Failure Analysis of Thermal Barrier Coating on Aero Engine Floating Tile

The floating tiles of the flame tube of aero-engine are protected by plasma spraying Y₂O₃-ZrO₂ thermal barrier coating. After the engine test run, the thermal barrier coating fell off and failed in some areas of the floating tiles. The surface morphology, microstructure, micro-domain composition and phase composition of the floating tiles with coating peeling off were analyzed by stereo microscope, scanning electron microscope, energy dispersive spectrometer, and X-ray diffractometer. The results show that the Y₂O₃-ZrO₂ top coating is spalled and the NiCoCrAlY coating is remained. The cracks initiated near the thermally grown oxides that was formed by the unmelted particle protrusions of the NiCoCrAlY bottom layer, and propagated along the direction parallel to the interface. The reason for the detachment of ceramic surface layer was related the excessive amount of unmelted particles and pores in the thin metal bottom layer, and the presence of monoclinic m-phase in the ceramic surface layer. The excessive stress resulted in the ceramic surface layer cracking and peeling in at high temperatures. Strengthening the inspection of the microstructure of the coating and using the nanostructure agglomerated coating powder can improve the working reliability of the thermal barrier coating.