Study on Delamination Fatigue Strength of Thermal Barrier Coating at Elevated Temperature

热障涂层高温分层疲劳强度研究

基本信息

批准号：
20560087
负责人：
KANEKO Kenji
金额：
$ 3.08万
依托单位：
Tokyo University of Science
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2008
资助国家：
日本
起止时间：
2008 至 2010
项目状态：
已结题

项目摘要

In this study, it is investigated experimentally and analytically that fracture process and fatigue behavior of Thermal Barrier Coatings (TBCs) used in a high temperature component in a land based gas turbine. The effects of the thermal load on TBCs and delamination strength are investigated by measuring residual stress of top coat, using the finite element method and various cyclic shearing, tensile and torsion tests.It is found that (1)the TGO layer thickness increases with increasing heating time for both cases of 900 and 1000℃, and it saturates gradually after 20 hours for the both cases. (2)A delamination of top coat under thermal load occurs at a peak of undulation in top coat and bond coat interface. This is because that tensile tearing stress which is normal to the interface occurs at the peak area after cooling. So, about failure patterns of TBCs, we can find two patterns, the first one is that a crack initiates at TC surface and propagates in the thickness direction. After th … More e crack arrives near the interface, a delamination occurs at the interface and grows. Another pattern is that a local delamination can be observed without any crack grown from the TC surface. In the both cases, it is observed that delaminations run from a peak to peak of undulation of BC near the interface. (3)It is found that the mechanical property of bond coat changes after thermal aging and the shear fatigue behavior of TBCs is affected by bond coat strength. (4) Delamination energy increases quickly with increasing heating time up to 40 hours and then decreases slightly. So, the delamination strength of TC is thought to decrease apparently after long time heating. This is because that residual stress in TC increases and so elastic strain energy increases with increasing heating time. (5) Softening of BC caused by long heating makes fatigue life of TBCs small.(6)We can find that the shearing using small plating specimens gives reliable data with small scatter bands on delamination strength. (7)Also, the torsion pin-test was found to be a good method which obtains a delamination strength of thermal sprayed coating under combined shearing with tensile stresses. Less

在本研究中，通过实验和分析方法研究了陆基燃气轮机高温部件中使用的热障涂层 (TBC) 的断裂过程和疲劳行为。通过以下方法研究了热载荷对 TBC 和分层强度的影响。采用有限元法和各种循环剪切、拉伸和扭转试验测量面涂层的残余应力。发现(1)在900℃两种情况下，TGO层厚度都随着加热时间的增加而增加。 1000℃和1000℃，两种情况均在20小时后逐渐饱和。 (2)热负荷下面漆分层发生在面漆和粘结层界面的波动峰值处。垂直于界面的裂纹发生在冷却后的峰值区域，因此，关于热障涂层的失效模式，我们可以发现两种模式，第一种是在TC表面出现裂纹，并在厚度方向上扩展。更多的裂纹到达界面附近，在界面处发生分层并生长。另一种模式是可以观察到局部分层，而没有任何裂纹从 TC 表面生长。在这两种情况下，都观察到分层从峰值开始。 (3)发现热老化后粘结层的力学性能发生变化，并且TBC的剪切疲劳行为受到粘结层强度的影响。(4)分层能随着增加而迅速增加。加热时间到到40小时后略有下降，因此，长时间加热后，TC的分层强度明显下降，这是因为TC的残余应力随着加热时间的增加而增加，因此弹性应变能增加。长时间加热引起的BC使TBC的疲劳寿命变短。(6)我们可以发现，使用小电镀样品的剪切给出了可靠的数据，其分层强度的分散带很小。(7)此外，还发现了扭力销试验。是一种获得热喷涂层在拉应力联合剪切下的分层强度的好方法。