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（TBCs）中的钙镁铝硅（CMAS）沉积物的损坏越来越受到重视。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和颗粒侵蚀的联合损伤，获得基础参数之间的系统相关性，并发现TBC在这种复杂加载情况下的损伤机制。因此，本文系统地研究了CMAS熔渗对EB-PVD热障涂层冲蚀磨损性能的影响。在第一个资金期间，人们发现，7 YSZ的微观结构有很大的影响CMAS渗透动力学，耐侵蚀性，并在组合损伤。有趣的是，渗透热障涂层在垂直粒子冲击下的耐冲蚀性往往是以热障涂层的机械完整性为代价来提高的。这也适用于新型抗CMS涂层，如Gd-锆酸盐和Al 2 O3。存款和TBC的化学性质，以及在温度梯度下不同的渗透深度，决定了热障涂层中反应相的形成和损伤的发展。第一个分析模型的渗透，计算阶段（Calphad），和测量的机械性能的进展相关的定性以及与实验和开放的机会，以提高涂层的保护性和预测的损害。根据第一个供资期的结果，在第二个也是最后一个项目阶段，应同时提高抗渗透性和抗侵蚀性。这将通过使用EB-PVD 65%-YZ（ZrO 2 -65 wt% Y2 O3）TBC和在7 YSZ顶部上的致密或分级SHVOF-Al 2 O3涂层来实现。基于真实的微观结构的三维模拟模型应综合考虑形态对渗透的影响，为进一步改进提供更科学的依据，并更深入地揭示损伤机理。通过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。对于侵蚀实验，主要关注冲击角度和颗粒尺寸的变化，以模拟与涡轮机相似的更真实条件下的损坏进展。将通过纳入其他方面来扩大量化影响侵蚀行为的各种因素的初步侵蚀模型;对于其中大多数方面，尚没有足够的数据。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.