Breakthrough Studies on the Plasma Electrolytic Oxidation (PEO) Coating Process

点击翻译按钮获取中文摘要

Plasma Electrolytic Oxidation (PEO), also known as Micro Arc Oxidation (MAO), Spark Anodising and Microplasma Oxidation, is a processing technique in which the surfaces of metals such as Al, Mg and Ti are converted into oxide coatings, ranging from tens to hundreds of microns in thickness. Coating growth occurs via large numbers of short-lived sparks (electrical discharges), caused by local dielectric breakdown. The resultant coatings can be highly resistant to wear and corrosion, and adhere exceptionally well to the substrate. Until recently, however, the nature of these plasma discharges, and the links between this and the resultant coating microstructure, have been very poorly understood. Recent work at Sheffield and Cambridge has produced new information about the temperature, density, resistivity, spatial distribution, frequency and duration of these discharges, and also about the influence that these characteristics have on the coating microstructure. The proposed project is aimed at utilising and expanding the techniques that have been developed in this work, employing the researchers primarily responsible for these advances, and also benefitting from the input of experienced plasma physicists based in Southampton. One of the objectives will be to create a new process model. This will give quantitative insights into the interplays between electrical circuitry, electrolyte composition, plasma discharge characteristics and coating microstructure. This should assist in the aim of improving the energy efficiency of the process. The enhanced understanding provided by this modelling will then be utilised to explore the potential for using PEO-like processing to implant small atoms, such as carbon and boron, into metals such as steels, giving increased surface hardness. Preliminary reports of this possibility are encouraging. If it does prove to be viable, then it would offer major energy-saving benefits in competition with conventional carburizing, which requires components to be held at high temperatures for extended periods. The work will be carried out in collaboration with two UK SMEs in the PEO field, and should thus lead to substantial and relatively short term benefits to UK industry.