Cyclic Thermal Shock Behaviors and Failure Mechanisms of Eb-Pvd Thermal Barrier Coating Under Radiant Heating

In this work, the cyclic thermal shock behaviors of the thermal barrier coating systems (TBCs) were investigated with the self-built thermal shock platform. The results showed that the cyclic thermal shock cycles significantly affected the microstructure and element distribution of TBCs. Firstly, the size of columnar gap in the top coating (TC) layer increases with the increase of the cyclic thermal shock cycles. And, the transverse micro-cracks generated near the tip of the columnar gap under the action of gradient stress. Moreover, Al elements in the bond coating (BC) significantly affected the growth mechanism of thermally grown oxide (TGO). Due to the consumption of Al element, the growth rate of the mixed oxide layer would be accelerated at the later stage of the experiment (the concentration of Al element in the BC layer dropped to a certain value). Finally, the accumulation of the thermal mismatch stress induced transverse cracks initiation and propagation in the porous mixed oxides layer. When the transverse crack was connected with the columnar gap, the TBCs would spall off at the interface of TC and TGO.