Chemical and electrical interaction mechanisms during the plasma electrolytic (PEO) mixed oxide formation on magnesium

镁上等离子电解（PEO）混合氧化物形成过程中的化学和电相互作用机制

• 批准号: 421508739
• 负责人: Professor Dr.-Ing. Thomas Lampke
• 金额: --
• 依托单位: Professur Werkstoff- und Oberflächentechnik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/421508739?language=en
• 关键词: Chemical; electrical; interaction; mechanisms; during

Magnesium is the lightest metallic engineering material and therefore offers an enormous potential to save weight in mobile systems. Beyond that, magnesium is easy to recycle. Excellent casting process properties and a good damping capacity towards electromagnetic and mechanical oscillations predestine magnesium materials for the construction of machine casings as well as framework and encasements for sensible sensory, optical and entertainment electronic devices. Despite the positive processing and application properties listed here, the application spectrum of magnesium alloys is currently limited due to their low resistance towards corrosive and tribological stress. Plasma electrolytic oxidation is a promising and environmentally friendly surface treatment process to encounter these technical challenges. An already successfully finished DFG-project was concerned with the substrate/electrolyte interaction before and during the discharge initiation, as well as the aimed insertion of electrolyte components into the generated PEOcoating. It was shown that by employing highly concentrated electrolytes, very hard and chemically resistant mixed oxide (chemical compositions dominated by electrolyte components rather than substrate components) coatings are producible, which hardness exceed that of MgO layers significantly. However, due to their morphology being afflicted with local defects, such coatings will negatively affect the resulting corrosion- and wear resistance. This reveals further research needs. A characterisation of the complex coat-forming processes as well as the interactions of chemical and electrical process parameters during the plasma electrolyte coating procedure is only possible by empirical means, according to the state of the art and in lack of a consistent process model. Therefore, the proposed project is aiming towards the research of action mechanisms of interacting chemical and electrical processes during the plasma electrolytic oxidation of magnesium under formation of mixed oxides. To reach this goal, the process needs to be characterised and understood in detail. For that, the charge throughput of the pulses necessary for coating formation are to be broken down into electro- and plasma-chemical parts, and specific process stages like the coat-healing Softsparking and cathodic discharges need to be systematically recorded. On this basis, hybrid pulse patterns adjusted to the individual process stages will be developed. The data foundation generated during the project will subsequently be used to create a model concept which describes the underlying mechanisms. Based on the obtained conclusions and using environmentally friendly electrolytes, adherent and low-defect mixed oxide coatings are to be generated on magnesium substrates and to be qualified for corrosively and tribologically demanding applications.

镁是最轻的金属工程材料，因此具有减轻移动系统重量的巨大潜力。除此之外，镁很容易回收。优异的铸造工艺性能以及对电磁和机械振荡的良好阻尼能力注定了镁材料可用于制造机器外壳以及敏感感官、光学和娱乐电子设备的框架和外壳。尽管这里列出了积极的加工和应用特性，但镁合金的应用范围目前受到限制，因为它们对腐蚀和摩擦应力的抵抗力较低。等离子体电解氧化是应对这些技术挑战的一种有前途且环保的表面处理工艺。一个已经成功完成的 DFG 项目涉及放电启动之前和期间的基材/电解质相互作用，以及将电解质成分插入到生成的 PEO 涂层中。结果表明，通过采用高浓度电解质，可以生产非常坚硬且耐化学腐蚀的混合氧化物（化学成分主要是电解质成分而不是基材成分）涂层，其硬度显着超过MgO层。然而，由于其形态受到局部缺陷的影响，此类涂层将对最终的耐腐蚀性和耐磨性产生负面影响。这揭示了进一步的研究需求。根据现有技术并且缺乏一致的工艺模型，只能通过经验手段来表征复杂涂层形成过程以及等离子体电解质涂覆过程中化学和电工艺参数的相互作用。因此，该项目旨在研究在混合氧化物形成下镁的等离子体电解氧化过程中相互作用的化学和电过程的作用机制。为了实现这一目标，需要详细描述和理解该过程。为此，涂层形成所需的脉冲的电荷吞吐量将被分解为电化学和等离子体化学部分，并且需要系统地记录涂层修复软火花和阴极放电等特定工艺阶段。在此基础上，将开发适应各个工艺阶段的混合脉冲模式。项目期间生成的数据基础随后将用于创建描述底层机制的模型概念。基于所获得的结论并使用环保电解液，将在镁基材上生成粘附性低缺陷的混合氧化物涂层，并满足腐蚀性和摩擦学要求的应用。