Abstract
Silicon is an important element in the process of plasma electrolytic oxidation (PEO) coating formation on aluminium alloys. In the current investigation, the role of different Si sources, including treatment with silicate-based electrolyte (Na2SiO3), application of silicon-containing particles for phosphate-based electrolyte (SiO2 and Si3N4) or substrate material (Al11Si alloy), on the formation of PEO coatings and respective Si incorporation was studied. The participation of silicon from various silicon sources in the process of coatings’ formation depends on the achieved processing voltage and efficient temperature of discharges. Overall, reaching of the final voltage over 480 V was significant due to the importance of high local temperatures during the PEO processing for the formation of silicon-containing phases on different substrates (AA2024 and Al11Si alloys). However, the same final voltage (480 V) was not sufficient for the formation of silicate phases when micro-sized SiO2 and nano-sized Si3N4 particles were added to phosphate-based electrolyte due to their larger size or high chemical stability. The most efficient way of silica incorporation into the coatings was the strategy based on the coating formation from silicate electrolyte. In that case, a relatively thick (35 ± 5.5 µm) and uniform coating was formed on the surface of AA2024.
DOI Link to Publication