Influence of water vapor on the useable lifetime of thermal barrier coatings (TBCs) on high temperature components in gas turbines

在不久的将来，燃气轮机中的氢燃烧将在减少二氧化碳排放方面发挥重要作用。燃料气体中氢含量的增加导致使用的材料面临许多挑战，例如，现代燃气轮机中使用的热障涂层。在本项目中，将研究水蒸气对最常用的热障涂层材料钇稳定氧化锆（YSZ）性能的影响。尽管这种材料已经在商业上用于涡轮机几十年了，但关于水蒸气影响的知识是有限和矛盾的。因此，本项目旨在研究含有水蒸气的气氛对热障涂层性能的影响。考虑了常用的大气等离子喷涂（APS）和悬浮等离子喷涂（SPS）系统。这两种体系都有其特有的微观结构特征（孔隙度、微裂纹、柱状结构），这对性能尤其是使用寿命至关重要。一方面，将研究水蒸气对独立涂层烧结的影响，并利用高分辨率表征方法分析其基本过程。烧结导致弹性模量的增加，从而导致更高的应力和热障涂层系统的早期失效。除烧结外，还将阐明对YSZ不良相变的影响。从文献中清楚地记录了水蒸气对YSZ相变的影响，但缺乏对热障涂层的详细研究。除了在独立涂层上进行的这些研究之外，还将检查完整的热障涂层系统（基材+粘结层+热障涂层）在水蒸气中的行为。冷却条件在这里也有变化，因为已知它们对相变有影响。最终，所获得的知识应该一起流动，并使水蒸气对等离子喷涂ysz基热障涂层使用寿命的影响有可能做出明确的陈述。

Hydrogen combustion in gas turbines will play an important role in reducing CO2 emissions in the near future. An increasing hydrogen content in the fuel gas leads to a number of challenges in the materials used, e. g. also the thermal barrier coatings used in modern gas turbines. In this project, the influence of water vapor on the properties of the most commonly used thermal barrier coating material, yttria-stabilized zirconia (YSZ), will be investigated. Although this material has been used commercially in turbines for decades, knowledge about the influence of water vapor is limited and contradictory. Therefore, this project aims to investigate the influence of atmospheres containing water vapor on the properties of thermal barrier coatings. The commonly used atmospheric plasma sprayed (APS) and suspension plasma sprayed (SPS) systems are considered. Both systems have characteristic microstructural features (porosity, microcracks, columns) that are essential for the properties and especially the service life. On the one hand, the influence of water vapor on the sintering of free-standing coatings will be investigated and the underlying elementary processes will be analyzed using high-resolution characterization methods. Sintering leads to an increase in the modulus of elasticity and thus to higher stresses and earlier failure of thermal barrier coating systems. In addition to sintering, the influence on the undesired phase transformation of the YSZ will also be clarified. An influence of water vapor on phase transformations in the YSZ is clearly documented from the literature, but detailed investigations on thermal barrier coatings are lacking. In addition to these investigations, which are carried out on free-standing coatings, complete thermal barrier coating systems (substrate + bond coat + thermal barrier coating) will also be examined for their behavior in water vapor. The cooling conditions are also varied here, as it is known that they have an influence on the phase transformations. Ultimately, the knowledge gained should flow together and make it possible to make a clear statement on the influence of water vapor on the service life of plasma-sprayed YSZ-based thermal barrier coatings.