热循环下梯度热障涂层热氧化物生长的应力分析
Numerical analysis of thermal stress for gradient thermal barrier coatings experienced thermal oxidation growth under thermal cycle
黄孝庆，黄护林
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作者单位：南京航空航天大学高新技术研究院
中文关键字：热障涂层； 热应力； 梯度涂层； 热生长氧化物；有限元法
英文关键字：thermal barrier coating system（TBCs）；thermal stress；functionally gradient coatings；Thermal growth oxidation；finite element method
中文摘要： 建立了一种预测多层复合梯度热障涂层热应力的理论模型，并通过有限元方法分析了梯度涂层分布指数n、热循环过程中热氧化物的生长对涂层热应力大小及分布的影响。研究结果表明，通过控制梯度涂层的成分分布指数n可以显著降低热应力和改善应力分布。当n=1时，涂层热应力较小且变化平缓，结合性能优异。与双层非梯度涂层的热应力对比可知，功能梯度涂层能显著地缓和涂层系统的热应力和消除应力集中。另外，热循环过程中梯度热障涂层与基体界面附近生长的热氧化物急剧地提升了界面附近的热应力，复杂而又集中的热应力对梯度涂层有很大的破坏。同时采用了一种方法来抑制热氧化物的生长，结果显示该方法能较好地优化涂层的热应力和改善涂层质量。
英文摘要： A multi-layer numerical model was proposed in order to predict the thermal stress of multi-layer gradient thermal barrier coating system (TBCs). Based on the finite element method, the effects of compositional exponent and the thermal oxidation which grown in thermal cycling process on the thermal stress and the distribution of TBCs were investigated. The results showed that it is feasible to mitigate thermal stress and improve the stress distribution by controlling compositional exponent n of the coatings. When n =1, thermal stress were low and gentle change, and the coatings performance excellent. Compared with non-gradient duplex coatings, functionally gradient coatings were able to alleviate the thermal stress and suppress stress concentration of TBCs significantly. In addition, under the thermal cycling process, the thermal growth oxidation located in the interface of gradient coatings and the substrates had dramatically enhanced the interface thermal stress. Complex and concentrated thermal stress had a tremendous damage to the gradient coating system. So a method was proposed to prevent the growth of thermal oxide, the results demonstrated that the method could be contributed to optimize thermal stress and improve the quality of the coatings.