Mechanics and Mechanisms on Adhesion of Thermal Barrier Coating : Towards Improvement and Design of Thermal Fatigue Endurance.

高性能热障涂层是新一代先进燃气轮机在极高温度下运行的必备材料。为了提高和设计热障涂层的耐热疲劳性能，针对热障涂层中陶瓷涂层的力学性能，特别是弹性模量的评价；工艺参数的影响(S)；陶瓷涂层与镍基高温合金基板的结合强度有多高以及如何评价；热障涂层中的残余应力有多大以及如何评价等问题，进行了一系列的实验研究。空气等离子喷涂(APSED)YSZ(；ZrO2)的弹性硬度稳定在8wt.%。采用宏观、微观和纳米压痕方法对先进燃气轮机热障涂层(TBC)系统常用的Y_2O_3)面层样品进行了测试。根据Oliver-Pharr方法测量弹性刚度。结果表明，喷涂条件对YSZ的弹性刚度和显微组织有显著影响。尤其是所用陶瓷粉末的大小对其影响最为显著。研究还表明，弹性刚度表现出显著的尺寸效应：即宏观、微观和纳米压痕方法的弹性刚度存在显著差异。讨论了上述尺寸效应与压痕过程中的一些相关现象：裂纹、凹陷、堆积和剥落，以及喷涂层的特征组织。在此基础上，重点讨论了开发高性能热障涂层应控制哪种组织类型，以及如何通过控制喷涂工艺参数来实现这一目标。

Thermal barrier coatings (TBCs) with high performance have been essential for next generation advanced gas turbines operating at extremely high temperatures. Towards improvement and design of thermal fatigue endurance of TBCs, a series of experimental works have been carried out to get basic understandings on the following articles : how the mechanical properties of ceramic top coat film in TBCs, especially elastic moduli, should be evaluated ; what effect(s) the process variables have ; how high is the adhesion strength of ceramic top coat with Ni-based superalloys substrate and how it should be evaluated ; and how high is the residual stress in TBCs and how it should be evaluated. Elastic stiffness of air plasma sprayed (APSed) YSZ (; ZrO2 stabilized by 8 wt. pct. Y2O3) top coat specimen, which is frequently used for thermal barrier coating (TBC) system for advanced gas turbines, was measured by employing the macro-, micro-, and nano-indentation methods. The elastic stiffness was measured, following the Oliver-Pharr method. It was shown that the elastic stiffness of the YSZ, as well as the microstructure, were significantly influenced by the spraying conditions employed. Especially the size of ceramic powders used were found to have the most pronounced effect. It was also shown that the elastic stiffness revealed significant size effect : that is, there were significant differences in elastic stiffness between the macro-, micro-, and nano-indentation methods. The above size effect was discussed, correlating with some relating phenomena during the indentation process : crackings, sink-in, pile-up and spalling ; as well as with the characteristic microstructures of the sprayed top coat. Based on these knowledge, special discussions have been made on which type of microstructure should be controlled to develop high performance TBCs and how it can be realized through a control of spraying process variables.