Failure Of Thermal Barrier Coating High Temperature Oxidation And Thermal Shock

As one of advanced high-temperature protective coating techniques for working on the hot-section components, thermal barrier coatings (TBCs) can not only increase working temperature, but also improve service life of the components. In the future TBCs have promising attractive applications and researches in energy,ships , aviation and spacelight. So it is very important to study the failure mechanism of the thermal barrier coatings and the development of structure.In this paper, the thermal stress in the double layer thermal barrier coating specimens and the failure mechanism of the coating were analyzed.First, the plasma spraying method was used to manufacture a set of double layer thermal barrier specimens. Then, the oxidation test at high temperature and thermal shock experiment were performed with these specimens on the high temperature test machine. The samples were observed and the experimental results were analyzed. It was found that axial crack appeared on the cylindrical sample's TBCs under the thermal shock, this crack was caused by the circumferential stress; Spalling events in the disk sample was detected, this was caused by the high stress gradient in bond coat.Second, MARC as a finite element method(FEM)'s analyzed soft are used to establish a modal for some analytic simulation, and to investigate temperature and stress distribution in the TBCs under the thermal shock. It was analyzed in detail when the middle coatings failed, such as biaxial stress and shearing stress, discussed their role in the course of the failure mechanism. Compared the stress distribution under external applied load with the stress distribution of free load, we can find the effect of the failure on the TBCs by tension stress and compression stress. At the same time the stress distribution was also compared with the different coatings thickness.Finally, we use a new non-destructive testing tool—Photoluminescence. thesamples that have be exposed to the experiment of high temperature oxidation or the experiment of thermal shock are analyzed by Photoluminescence, and calculated the residual stress by the different oxidized time and shocked number.