RESUMEN
To decrease energy consumption and improve the performance of micro-arc oxidation (MAO) films on 6063 Al alloy, a policy of K2TiF6 additive and electrolyte temperature control was adapted. The specific energy consumption relied on the K2TiF6 additive and more particularly on the electrolyte temperatures. Scanning electron microscopy demonstrates that electrolytes with 5 g/L K2TiF6 can effectively seal the surface pores and increase the thickness of the compact inner layer. Spectral analysis shows that the surface oxide coating consists of γ-Al2O3 phase. Following 336 h of the total immersion process, the impedance modulus of the oxidation film, prepared at 25 °C (Ti5-25), remained 1.08 × 106 Ω·cm2. Moreover, Ti5-25 has the best performance/energy-consumption ratio with a compact inner layer (2.5 ± 0.3 µm). This research found that the time of the big arc stage increased with the temperature, resulting in producing more internal defects in the film. In this work, we employ a dual-track strategy of additive and temperature providing an avenue to reduce the energy consumption of MAO on alloys.
RESUMEN
In the current investigation, micro-arc oxidation (MAO) ceramic coatings on aluminum are galvanostatically synthesized at various processing stages in an alkaline silicate system. The resultant coatings are systematically investigated in terms of the following respects: The working voltage and surface sparking evolution over the studied course of MAO are recorded by the signal acquisition system and the real-time imaging, respectively; the phase composition, the surface morphology, and the polished cross-section of the coatings are characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) assisted with an energy-dispersive X-ray spectrometer (EDS), respectively. In particular, with the help of a low-rate increase in working voltage, the evolution of the sparks, the energy consumption, and the microstructure development of aluminum in alkaline silicate electrolyte by pre-anodizing are systematically investigated. The results show that the pre-anodized film can accelerate the evolution process of MAO spark and shorten the reaction process in the early stage of MAO reaction, reducing energy consumption and improving the corrosion resistance of the MAO coating. The γ-Al2O3 phase content after pre-anodized is significantly increased in MAO coatings. In particular, the thicker the pre-anodized film (beyond 8 µm) was broken down and fragmentation thinning in the early stage of the MAO process with the presence of micro discharges. This is due to the fact that the electron transition will be released by the emission of radiative recombination and reveals obvious galvanoluminescence (GL) behavior on the surface of the pre-anodized film. Further, based on the present MAO coating microstructure, a model of coating growth after pre-anodized that evolves over time is proposed.
