Over temperature in thermal barrier coating system induced by local spallation of ceramic layer

The capability to maintain operational temperature in safe limit is pivotal for the durability of thermal barrier coating system (TBCs). However, the spallation of TBCs during service may cause local over temperature in TBCs, thereby leading to the catastrophic failure. In this work, we investigate the over temperature in locally spalled TBCs through a combination of numerical calculation and experiment. We numerically calculate the temperature fields in locally spalled TBCs of different spallation depths and spallation diameters, and study the relationship between the maximum temperature in the spalled TBCs and the spallation size. Subsequently, we experimentally study the local spallation induced over temperature in TBCs, and validate by the relationship between the maximum temperature and the spallation size. We assess the effects of gas temperature (1700 K ∼ 1800 K), spallation depth (0.2 mm ∼ 0.6 mm), and spallation diameter (0 ∼ 20 mm) on the maximum temperature in locally spalled TBCs. Furthermore, we identify a critical spallation size of TBCs, beyond which over temperature occurs. The results show that the spallation size of TBCs is vitally important to the thermal management of gas turbine.