Thermal shock behavior of ZrO2-8%Y2O3coating on aluminized superalloy In-738LC

Thermal shock behaviour of thermal sprayed ZrO2-8%Y2O3 coating on aluminized superalloy In-738LC has been investigated. Thermal shock experiments consisted of rapid thermal cycling between 1100 ºC and 300 ºC. Visual observations were conducted after each cycle in order to identify macroscopic features such as macrocraking and spallation. Coating characterization before and after the thermal cycling was conducted by means of optical and scanning electron microscopes as well as EDS analysis. The results demonstrated that the coating response to the thermal cycling was consisted of TGO thickening، extending of the interdiffusion zone and transformation of β-NiAlγ''-Ni3Al in the aluminide coating. In addition، failure of the coating system comprised of pitting oxidation at aluminide topcoat، nucleation of cracks in TGO، and finally cracks propagation into the ceramic layer.