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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

本文对某陆基燃气轮机高温部件热障涂层的断裂过程和疲劳行为进行了实验和分析研究。采用有限元法和各种循环剪切、拉伸和扭转试验，通过对面涂层残余应力的测量，研究了热载荷对涂层厚度和分层强度的影响。结果表明：(1)900℃和1000℃时，TGO层厚度随加热时间的增加而增加，20 h后逐渐饱和。(2)在热载荷作用下，面漆与粘结层界面的波动峰值处发生面漆分层。这是因为在冷却后的峰值区域出现了垂直于界面的拉伸撕裂应力。因此，对于tbc的破坏模式，我们可以发现两种模式，第一种模式是裂纹在TC表面萌生并沿厚度方向扩展。当更多的裂纹到达界面附近后，界面处发生分层并扩展。另一种模式是，可以观察到局部分层，而没有从TC表面生长出任何裂纹。在这两种情况下，可以观察到分层从界面附近的BC波动的一个峰到另一个峰。(3)发现热老化后粘结层的力学性能发生变化，粘结层强度对tbc的剪切疲劳行为有影响。(4)分层能量随着加热时间的增加迅速增加，加热时间达到40 h后，分层能量略有下降。因此，经长时间加热后，碳化钨的分层强度明显降低。这是因为随着加热时间的延长，TC内的残余应力增大，因此弹性应变能增大。(5)长时间加热导致BC软化，使tbc的疲劳寿命小。(6)我们可以发现，用小试样剪切得到的分层强度数据可靠，散射带小。(7)扭转销试验是获得热喷涂涂层在剪切和拉应力联合作用下分层强度的较好方法。少