Strategies for improving the lifetime of air plasma sprayed thermal barrier coatings

Air plasma sprayed (APS) thermal barrier coatings (TBCs) with typical lamellar structures have been widely applied on the hot sections of gas-turbine engines to increase operating temperatures and improve engine efficiencies. The TBCs undergo degradation which causes premature failure of the coatings during service. Failure of the APS TBCs occurs along or near the topcoat/bond coat interface, manifested by edge delamination and buckling. Understanding the degradation behavior and failure mechanisms is essential for further extending the lifetime of TBCs. Failure mechanisms regarding the residual stress, growth of the thermally grown oxides, sintering, interfacial degradation, and calcium–magnesium–alumino-silicates (CMAS) attack are discussed in the present work. The recent development of the strategies to mitigate the deleterious impacts of the life-limiting mechanisms is reviewed. Finally, future directions and challenges for the advancement of the APS TBCs are outlined.