Mechanisms controlling the performance and durability of thermal barrier coatings

Thermal protection systems based on thermal barrier coatings are widely use d in turbine engines for propulsion and power generation. The benefit of th ese coatings resides in their ability to inhibit degradation of the underly ing structural superalloy component by thermo-mechanical fatigue and oxidat ion. Existing commercial coatings are well-engineered with established dura bility and cost benefits. However, they lose adhesion and spall from the un derlying metal with cyclic thermal exposure. Because of varied manufacturin g approaches and operating scenarios, several specific mechanisms are invol ved. Ultimately, failure is connected to the large residual compression in the thermally grown oxide and its interaction with imperfections at the coa ting/substrate interface. This interaction induces an energy release rate a t cracks emanating from the imperfections that eventually leads to buckling and spalling of the TBC. Recent work to understand these phenomena has hig hlighted several nuances and challenges. This paper provides an overview of the current understanding of factors affecting coating durability and pres ents relationships between the durability, the governing material propertie s and the salient morphological features.