percent and an increase in microhardness by 25-30 percent with respect to all the alloys considered.