Thermal cycling failure of new LaMgAl11O19/YSZ double ceramic top coat thermal barrier coating systems

New LaMgAl11O19 (LaMA)/YSZ double ceramic top coat thermal barrier coatings (TBCs) with the potential application in advanced gas-turbines and diesel engines to realize improved efficiency and durability were prepared by plasma spraying, and their thermal cycling failure were investigated. The microstructure evolutions as well as the crystal chemistry characteristics of LaMA coating which seemed to have strong influences on the thermal cycling failure of LaMA and the new double ceramic top coat TBCs based on LaMA/YSZ system were studied. For double ceramic top coat TBC system, interface modification of LaMA/YSZ by preparing thin composite coatings seemed to be more preferred due to the formations of multiple cracks during thermal cycling making the TBC to be more strain tolerant and as well as resulting in an improved thermal cycling property. The effects of the TGO stresses on the failure behavior of the TBCs were discussed through fluorescence piezo-spectroscopy analysis.

Research highlights
► The failure of LaMgAl11O19/YSZ double layered TBCs was reported for the first time.
► The nanocrystallization phenomenon of the LaMA coating was put forward.
► Single layered TBC may exhibit a life close to the corresponding double layered TBCs.