| Abstract: |
Surface engineering plays the essential role in enhancing the performance of high pressure turbine components which work under the most severe conditions of temperature and mechanical loading. Thermal Barrier Coating systems (TBC)s are economically demanded for efficient and environmental friendly gas turbine engines. In this study, an intermediate ±-Al2O3 layer was deposited by sol-gel on the raw surface of APS-CoNiCrAlY Bond Coat, which was deposited on superalloy substrate. The YSZ ceramic Top Coat was deposited on the top of Al2O3 layer by APS. The new TBC system was compared with the standard TBC system concerning the behavior under thermal cycling. The samples were investigated by optical microscopy, Scanning Electron Microscopy (SEM) equipped by Energy Dispersive X-ray analysis (EDX), X-ray Diffraction (XRD) and Raman spectroscopy. The crack length within the ceramic layer and the average thickness of Thermally Grown Oxide (TGO) layer were measured using image analysis software. It was found that the Al2O3 layer has the potential to reduce the crack length and TGO thickness by suppressing the formation of detrimental oxides. The Al2O3 layer acts as a barrier to diffusion of oxygen. This effect improves the behavior of metallic Bond Coat which usually suffers from oxidation, and hence increases the TBC life. The information generated from the study can be used to improve the performance of the TBC system under different operating conditions.
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