稀土复合氧化物热障涂层的抗CMAS机理研究

Thermal barrier coatings (TBCs) are widely used in gas turbines to provide thermal insulation protection for the high-temperature components, which can effectively decrease the temperature of superalloy substrate, giving rise to a prolonged service life. With the increase of turbine inlet temperature, the early spalllation of TBCs caused by CMAS infiltration is becoming a critical issue influencing the reliability of gas turbines. As an important TBCs candidate, R2(Zr0.7Ce0.3)2O7 (RZ7C3，R=La, Nd, Sm, Gd, Y, Yb) shows extremely low thermal conductivity and high sintering resistance. Besides, RZ7C3 also has the potential to resistant CMAS attack. In this project, we will make comprehensive studies on the CMAS resistance mechanisms of RZ7C3 coatings. The composition effects and microstructure effects on CMAS resistance ability of the RZ7C3 coatings will be explored. The chemical and mechanical stability of the double-ceramic-layer coatings and the graded coatings based on RZ7C3 and YSZ will be investigated in the presence of thermal gradient and CMAS deposits. From these studies, the failure mechanisms of RZ7C3 coatings under thermo-mechanical-chemical loadings will be revealed, which can provide the valuable theoretical basis for the design of CMAS resistant TBCs. By choosing appropriate coating compositions and microstructures, RZ7C3 TBCs with high thermal insulation/good thermal cycling life/excellent CMAS resistance ability can be prepared, which will have important theoretical and technical significances to promote this kind of coatings for industrial applications.

热障涂层（TBCs）是沉积在高温部件表面的热防护涂层，可以有效降低金属部件的温度并延长其使用寿命。随着燃气轮机工作温度的不断提高，TBCs的CMAS高温腐蚀失效成为影响发动机可靠性的关键因素。作为一种重要的TBCs候选材料，R2(Zr0.7Ce0.3)2O7 (RZ7C3，R=La, Nd, Sm, Gd, Y, Yb)具有极低的热导率、优异的抗烧结性能，和较好的抗CMAS腐蚀潜力。本项目系统研究RZ7C3涂层抗CMAS机理的关键基础问题，包括稀土元素种类、微观组织结构对RZ7C3涂层抗CMAS性能的影响规律及作用机制，热梯度作用下RZ7C3/YSZ双陶瓷层结构和梯度结构TBCs关键界面在CMAS环境中的热化学/热机械稳定性等，为抗CMAS涂层的设计提供理论依据。通过成分设计和结构调控，实现RZ7C3涂层高隔热/长寿命/抗CMAS功能一体化，为推动该类涂层走向工业应用奠定理论与技术基础。

热障涂层（TBCs）沉积在燃气轮机热端部件表面，可以显著提高其服役温度和抗高温氧化能力，从而大幅提高发动机的热效率和性能。然而，TBCs在服役过程中不可避免会受到CaO-MgO-Al2O3-SiO2（CMAS）的影响。随着涡轮进口温度的不断提高，CMAS高温腐蚀已成为制约TBCs服役性能及可靠性的关键因素。作为一类重要的TBCs候选材料，R2Zr2O7、R2Ce2O7和R2(Zr0.7Ce0.3)2O7 (RZ7C3，R=La, Sm, Gd, Y, Er,Yb)具有极低的热导率、优异的抗烧结性能，和较好的抗CMAS腐蚀潜力。本项目系统研究了稀土元素种类、微观组织结构对稀土复合氧化物涂层抗CMAS性能的影响规律及作用机制，分析了热梯度作用下RZ7C3/YSZ双陶瓷层结构TBCs关键界面在CMAS环境中的热化学/热机械稳定性。结果表明，R2Zr2O7和RZ7C3的抗CMAS性能与生成的磷灰石相的成分变化一致，稀土离子半径越小，晶化CMAS效率越高，抗CMAS性能也越好；对于R2Ce2O7，由于大量的Ce参与形成磷灰石相，因此R2Ce2O7晶化CMAS效率显著高于R2Zr2O7和RZ7C3。此外，R2Ce2O7与CMAS反应最初只有磷灰石相一种产物，更容易形成致密结构，有利于阻挡 CMAS渗透，因此R2Ce2O7的抗CMAS性能显著优于R2Zr2O7和RZ7C3。R2Ce2O7的抗CMAS性能与磷灰石相的稳定性有关，稀土离子半径与Ce4+越接近，磷灰石相的稳定性越高，抗CMAS性能也越好。Gd2Ce2O7具有最好的抗CMAS性能，相同条件下CMAS腐蚀深度仅为的约1/10。本项目的相关研究成果可以为抗CMAS热障/环境障碍涂层的设计提供理论依据。