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

等离子体电解氧化(PEO)，又称微弧氧化(MAO)、火花阳极氧化和微等离子体氧化，是一种将铝、镁和钛等金属表面转化为厚度从几十微米到数百微米的氧化物涂层的加工技术。涂层的生长是通过局部介质击穿引起的大量短暂火花(放电)来实现的。生成的涂层具有高度的耐磨性和耐腐蚀性，并且与基材的附着力非常好。然而，直到最近，人们对这些等离子体放电的性质以及它与所产生的涂层微观结构之间的联系还知之甚少。谢菲尔德和剑桥大学最近的工作提供了关于这些放电的温度、密度、电阻率、空间分布、频率和持续时间以及这些特征对涂层微观结构的影响的新信息。拟议的项目旨在利用和扩展在这项工作中开发的技术，雇用主要负责这些进展的研究人员，并受益于南安普敦经验丰富的等离子体物理学家的投入。目标之一将是创建一个新的流程模型。这将使人们对电路、电解液成分、等离子体放电特性和涂层微观结构之间的相互作用有定量的了解。这应有助于实现提高该进程的能源效率的目标。然后，将利用这种模拟提供的更好的理解来探索使用类似PEO的工艺将小原子(如碳和硼)注入到钢等金属中的可能性，从而提高表面硬度。关于这种可能性的初步报告令人鼓舞。如果它确实被证明是可行的，那么它将提供与传统渗碳竞争的主要节能效益，后者要求部件在高温下长时间保持。这项工作将与PEO领域的两家英国中小企业合作进行，因此应该会为英国工业带来实质性和相对短期的好处。

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.