Thermal shock behaviors and failure mechanisms of EB-PVD thermal barrier coatings using radiant heating

Abstract

In this work, the thermal shock behaviors and failure mechanisms of the thermal barrier coatings (TBCs) were investigated with the self-built thermal shock platform. The results showed that the thermal shock cycles significantly could affect the microstructure and element distribution of TBCs. Firstly, the size of columnar gaps in the top coating (TC) layer increased with the increase of the thermal shock cycles. And, the transverse micro-cracks generated near the tip of the columnar gaps under the action of gradient stress. Moreover, Al elements in the bond coating (BC) significantly affected the growth mechanism of thermally grown oxide (TGO). The growth rate of the mixed oxide layer would be accelerated when 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, and the adhesion strength of TBCs decrease. When the transverse crack was connected with the columnar gaps, the TBCs would peeling off and failure at the interface of TC and TGO.