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，因此在减轻移动的系统重量方面具有巨大的潜力。除此之外，镁很容易回收。卓越的铸造工艺性能和对电磁和机械振荡的良好阻尼能力注定了镁材料用于机械外壳的构造以及可感知的感官、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性能，但由于镁合金对腐蚀和摩擦应力的抵抗力较低，目前镁合金的应用范围受到限制。等离子体电解氧化是一种有前途的环境友好的表面处理工艺，以应对这些技术挑战。一个已经成功完成的DFG项目关注的是放电开始之前和放电过程中的基质/电解质相互作用，以及电解质组分插入到生成的PEO涂层中的目标。结果表明，通过采用高浓度的电解质，非常硬和耐化学腐蚀的混合氧化物（化学成分主要由电解质成分，而不是基板成分）涂层是可生产的，其硬度超过MgO层显着。然而，由于它们的形态受到局部缺陷的影响，这样的涂层将对所得的耐腐蚀性和耐磨性产生负面影响。这表明需要进一步研究。在等离子体电解质涂覆过程期间，根据现有技术并且在缺乏一致的工艺模型的情况下，复杂的涂层形成工艺以及化学和电工艺参数的相互作用的表征仅可能通过经验手段。因此，本项目旨在研究镁等离子体电解氧化过程中形成混合氧化物时化学和电学过程相互作用的作用机理。为了实现这一目标，需要详细描述和理解这一过程。为此，需要将涂层形成所需的脉冲电荷吞吐量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愈合软停车和阴极放电等特定工艺阶段。在此基础上，将开发针对各个工艺阶段调整的混合脉冲模式。项目期间生成的数据基础随后将用于创建描述基本机制的模型概念。基于所获得的结论，并使用环境友好的电解质，粘附和低缺陷的混合氧化物涂层是在镁基材上产生的，并有资格为腐蚀和摩擦学要求高的应用。