超高温高韧性(Ta,Nb)2O5-Y2O3-ZrO2热障涂层相平衡及t'相掺杂设计的研究

For the traditional thermal barrier coatings of yttria-stabilized zirconia (YSZ), the phase transition of the tetragonal phase (t') is easy to happen when the temperature is higher than 1300°C, which can result in losing efficacy. Therefore, it is difficult to meet the design requirement of the aero-engine with ultrahigh thrust-weight ratio. The design of new thermal barrier coatings material with higher operating temperature (>1300°C) is a very urgent research task. The Y and R (R:Ta,Nb) co-doped zirconia can improve the operating temperature and reserve the high fracture toughness of the thermal barrier coatings materials. However, only specific co-doping composition can improve the material performance. Accordingly, how to determine the co-doped composition becomes an important scientific issue for the design of new thermal barrier coatings. The present research project focuses on the following aspects in the potential thermal barrier coatings system of (Ta,Nb)2O5-Y2O3-ZrO2: establish the thermodynamic database for this system based on the phase diagram experiment and phase diagram calculation, then discuss the effects of co-doping on the phase stability of tetragonal phase and generalize the scientific law; predict quantitatively the composition region of the t′ phase through theoretical calculation, and screen out the material component material component of TBC for ultrahigh operating temperature (>1300°C). The completion of this project is expected to provide an important theoretical guidance for the design of (Ta,Nb)2O5-Y2O3-ZrO2 based thermal barrier coatings with non-transformation at ultrahigh temperature (>1300°C) and high toughness.

传统氧化钇稳定氧化锆(YSZ)热障涂层中四方相t'在超高温下(>1300°C)容易发生相变而失效，已经难以满足超高推重比航空发动机的设计需求，因此开发具有更高使用温度(>1300°C)的热障涂层材料是十分紧迫的研究任务。Y和R(R:Ta,Nb)共掺杂能提高热障涂层材料使用温度且保留高断裂韧性。然而只有特定的掺杂成分才具有改善材料性能的效果，如何确定掺杂成分成为热障涂层材料设计的重要科学问题。本项目拟以具有潜力的(Ta,Nb)2O5-Y2O3-ZrO2基热障涂层体系为研究对象，基于相图实验和相图计算构筑热力学数据库，探讨共掺杂对四方相稳定性的影响并归纳其科学规律;通过理论计算定量预测t'相形成的成分区域，筛选出适合超高温(>1300°C)使用的热障涂层材料组分。本项目的完成将为(Ta,Nb)2O5-Y2O3-ZrO2基超高温(>1300°C)高韧性热障涂层材料设计提供重要的理论指导。

传统YSZ热障涂层材料在超高温环境下服役容易失效脱落， 已经不能满足新型超高推重比航空发动机的需求，开发具有更高使用温度的新型热障涂层材料是一个十分紧迫的研究任务。本研究通过相平衡法测定了ZrO2-Y2O3-Ta2O5-Nb2O5体系中相关伪二元系和伪三元系的相图。随后耦合本研究和文献综述的实验数据、相图热力学方法和第一性原理计算首次构建了热障涂层材料体系ZrO2-Y2O3-Ta2O5-Nb2O5的热力学数据库。以(Ta, Nb)2O5-Y2O3-ZrO2基热障涂层材料体系为研究对象，探索了三价稀土离子与五价Ta5+或Nb5+共掺杂对四方相氧化锆热稳定性的影响规律，发现较小的掺杂离子更容易促使四方相的形成。基于此，本研究认为ZrO2-YTaO4体系中稳定四方相单相组织或者四方相和单斜钽酸钇的两相组织都是合适的热障涂层掺杂设计方案。此外，本研究形成的氧化物相图的实验测定方案、平台以及实验数据能为以后相关氧化物相图的测定和表征提供借鉴。本研究构建的ZrO2-Y2O3-Ta2O5-Nb2O5热力学数据库能为相关氧化物的相图计算提供基础，并为更高阶的用于CMAS腐蚀研究的热力学数据库提供基础和指导。最后，本项目基于理论计算的新型热障涂层材料体系的开发方案能够为以后热障涂层的设计和开发提供借鉴，并大幅缩短我国新型热障涂层体系的研究周期。