Degradation Mechanisms of APS and EB-PVD Thermal Barrier Coatings

Thermal barrier coatings (TBCs) are a crucial technology in thermal stability. Their use to achieve surface temperature reduction of the underlying superalloys surpasses all other achievements in the field of material technologies that have taken place in the last three decades. The technological advances in TBCs make them suitable for operation in the most demanding high-temperature environment of aircraft and industrial gas-turbine engines. The performance of these multi-layered and multi-material systems, tailored for high-temperature applications, is closely linked to their microstructure evolution. Many factors influence the durability of TBCs; therefore, in order to tailor these engineering materials for high-temperature applications, it is required to have a comprehensive understanding of the effects of the contributing factors and their interaction with the development of advanced TBCs. Improvements in TBCs will require a better understanding of the complex changes in their structure and properties that occur under operating conditions that lead to their failure. This article overviews the intrinsic and extrinsic degradation mechanisms, including TGO growth, thermal shock, CMAS attack, hot corrosion, erosion, sintering and phase transformations, thermal fatigue, thermo-mechanical tensile and foreign object damage.