Abstract
The role of water vapor on thermal barrier coating (TBC) performance has been investigated for both Pt-modified aluminide and Pt-diffusion bond coatings by characterizing the alumina scale after exposures at 1150°C. For both types of bond coatings, the average oxide scale thickness formed in dry O2 at 1150°C was lower than that formed in wet air, especially for air+10%H2O. In all cases, the average thickness was higher beneath the yttria-stabilized zirconia (YSZ) top coat. Characterization of the alumina scale formed without a YSZ top coat showed differences in morphology and Hf- and Ta-rich oxide precipitates at the gas interface depending on the environment. With and without water vapor, the β-(Ni,Pt)Al coatings showed a martensitic structure with 10-50nm α-Cr(Re) precipitates. Alumina grain boundary segregation of Y and Hf from the superalloy substrate was easier to detect for the Pt-diffusion coatings.
| Original language | English |
|---|---|
| Pages (from-to) | 30-38 |
| Number of pages | 9 |
| Journal | Surface and Coatings Technology |
| Volume | 215 |
| DOIs | |
| State | Published - Jan 25 2013 |
Funding
The authors would like to thank G.W. Garner, T.M. Lowe, H. Longmire, T. Jordan and D.W. Coffey for assistance with the experimental work and B. Nagaraj at GE Aircraft Engine for providing the substrates and EB-PVD coatings. This research was supported by the U.S. Department of Energy , Office of Coal and Power R&D , Office of Fossil Energy , and ORNL's Shared Research Equipment (ShaRE) User Facility , which is sponsored by the Office of Basic Energy Sciences, U.S. Department of Energy.
Keywords
- Hf segregation
- Pt-diffusion coatings
- Water vapor
- α-AlO
- β-(Ni,Pt)Al coatings