The cross-sectional area elements scanning results of the nanostructured TBC after thermal shock testing at 1 150 and 1 250 ℃ are shown in Figs.1 and 2. It can be seen from Figs.1 and 2 that the diffusion of Al and O elements in the bond coat occurs. Al element diffuses from the bond coat toward the top coat/bond coat interface and O element diffuses through the top coat toward the bond coat and, as a result, Al2O3 formed at the interface. Inhomogeneous distributions of Al and O in the bond coat were observed from the area elements scanning pattern, indicating that Al2O3 also formed in the pore areas in the bond coat. Ni, Co, Cr and Ta are homogeneously distributed in the bond coat. The diffusions of Co, Cr, Al and Ta from the bond coat into the substrate are not evident when the temperature of thermal shock test is 1 250 ℃. Zr and Y in the ceramic top coat are stable.
Fig.1 SEM micrograph and cross-sectional area scanning results of nanostructured TBC after thermal shock testing at 1 150 ℃
Fig.2 SEM micrograph and cross-sectional area scanning results of nanostructured TBC after thermal shock testing at 1 250 ℃
The cross-sectional area elements distribution of the conventional TBC after thermal shock testing at 1 250 ℃ is shown in Fig.3. Al distribution in the bond coat is inhomogeneous. It concentrates at the top coat/bond coat interface where TGO forms. The inhomogeneous distribution of Al in the bond coat indicates that Al2O3 formed in the pore areas. Al and Cr were found on the surface layer of the Ni substrate.
Fig.3 SEM micrograph and cross-sectional area scanning results of conventional TBC after thermal shock testing at 1 250 ℃
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