Research on damage behavior of thermal barrier coatings based on acoustic emission technology

Thermal barrier coatings (TBCs) is a typical brittle, heterogeneous, multilayer structure material. The heat-loading effect during service will lead to premature peeling failure of the coating. The main failure modes are cracking and interface spalling failure of ceramic coating. The failure of the TBCs is mainly caused by the initiation, propagation and connection of microcracks. In this study, acoustic emission technique (AE) combined with microscopic morphology are used to study the failure process of TBCs under tensile load, and fast Fourier transform (FFT) and wavelet transform are used to identify the crack damage mode of TBCs. The results show that the tensile failure process of the TBCs is that the crack firstly sprouts on the surface of the ceramic coating and then spreads to the interface of the ceramic coating/bond coating. After reaching the interface, the crack will grow and propagate along with the interface, eventually leading to ceramic coating is peeled off; The failure process of the TBCs is divided into four steps. Meanwhile, the spectrum analysis shows that the frequency component of the substrate is around .020 MHz, the frequency component of the surface crack is .20–.25 MHz, and the interface crack is .15–.20 MHz.