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Embrittlement of gamma titanium aluminides by high temperature oxidation: mechanisms and abatement measures

高温氧化导致γ钛铝化物脆化：机理和减缓措施

基本信息

批准号：
272900143
负责人：
Privatdozent Dr.-Ing. Mathias Galetz
金额：
--
依托单位：
Institut für Werkstoffwissenschaft
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2015
资助国家：
德国
起止时间：
2014-12-31 至 2019-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/272900143?language=en
关键词：
Embrittlement gamma titanium aluminides temperature

项目摘要

The primary objective of the proposal is to tune the surface of gamma TiAl in such a way that thermal barrier coatings can be applied to TiAl components without impairing the mechanical properties of the base material or even with improving them compared to the uncoated state. For this purpose, aluminide (= aluminum diffusion coating) and cathode-sputtered TiAl layers are applied on top of the titanium aluminide alloys followed by halogenation, so that a protective aluminum oxide top layer is formed during the subsequent heat treatment, which acts as a diffusion barrier to prevent further oxygen induced embrittlement. To reach this objective, the influence of the thermal loading during the individual process steps such as pre-oxidation and application of the thermal barrier coating as well as a subsequent high temperature ageing on the microstructure and properties in the subsurface zone have to be fundamentally investigated. Based on this, a mechanistic understanding of degradation and suitable strategies for suppressing subsurface embrittlement are developed. Based on the results of the first two-year project phase, the coating parameters, including composition and thickness of the barrier layers, are to be optimized in the final third year. The evaluation of the lifetime of the coating systems under high temperature stress as well as the completion of the investigations of the mechanical properties of selected variants are in the focus. First promising fatigue measurements show that magnetron sputtered layers with halogenation reduce oxygen embrittlement due to the Al enrichment. The investigations carried out so far have shown that a high proportion of the beta(o)-phase in the starting structure can be classified as particularly critical with regard to embrittlement due to the oxygen-induced conversion into alpha2. Therefore, in the second phase of the project, additional investigations are to be carried out on a Ti-48Al-2Cr-2Nb alloy (available at the partners), since this alloy has a low content of beta(o)-phase. After a profound analysis of the embrittlement mechanism and the effect of the coating systems, selected specimens will be mechanically tested to verify the improved properties of the low beta phase alloy with the protection system.

该提案的主要目标是调整γ TiAl 的表面，使得热障涂层可以应用于TiAl 部件，而不会损害基材的机械性能，甚至与未涂层状态相比有所改善。为此，将铝化物（=铝扩散涂层）和阴极溅射 TiAl 层涂覆在钛铝化物合金的顶部，然后进行卤化，以便在随后的热处理过程中形成保护性氧化铝顶层，该保护层充当扩散阻挡层，以防止进一步的氧诱导脆化。为了实现这一目标，必须从根本上研究各个工艺步骤（例如预氧化和热障涂层的应用以及随后的高温时效）期间热负荷对地下区域的微观结构和性能的影响。在此基础上，开发了对退化的机械理解和抑制地下脆化的合适策略。根据第一个两年项目阶段的结果，涂层参数，包括阻挡层的成分和厚度，将在最后的第三年进行优化。重点是评估涂层系统在高温应力下的寿命以及完成所选变体的机械性能研究。第一个有希望的疲劳测量表明，具有卤化作用的磁控溅射层可减少由于富铝而导致的氧脆化。迄今为止进行的研究表明，起始结构中高比例的 β(o) 相可被归类为对于由于氧诱导转化为 α2 导致的脆化特别关键。因此，在项目的第二阶段，将对Ti-48Al-2Cr-2Nb合金（可从合作伙伴处获得）进行额外的研究，因为该合金的β(o)相含量较低。在对脆化机制和涂层系统的影响进行深入分析后，将对选定的样品进行机械测试，以验证具有保护系统的低β相合金的改进性能。