Progress update on failure mechanisms of advanced thermal barrier coatings: A review

Thermal barrier coatings (TBCs) have proved to be a key technology in thermal stability and their use to achieve surface temperature reduction of the underlying super alloys surpass all other achievements in the field of material technologies that have taken place in last three decades. The technological advances in TBCs also make them suitable for wider engineering and defense applications. The performance of these multi-layered and multi-material systems, tailored for high temperature applications is closely linked to their microstructure evolution. The article presents a comprehensive review of various degradation mechanisms to which the TBC system is subjected during service life viz. hot corrosion, CMAS attack, oxidation, erosion, foreign object damage, sintering and phase transformations. Strategies to mitigate the adverse impact of the degradation mechanisms and the recent advances toward reduction in the thermal conductivity of TBCs have also been discussed. The emphasis of this review is on the relationship between the properties and the microstructure of TBCs for better understanding of their life limiting mechanisms to assist developments in advanced and novel TBCs for engineering applications.