Oxidation damage of APS thermal barrier coatings under high temperature

Thermal barrier coatings (TBCs) have received increased attention for advanced gas turbine engine application. The oxidation damage plays an important role of the failure under high temperature load. An Y2O3 partially stabilized ZrO2 ceramic top coating was deposited a NiCrAlY bond coating by air plasma spray (APS). The substrate was directionally solidified superalloy (DZ40M). Isothermal oxidation has been performed at 700 degrees C and 1050 degrees C for 100h. The oxidation results in three transformations of the weight, the interface and the surface characters. All the specimens were characterized by highly precision balance, scanning electron microscopy (SEM) in cross-section, microscope with MFK2 visual measurement system on its surface. The curve of oxidation kinetics is obtained by weighting those specimens. The weight gain of the specimen under 700 degrees C is close to zero. Under 1050 degrees C the weight gain is very distinct. On the other hand, the interface cracks occur and extend at the interface between the ceramic and bond coating by SEM method. The thermal growth oxide (TGO) gradually appears on the coating surface under high temperature oxidation by MFK2. Last but not least, those observations will provide some ideas and damage parameters for the non-destructive inspection (NDI) for TBC under thermal load.