Finite element simulation of stresses in a plasma-sprayed thermal barrier coating with a crack at the TGO/bond-coat interface
Finite element simulation of stresses in a plasma-sprayed thermal barrier coating with a crack at the TGO/bond-coat interface
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DOI：
10.1016/j.surfcoat.2018.01.024
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发表时间：
2018-03
影响因子：
5.4
通讯作者：
P. Skalka;K. Slámečka;J. Pokluda;L. Čelko
中科院分区：
文献类型：
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作者：
P. Skalka;K. Slámečka;J. Pokluda;L. Čelko
等离子体喷涂的热障涂层通常由陶瓷顶涂层和具有不规则金属/陶瓷界面的金属粘结涂层组成，这是更好的粘附所需的，同时产生导致使用中失效的拉伸应力。暴露于高温导致在顶涂层/粘合涂层界面处形成第三薄的热生长氧化物（TGO）层。在这些涂层中实验观察到的开裂机制之一是在TGO/粘结涂层界面峰处的分层。这种分层裂纹增加了陶瓷顶涂层中的拉伸应力，并可能导致其开裂。本文对传统等离子喷涂TBC系统中YSZ（氧化钇部分稳定氧化锆）顶层涂层的残余应力状态进行了数值研究，该涂层具有以TGO/粘结层三维余弦界面峰为中心的分层裂纹。结果表明，分层裂纹在YSZ层中产生了较大的应力，小的界面峰更容易在峰上产生裂纹，而大的界面峰更容易在峰外产生裂纹。此外，它表明，纵横比（振幅与波长的比率），这是经常使用的数值研究，以区分各种几何形状，是不是一个唯一的参数，因为振幅和波长的变化是不相等的。
Plasma-sprayed TBCs typically consist of a ceramic top-coat and a metallic bond-coat with an irregular metal/ceramic interface, which is required for better adhesion and, at the same time, generates tensile stresses responsible for in-service failure. Exposure to high-temperatures results in formation of a third, thin layer of thermally grown oxide (TGO) at the top-coat/bond-coat interface. One of the cracking mechanisms experimentally observed in these coatings is delamination at the TGO/bond-coat interfacial peaks. Such delamination cracks increase tensile stresses in the ceramic top-coat layer and may induce its cracking. This article provides the numerical study of the residual stress state of the YSZ (yttria partially-stabilized zirconia) top-coat in a conventional plasma-sprayed TBC system with a delamination crack centred at the TGO/bond-coat 3D cosine interfacial peak. The results show that the delamination crack induces considerable stresses in the YSZ layer; the small interfacial peaks are more likely to cause cracking above the peak, whereas the large peaks are more likely to cause off-peak cracking. Furthermore, it is shown that the aspect ratio (the ratio of amplitude to wavelength), which is often used in numerical studies to distinguish between various geometries, is not a unique parameter, since the changes in amplitude and wavelength are not equivalent.