Pressure-controlled Micro-arc Treatment on Aluminum

Micro-arc treatment to form ceramic layer relies on the local arc events occurring upon the specimen surface. In spite of such a well-developed atmospheric process for a variety of applications, it would be interesting to know that how the working pressure affect the treated layers, and thus their microstructure and properties. In this study, the micro-arc treatment on metal aluminum was carried out in a home-made chamber which provides pressure-control ranging from a working pressure below atmospheric pressure to a pressure higher than that. The obtained layers were analyzed and observed. The surface hardness of the obtained layers was examined. Experimental results show that the anodic micro-arc events happened to the specimen, regardless of the working pressure employed, indicating the anodic oxidation of aluminum through the reaction with water instead of oxygen. Crystal structure, morphology and film thickness of the obtained layer can be affected by the working pressure, as a result to affect surface hardness. Details of the working pressure influence to the microstructure and surface hardness are discussed.