Damage mechanisms of EB-PVD thermal barrier coatings under combined CMAS and erosion loads

航空发动机和固定式燃气轮机热障涂层（tbc）受到钙镁铝硅（CMAS）沉积损伤的研究日益受到重视。在较低的工作温度下，腐蚀是另一种重要的损坏现象。该项目的最终目标没有改变：揭示CMAS和颗粒侵蚀的复合损伤，获得底层参数之间的系统相关性，发现在这种复杂载荷情况下TBCs的损伤机理。因此，系统地研究了CMAS入渗对EB-PVD tbc侵蚀行为的影响。在第一个资助阶段，我们发现7YSZ的微观结构对CMAS入渗动力学、抗侵蚀能力和复合损伤有很大的影响。有趣的是，渗透TBC在垂直颗粒冲击下的抗侵蚀能力往往以牺牲TBC的机械完整性为代价。这也适用于新型抗cmas涂层，如Gd-zirconate和Al2O3。在温度梯度下，沉积物和TBC的化学性质以及浸润深度的不同决定了TBC中反应相的形成和损伤的进展。首先，渗透过程的分析模型、相的计算（calphhad）和力学性能的测量与实验有很好的定性关联，并为提高涂层的保护性质和损伤预测提供了机会。在第一个资助期成果的基础上，在第二个和最后一个项目阶段同时提高入渗和抗侵蚀能力。这将通过在7YSZ表面使用EB-PVD 65%-YZ (zro2 - 65% wt% Y2O3) tbc和致密或分级的SHVOF-Al2O3涂层来实现。基于真实微结构的三维仿真模型应整合形态对渗透的影响，展现出更科学的改进可能性，更深入地揭示损伤机理。减少沉积物数量的渗透将在温度梯度的循环条件下进行，以在涂层中提供更真实的应力状态。在冲蚀实验中，主要关注的是冲击角和粒径的变化，以模拟类似于涡轮的更真实条件下的损伤过程。对影响侵蚀行为的各种因素进行量化的初步侵蚀模型将通过纳入其他方面而得到扩大；其中大多数还没有足够的数据。这个侵蚀模型将揭示所有因素之间复杂的相互作用。

Damage of thermal barrier coatings (TBCs) in aero-engines and stationary gas turbines by deposits of calcia-magnesia-alumina-silica (CMAS) has gained increasing importance. At lower operating temper-atures erosion is another important damage phenomenon. The ultimate goal of this project is un-changed: to reveal the combined damage by CMAS and particle erosion, to get systematic correlations between the underlying parameters, and to discover the damage mechanisms of the TBCs under this complex loading situation. Therefore, the impact of CMAS infiltration on the erosion behavior was studied systematically for EB-PVD TBCs. In the first funding period it was found that the microstructure of 7YSZ has a large impact on CMAS infiltration kinetics, erosion resistance, and on the combined damage. Interestingly, the erosion resistance of infiltrated TBCs under perpendicular particle impact was often improved at the expense of mechanical integrity of the TBC. This is also valid for novel CMAS-resistant coatings such as Gd-zirconate and Al2O3. The chemistry of both deposit and TBC, and infiltration depth that would be different under a temperature gradient rule the formation of reaction phases and damage progression in the TBCs. First analytical models for the progress of infiltration, calculation of phases (Calphad), and measurements of mechanical properties correlate qualitatively well with experiments and open opportunities for improving the protective nature of the coatings and prediction of damage. Based on the results from the first funding period, both infiltration and erosion resistance shall be improved simultaneously during the second and final project phase. This will be achieved by using EB-PVD 65%-YZ (ZrO2-65 wt% Y2O3) TBCs and dense or graded SHVOF-Al2O3 coatings on top of 7YSZ. 3D simulation models based on real microstructures shall integrate the influence of morphology on infiltration, unfold more scientific based possibilities for further improvements and reveal the damage mechanisms in more depth. Infiltration by a reduced number of deposits will be performed under cyclic conditions in a temperature gradient to provide more realistic stress states in the coating. For the erosion experiments variation of both impact angle and particle size are within the main focus to simulate the damage progression under more realistic conditions that are similar to a turbine. The preliminary erosion model that quantifies various factors affecting the erosion behavior will be enlarged by incorporating additional aspects; for most of them sufficient data are not yet available. This erosion model will then reveal the complex interaction between all factors.