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Influence of electrical parameters of the micro-arc oxidation mode on the structure and properties of coatings
(Institute for Single Crystals, 2022) Subbotina, V.; Bilozerov, V.; Subbotin, O.; Barmin, O.; Hryhorieva, S.; Pysarska, N.
The influence of different power sources of the micro-arc oxidation process on the peculiarities of structure formation and properties of coatings on aluminum alloy AB formed in alkali-silicate electrolyte in the anode-cathode mode is investigated. It is shown that the pulse technology and the anode-cathode mode make it possible to form coatings containing mainly oxides of the α-Al₂O₃ type (corundum) with a high growth rate. It has been established that with a small thickness of the oxide layer, the rate of heat removal both to the metal and to the electrolyte is high; this fact promotes the formation of alumina in the form of the γ-Al₂O₃ phase. The energy concentration in the thick oxidizing layer causes the formation of high-temperature modification of α-Al₂O₃. It is shown that the mechanism of α-Al₂O₃ formation is determined by two factors: the energy difference in the formation of γ-Al₂O₃ and α-Al₂O₃ phases, and the polymorphic high-temperature transformation of γ-Al₂O₃→α-Al₂O₃ in the high-temperature region of the arc discharge.