| 1. |
- Brodin, Håkan, 1969-, et al.
(author)
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Bond Coat Influence on TBC Life
- 2002
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In: Turbin Forum, Advanced Coatings for High Temperatures,2002.
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Conference paper (peer-reviewed)
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| 2. |
- Chen, Weimin, 1959-, et al.
(author)
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Nature and Formation of Non-Radiative Defects in GaNAs and InGaAsN
- 2002
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In: MRS Fall Meeting 2001,2001. - Materials Research Society Symposium - Proceedings, Vol. 692 : MRS. ; , s. 67-72
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Conference paper (peer-reviewed)abstract
- The optically detected magnetic resonance (ODMR) technique has been employed to examine the nature and formation mechanism of non-radiative defects in GaNAs and InGaAsN. In both alloys, two defects were observed and were shown to be deep-level, non-radiative recombination centers. One of the defects has been identified as a complex involving an AsGa antisite. These two defects gain more importance with increasing N composition up to 3%, presumably due to an increase in their concentration. With a further higher N composition, the defects start to lose importance in carrier recombination that is attributed to an increasingly important role of other new non-radiative channels introduced with a high N composition. On the other hand, effect of In composition up to 3% seems to be only marginal. Both defects were shown to be preferably introduced in the alloys during low-temperature growth by molecular beam epitaxy (MBE), but can be rather efficiently removed by post-growth rapid thermal annealing.
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| 3. |
- Li, Xin-Hai, et al.
(author)
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The use of acoustic emission technology in coating ductility testing at various temperatures
- 2004
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In: Proceedings of the ASME Turbo Expo 2004 [Volume 4: Turbo Expo 2004]. - : ASME. - 0791841693 ; , s. 753-761
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Conference paper (peer-reviewed)abstract
- In this study, tests of ductility and ductile to brittle transition temperature DBTT of both PtAl RT22 and MCrAlY Amdry 997 coatings on both single crystal and polycrystalline substrates (CMSX-4, SCB, and In792) have been carried out. An acoustic emission detection technique that makes the detection of coating failures (micro cracking and delamination) possible has been employed during the tensile tests. The acoustic emission AE detection has been calibrated on the uncoated substrates and on some coated specimens at various testing temperatures and at different strain rate, together with metallurgical examination. A correlation between AE signals and failure types is established. It has been found that the substrate materials generate also some AE signals during plastic deformation. The amplitude of the AE signals depends strongly on the type of substrate material and the testing temperature but slightly on the strain rate. The substrate emissions may disturb the detection of coating failure. However, except for the disturbance from the substrate materials, the AE is still a sensitive, reliable, and useful technique to detect coating failures at various temperatures. The ductility results determined in this study have shown that the overlay coating Amdry 997 has a lower DBTT ∼550°C and higher ductilities than the diffusion coating RT22. Both of these differences indicate that Amdry 997 is much more ductile than RT22.
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| 4. |
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| 5. |
- Tang, Jun Eu, 1974, et al.
(author)
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Microanalysis on the oxidation and sulfate attack of partially stabilized zirconia thermal barrier coating
- 2001
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In: Ceramic Engineering and Science Proceedings. - 0196-6219 .- 1940-6339. ; 22:4, s. 463-470
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Journal article (peer-reviewed)abstract
- This aim of this investigation is to study the effect of the presence of Na2SO4 deposits and water vapor on the oxidation of an air plasma-sprayed TBC composed of a partially stabilized ZrO2 top coat with an underlying NiCoCrAlY bond coat. XRD and SEM/EDX were used to analyze the changes in the coatings after oxidation at 1000degreesC for 72 hours in dry or humidified (containing 50% H2O) O-2 atmosphere, with or without Na2SO4 deposited on the top coat. When oxidized in oxygen, bond coat oxide regions, consisting of almost pure aluminum oxide, were formed at the top coat / bond coat and bond coat / substrate interfaces and in the bond coat around the splat lines. When water vapor was present, the top coat / bond coat interface oxide was marginally thicker and included small regions with more chromium, cobalt and nickel. The addition of the salt deposits resulted in some destabilization in the outermost regions of the top coat. The salt deposits also caused the formation of thicker oxide comprising two regions, though this formation was observed only at the top coat / bond coat interface. The first type was a thin inner (i.e. bordering the bond coat) oxide that was mostly aluminum oxide. The other was a much thicker oxide containing higher levels of chromium, cobalt and nickel along with aluminum. In this oxide region, the aluminum level was higher when the chromium level was lower and vice versa.
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