Development of novel creep resistant bond coats for “Environmental Barrier Coatings”

碳化硅纤维增强碳化硅复合材料作为高温材料，在飞机发动机和固定式燃气轮机中具有很高的应用潜力。与镍基高温合金相比，sic复合材料可以实现更高的进口温度。在飞机发动机和固定式燃气轮机的应用条件下，sic复合材料的组件必须使用环境屏障涂层（EBC）系统来防止水蒸气引起的损失。现代EBC系统的寿命主要取决于硅结合层的性能。硅结合层的高抗蠕变性能对整个EBC体系非常重要。本项目的目的是为现代EBC系统开发具有增强抗蠕变性能的新型硅基结合涂层。这样可以延长EBC系统的使用寿命。在这个项目的范围内，材料和工艺技术方面的新发展将会实现这一目标。新型模具涂层材料将以Si/Si3N4-和Si/ sic -复合材料为基础。这些复合材料通过Si3N4和sic的增强，提高了硅基涂层的抗蠕变性能。增加的抗蠕变能力将延长粘结层上热生长氧化物（TGO）垢的寿命，从而延长整个EBC系统的寿命。相应的喷雾粉末将被设计和开发。结合层将通过等离子喷涂和HVOF喷涂来生产。模具喷射参数将发展为两种喷射工艺，以产生致密和均匀的微结构。除了表征微观结构和相组成以及研究机械和热物理性能外，还将通过等温暴露和高温（如T= 1300°C）的热循环测试来研究新型粘结涂层的tgo形成、生长和损伤机制。最后，研究了通过热处理进一步改善涂层性能的可能性。

SiC-fiber reinforced SiC-composites as high temperature materials exhibit high potential for applications in aircraft engines as well as stationary gas turbines. The SiC-composites can realize higher inlet temperatures compared with Ni-based superalloys. Under application conditions both in aircraft engines and in stationary gas turbines the components of SiC-composites must be protected against water vapor induced losses using an environmental barrier coating (EBC) system. The life time of modern EBC systems depends among others on the properties of the Si bond coat. A high creep resistance of the Si bond coat is very important for the whole EBC system. The purpose of this project is the development of novel Si-based bond coats for modern EBC systems with enhanced creep resistance. In this way, the life time of the EBC system will be increased. Within the scope of this project, new developments with respect to materials and process technology will be carried out to achieve the aim. Die novel coating materials will be based on Si/Si3N4- and Si/SiC-composites. These composites can increase the creep resistance of the Si-based bond coats due to Si3N4- and SiC-reinforcing. The increased creep resistance will enhance the life time of the thermally grown oxide (TGO) scale on the bond coat and thus of the whole EBC system. The corresponding spray powders will be designed and developed. The bond coats will be produced by plasma spraying as well as by HVOF spraying. Die spray parameters will be developed for both spray processes to produce dense and homogenous microstructures. In addition to a characterization of the microstructures and phase compositions and investigation of the mechanical and thermo-physical properties, the novel bond coats will be investigated with regard to TGO-formation, -growth and damage mechanisms by isothermal exposition and by thermal cyclic tests at high temperatures of such as T=1,300 °C. Finally, the possibility of further improvement of the coating properties by heat-treatment will be studied as well.