Nitrogen inducing effect on preparation of AlON-Al2O3 coatings on Al6061 alloy by electrolytic plasma processing

In this work, AlON-Al2O3 coatings were prepared on Al6061 alloy 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, 0.3-0.9 g/l NH4NO3 and 0.3-0.7 g/l NaNO3 as nitrogen supply agents. The nitrogen inducing effects were studied by a combined composition and structure analysis of the coating layer carried out by X-ray diffractometer (XRD), scanning electron microscopy (SEM) for the specimens EPP treated at room temperature for 15 min under a hybrid voltage of 260 V DC plus 200 V AC (50 Hz) power supplies. In addition, microhardness values were measured to correlate the evolution of microstructure and resulting mechanical properties. The results demonstrate that NaNO3 is a good nitrogen inducing agent to produce high quality AlON-Al2O3 coatings.