Al2O3/稀土改性的抗CMAS热障涂层微观结构设计与调控

Among the top three prioritized materials research efforts for the development of aerospace heat-insulation technologies, Ni-base single crystal superalloys and thin-film cooling methods have already reached their technological limitations, thus, leaving thermal barrier coatings (TBCs) to be the key technology capable of sustaining further advancement of aero-engines. Coating spallation failures have long been the bottleneck restricting the full utilization of TBCs for heat-insulation. Among these, high temperature corrosion by CMAS plays a critical factor. Being the most established and performance-stable materials choice for TBCs, YSZ is rather vulnerable to CMAS degradation. Although it was found that rare-earth doped YSZ and Al2O3 protection layer on top of YSZ can both react with CMAS to form substances of higher melting temperatures and thus, inhibiting the penetration of molten CMAS as well as preventing Yttria from being leached out of the metastable tetragonal zirconia solid solution, the exact design approach with respect to the composition of rare-earth dopants and Al2O3 protection layer, microstructure engineering, sample preparation and experimental procedures is not well understood. With this in-mind, this research proposal focuses on utilizing first principles calculations to design the composition and microstructure of rare-earth dopants and Al2O3 protection layer, to prepare specimens using a world-class EB-PVD facility, and to investigate microstructure evolution and tailoring mechanisms using the phase field kinetics model. By establishing relationships between the microstructure and materials preparation parameters, the ultimate goal is to develop rare-earth doped and Al2O3 protected YSZ based TBCs having exceptional resistance against CMAS.

世界航空推进计划的三大隔热防护技术中，单晶与冷却气膜技术均已在艰难的挑战极限，热障涂层成为今后航空发动机发展的关键技术。剥落失效是长期困扰和制约热障涂层发展的瓶颈，高温服役环境下CMAS腐蚀是涂层剥落的重要因素。目前应用最成熟、性能最稳定的YSZ热障涂层抗CMAS的能力较低，稀土掺杂、Al2O3隔离层能提高CMAS熔点、抑制CMAS的渗透、Y的析出，是YSZ改性的重要方向。然而，稀土元素成分、隔离层的成分、微观结构如何设计，如何制备并试验微结构的调控，抗CMAS机制的定量分析都还不清楚。基于此，本申请项目基于第一性原理计算设计Al2O3/稀土改性YSZ热障涂层的成分与微观结构，利用国际领先的EBPVD装备与技术探索其制备工艺，基于相场动力学分析热障涂层CMAS腐蚀时微结构的演变与调控机制，并建立微观结构与工艺参数之间的关联，得到抗CMAS性能优异的Al2O3/稀土改性YSZ热障涂层。

本项目的核心内容是通过第一性原理设计Al2O3/稀土改性的YSZ热障涂层成分与微结构，发展Al2O3/稀土改性的热障涂层EB-PVD/APS等制备工艺，并开展其高温CMAS腐蚀的实验分析破坏机制与微结构、工艺、成分之间的关系。项目从2017年至今，建立了Al2O3/稀土改性的YSZ材料抗CMAS/火山灰腐蚀的机制；设计并实现了几种Al2O3/稀土改性YSZ涂层制备，在此基础上提出了用EB-PVD制备多层/掺杂方式YSZ的微结构调控机制；建立了CMAS/火山灰腐蚀热障涂层破坏机制的理论模型，并通过相场法，有限元模拟与实验表征找出了CMAS/火山灰腐蚀失效的关键因素。通过以上研究以及结论，建立了CMAS/火山灰腐蚀失效的关键影响因素与材料设计、制备工艺之间的关联，为TBCs抗CMSA/火山灰腐蚀优化设计提供了可行性思路以及方案。