| 초록 |
Plasma electrolytic oxidation (PEO), or microarc oxidation (MAO), is an electro chemical and physical surface treatment process for generating oxide coatings on metals. It is used to grow thick and large-crystalline ceramic oxide coatings on metals such as aluminum, magnesium and titanium[1]. Because they can present high hardness and continuous barriers, these coatings can offer good protection against abrasion, corrosion and heat as well as electrical insulation. In the present work, 6XXX series aluminum alloy is choosed as the matrix material for its high performance amplitude among these metals. As the electrolyte composition, voltage, current, frequency, reaction time are the main parameters of influence with the final coating property[2]. This study try to figure out the electrolyte with best cost-performance. The experimental electrolyte composition includes: 0.5-2 g/L NaOH as the electrolytic conductive agent, 2-20 g/L Na2SiO3 as the coating formative agent, 0.5-2 g/L NaCl as a special functional agent[3]. A combined composition and structure analysis of surface and cross section layer was carried out by XRD, OM, SEM&EDS for the specimens PEO-treated at different time intervals with 200DC plus 200AC 50Hz power supply. In addition, micro hardness on the surface and cross section layer were measured to correlate the evolution of microstructure and resulting mechanical properties. In different electrolytes, the surface morphologies oberved by SEM have different appearances, and also with the different mechanical properties exiting. And as the reaction time increases, the ceramic coating thickness and micro hardness of section layer also have corresponding increase. More detailed investigation is required to provide full optimisation of PEO process and a deeper insight into the composition-structure-property relationships for the coatings produced, in oder to acquire the final cost-performance electrolyte composition. |
