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Abstract
Isothermal oxidation tests have been carried out on a thermal barrier coating (TBC) system consisting of a nickel-based superalloy, CoNiCrAlY bond coat applied by HVOF and yttria-stabilised zirconia (YSZ) top coat applied by EB-PVD. Bond coat microstructure, coating cracking and failure were characterised using high resolution scanning electron microscopy complemented with compositional analyses using energy dispersive X-ray spectrometry. A protective alumina layer formed during the deposition of the YSZ top coat and this grew with sub-parabolic kinetics during subsequent isothermal oxidation at temperatures in the range 950 to 1150 degrees C. After short exposures at 1050 degrees C and final cooling, small sub-critical cracks were found to exist within the YSZ but adjacent to bond coat protuberances. Their formation is related to the development of local tensile strains associated with the growth of an alumina layer (TGO) on the non-planar bond coat surface. However, for the specimens examined, these cracks did not propagate, in contrast to other TBC systems, and final spallation was always found to have occurred at the bond coat/TGO interface. This shows that the strain energy within the TGO layer made a significant contribution to the delamination process.
Original language | English |
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Pages (from-to) | 317-323 |
Number of pages | 7 |
Journal | Materials at High Temperatures |
Volume | 26 |
Issue number | 3 |
DOIs | |
Publication status | Published - 1 Sept 2009 |
Keywords
- thermal barrier coating
- bond coat oxidation
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Dive into the research topics of 'The effect of bond coat oxidation on the microstructure and endurance of a thermal barrier coating system'. Together they form a unique fingerprint.Projects
- 1 Finished
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Structural Metallic Systems For Advanced Gas Turbine Applications
Bowen, P., Chiu, Y. & Reed, R.
Engineering & Physical Science Research Council
1/10/09 → 30/09/14
Project: Research Councils