Influence of microarc machining on resizing of aluminum parts
Authors: Subbotin Olekcandr , Belozerov Valerii , Subbotinа Valeria 
Published: September 2022

Problem. The change of the sizes of the processed samples (aluminum alloys) after oxidation in alkaline-silicate electrolyte at the anode-cathode mode is studied in the work. The two-layer structure of aluminum alloys after MAO processing is shown. The change in the size of the parts is determined by the phase composition of the coating. Goal. The goal is study of the changes in the size of the processed samples (aluminum alloys) after oxidation in alkaline-silicate electrolyte at the anode-cathode mode. The change of the sizes of the processed samples (aluminum alloys) after oxidation in alkaline-silicate electrolyte at the anode-cathode mode is studied in the work. Methodology. X-ray structural analysis (Dron - 3) in radiation Кα-Cu, microhardness measurement (PMT-3) with the load of 100 gr., measurement of coating thickness (vortex thickness gauge BT - 10NTs).  Results. It is shown that in the case of predominant α- Al2O3 formation the δ / B ratio is 1.28, in the case of γ-Al2O3 formation, the δ / B ratio is 1.55 and in the case of mullite formation (3Al2O3 • 2SiO2) - 2.23. The calculation showed that the level of change in the size of the sample after MАO significantly depends on the phase composition of the coating. Experimental testing on different alloys and different electrolytes confirmed the different degree of change in size depending on the phase composition of the coating, which is determined by the modes of MAO and the composition of the electrolyte. Thus, the experimental value for alloy D16 subjected to MАO in different modes varies from 1.0 to 2.0; for B96 metal - 1.15-2.76; for AMg6 metal - 1.46-2.55. The results presented above relate to the total thickness of the formed coating. Given the two-layer structure of the coating and the fact that the thickness of the loose layer to be removed is 15 - 50% of the total thickness, the change in the size of the part after the final finishing of the friction surface should be insignificant. It has been experimentally established that from alloys D16, B96, AMg6 at optimal modes of MAO (thickness of wear-resistant coating 100 - 150 μm) the increase in the size of the part to the side is 5 - 10 μm. As for cast alloys (for example, Al9), the structure of the coating which contains a significant amount of mullite, the increase in the size of the part of such alloy after MАO and refining, more (compared to deformed alloys) and is 20 - 30 microns Al2O3. Originality. The calculation and research showed that the level of change in the size of the sample after MDO significantly depends on the phase composition of the coating itself. Considering the two-layer structure of the coating and the fact that the thickness of the loose layer to be removed is 15 - 50% of the total thickness, the change in the dimensions of the part after the final proofing of the surface should be insignificant. Practical value. Changes in the dimensions of the part must be taken into account when processing parts with small tolerances or eliminated by additional finishing by partially removing the main wear-resistant layer.