Simulation of 1500 °C Thermal Shock for Novel Structural Thermal/Environmental Barrier Coatings System

Abstract

In recent years, with the development of SiC composites in aero-engine hot-end components, environmental barrier coatings (EBCs) have received extensive attention. Moreover, in order to elevate the service temperature, it is a developing trend to apply thermal barrier coatings (TBCs) with low thermal conductivity on EBCs coating system to form thermal/environmental barrier coatings (T/EBCs). However, the combination of high coefficient of thermal expansion (CTE) of TBCs with low CTE of EBCs often leads to premature failure due to excessive thermal expansion mismatch stress. However, a novel structural thermal barrier coating with embedded micro-agglomerated particles (EMAP TBC) by using atmospheric plasma spraying (APS) process has brought hope to solve this problem due to its low elastic modulus. Therefore, in this study, an innovative EMAP Gd2Zr2O7 T/EBCs coating system (EMAP Gd2Zr2O7/Yb2Si2O7/Si) under 1500 °C flame thermal shock was simulated and systematically studied on the SiC substrate. The results showed that the EMAP Gd2Zr2O7 T/EBCs coating system has much lower thermal stress than the conventional Gd2Zr2O7/Yb2Si2O7/Si T/EBCs coating system. Furthermore, when the thickness of each layer of the EMAP Gd2Zr2O7 T/EBCs coating system varies, to meet the thermal insulation requirements of Yb2Si2O7 layer and reduce the thermal shock stress, the thickness of the EMAP Gd2Zr2O7 layer is recommend being about 100 μm. Meanwhile, the thicknesses of Yb2Si2O7 and Si layers can be set as large as needed. In addition, with the increase in Yb2SiO5 doping content in the Yb2Si2O7 intermediate layer, the EMAP Gd2Zr2O7 T/EBCs coating system suffers a greater risk of spalling failure due to the increase in thermal stress.