新型纳米晶/YSZ热障涂层的高温氧化机理研究

The high temperature coating, represented by thermal barrier coating, has become one of the key technologies for the development of advanced engines. Due to the formation of non-protective oxides on the surface of traditional bond coating (β2 or MCrAlY coatings), numerous stress come out as the oxidation growth rate fast increased. So the ceramic top coating (YSZ) has an easily trend to crack and peel off along the oxide film. When in service performance is not adequate and stable, and it is urgent to develop a novel high temperature bond coating with thermodynamic stability as an alternative. It is remarkable that magnetron sputtering nanocrystalline coating has unique structure and composition characteristics. The high-density defects in nanocrystalline structure promote selective oxidation of Al and the formation of dense and intact Al2O3 scale, and reduce the growth rate of the oxide film and the internal stress, which provides a high resistance against high-temperature oxidation for alloys. Besides, it has a same columnar structure as the top coating by EB-PVD, which is conductive to the release of internal stress. Therefore, the spallation resistance and stable of TBC can be improved. On this account, the nanocrystalline coating has become a great potential for the bonding coating of TBC. However, there is no detailed research and discussion on the compatibility between nanocrystalline coating and YSZ top coating. The high temperature protection performance and the underlying mechanism is also unclear. In this project, a novel thermal barrier coating system with the bond coating of nanocrystalline coating will be prepared on single crystal superalloy. The high temperature oxidation kinetics and thermodynamics of coatings are researched. Based on this, the evolution process of two active interfaces controlled by diffusion is illustrated, and the high temperature oxidation behavior and degradation mechanism of the coatings are established, which provide guidelines and the theoretical foundation for the application of novel TBC systems.

以热障涂层为代表的高温防护涂层技术已成为先进发动机研制的关键技术之一。由于传统金属粘结层NiCrAlY表面非保护性氧化物的生成，在严苛高温环境下氧化膜的生长速度快，产生应力大，陶瓷层（YSZ）易沿氧化膜开裂、剥落而导致服役寿命严重下降，亟需开发一种热力学稳定的新型高温粘结层作为替代。磁控溅射纳米晶涂层具有独特的结构与成分特点，其纳米晶结构可促进铝的选择性氧化，降低氧化膜的生长速度及内应力；此外，与（电子束沉积的）陶瓷层相同的柱状结构，有利于内应力的释放，亦可提高氧化膜的抗剥落能力，具有成为热障涂层粘结层的巨大潜力。然而，当前并无任何关于纳米晶涂层与YSZ陶瓷层界面相容性、高温防护性能等内容的详细研究和探讨。本项目拟通过新型纳米晶热障涂层高温氧化动力学和热力学研究，揭示涂层两处活性界面的服役演化规律，完成新型热障涂层高温氧化行为和退化过程机理研究，为新型热障涂层设计与开发提供理论支撑。

纳米晶结构可促进铝的选择性氧化，为合金提供优异的抗高温氧化性能。利用该特点制备的与合金基体同成分的纳米晶涂层，还可避免传统金属涂层所遇到的界面互扩散问题，服役过程中不影响基体合金的组织结构及力学性能，开发新型纳米晶热障涂层体系，具有独特的科学研究价值和重要的应用前景。通过纳米晶粘结层热障涂层高温氧化动力学及TGO生长规律热力学研究，深入分析纳米晶涂层对界面稳定性与抗氧化性能提升的作用本质：研究了YSZ陶瓷层/纳米晶涂层高温服役过程中元素扩散行为及分布特性，分别探索两处界面的微观组织结构演变规律；开展了纳米晶粘结层生长的TGO的粘附性与其应力响应机制研究；分析获得热障涂层经长期热循环后各层成分结构演化规律同其退化过程的联系。.通过该项目的资助，在纳米晶涂层高温防护机理研究的基础之上，掌握了新型纳米晶/YSZ热障元素涂层的设计原理和制备科学，并与中航发黎明公司合作，开展了发动机工况下纳米晶涂层的性能模拟研究。项目执行三年时间内，发表了SCI收录论文共9篇，培养博士毕业研究生2名，在读博士生1名，在读硕士研究生1名。