Thermal stress analysis of optimized functionally graded coatings during crack propagation based on finite element simulation

Abstract

Thermal barrier coatings (TBCs) are widely used in aircraft engines to protect their superalloy turbine blades in high inlet-temperature environments. However, the mismatch of the thermal expansion between the ceramic top layer and the bonding layer causes thermal stresses during thermal cycling, which can lead to cracks and failure of the TBCs system. In this paper, three different structures of TBCs were analyzed, which were single ceramic layer coatings (SCLC), double ceramic layer coatings (DCLC), and optimized functionally graded coatings (OFGC). In this paper, the propagation of horizontal and longitudinal cracks in TBCs of different structures during thermal cycling was analyzed by finite element simulations. The axial and radial maximum stress values and minimum stress values at the crack tip during thermal cycling of TBCs were analyzed. The results indicated that the OFGC structure could effectively reduce the thermal stress at the crack tip of the coating system during thermal cycling. The introduction of a gradient structure could improve the lifetime and thermal shock resistance of the coating.