Residual stress evolution regularity in thermal barrier ceramic coatings （TBCs） under different cycles of thermal shock loading of 1 100℃ was investi- gated by the microscopic digital image correlation （DIC） and micro-Raman spec- troscopy, respectively. The obtained results showed that, as the cycle number of the thermal shock loading increases, the evolution of the residual stress under- goes three distinct stages： a sharp increase, a gradual change, and a reduction. The extension stress near the TBC surface is fast transformed to compressive one through just one thermal cycle. After different thermal shock cycles with peak temperature of 1 100℃, phase transformation in TBC does not happen, whereas the generation, development, evolution of the thermally grown oxide （TGO） layer and micro-cracks are the main reasons causing the evolution regularity of the residual stress.
Residual stress measurement is of critical significance to in-service security and the reliability of engineering components, and has been an active area of scientific interest. This paper offers a review o[ several prominent mechanical release methods for residual stress measurement and recent developments, focusing on the hole-drilling method combined with advanced optical sensing. Some promising trends for mechanical release methods are also analyzed.
The insulation effect of ceramic coating in a turbine blade is of great importance for the service of engine in the field of aviation industry. Fabricating microstructure in the thermal barrier coatings(TBCs) is considered to be able to enhance the thermal insulation effect. In this study, the traditional three-layer structure, containing ceramic top coat, bonding coat and substrate, is firstly simplified into a double-layer structure, where only ceramic layer and substrate are left, for analyzing the thermal insulation. Afterwards, the thermal insulation effect of the designed microstructure in the bonding coat of the three-layer structure is further studied. Column-like microstructures, filled with hollow ceramic microspheres in the interspace, are designed to improve the thermal insulation effect. The size parameters of the designed microstructure were optimized. The existence of the designed microstructure can significantly prolong the efficiency of thermal barrier coatings. The insulation temperature between the heating surface and lower surface of the substrate can exceed 300℃ and the thermal balance time has a big improvement of 240 s, more than 50%, than the traditional TBCs structure. Compared with the TBCs structure without microstructure, the designed microstructure can significantly improve the insulation temperature of more than 110℃.
Yanyan YinRui QiHongye ZhangShangbin XiYingbin ZhuZhanwei Liu
