Characteristic of AlON–Al2O3 coatings on Al6061 alloy by electrolytic plasma processing in aluminate and nitride electrolytes

In this work, 6061 series aluminum alloy is used as the matrix material for its wide application in engineering to make AlON coating layers by the electrolytic plasma processing (EPP) method. The experimental electrolytes include: 10 g/L NaAlO2 as alumina formative agent, 2 g/L NaOH as the electrolytic conductive agent, 0.4 g/L NaNO3 as a nitride supply agent. A combined composition and structure analysis of the coating layer was carried out by X-ray diffractometer (XRD) and scanning electron microscopy (SEM) for the specimens EPP-treated at 25 °C in 5 to 30 min under a hybrid voltage of 260 V DC plus AC 50 Hz power supplies (200 V). In addition, microhardness values were measured to correlate the evolution of microstructure and resulting mechanical properties. A composite of AlON–Al2O3 coating was formed as a result of a reactive process between Al in the alloy itself and O–N supplied by the electrolyte, which presents high hardness and anti-abrasion behaviors.