应变幅和相角度对热障涂层材料系统热机械疲劳性能的影响

The Effect of Strain Range and Phase Angles on the Thermomechanical Fatigue Properties of Thermal Barrier Coating System

摘要:

热障涂层作为燃气轮机高温部件的关键材料,其服役过程中的脱落与失效机理一直是研究的热点问题。本文主要研究了应变幅和相角度对含热障涂层的镍基高温合金热机械疲劳性能的影响。研究结果表明,在相同相角度下,热机械疲劳寿命随应变幅的增大而降低。固定应变幅,同相位下样品的热机械疲劳寿命要高于反相位样品。所有样品中,裂纹萌生于热生长氧化物层,在粘结层与陶瓷层界面扩展形成分层裂纹,分层裂纹与陶瓷层内贯穿裂纹连接起来导致大面积的陶瓷层剥落,从而导致TBC层失效。另外,本文分析了热障涂层中的应力分布,初步建立了含热障涂层的镍基高温合金热机械疲劳寿命模型,发现含热障涂层的镍基高温合金热机械疲劳寿命与涂层中的最大应力呈指数关系。

Abstract:

As the key material of components used in elevated temperature of gas turbines, the mechanism of delamination and failure of thermal barrier coatings (TBCs) under service conditions has been the hot spot of research for a long time. The influences of strain ranges and phase angles on the thermomechanical fatigue (TMF) properties of samples with thermal barrier coatingsTBCs were investigated in this paper. It was is shown that under the same phase angles, the TMF lifetime decreased decreases with the increase of strain ranges. Under the same strain range, the in-phase tests had have longer TMF lifetime than out-of-phase tests. In both samples, cracks were are initiated in thermally grown oxide (TGO) layer, and then propagated along the bond coat/ceramic top coat, forming the delamination cracks. When the delamination cracks connected with the segmentation cracks initiated in ceramic coat, the TBCs spalled. A TMF lifetime model concerning strain ranges and phase angles was is established, and an exponential law exists between TMF lifetime and the maximum stress