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| Home > Publications database > Alumina Formation and Microstructural Changes of Aluminized CoNiCrAlY Coating During High Temperature Exposure in the Temperature Range 925–1075°C |
| Home > Publications database > Alumina Formation and Microstructural Changes of Aluminized CoNiCrAlY Coating During High Temperature Exposure in the Temperature Range 925–1075°C |
| Journal Article | FZJ-2018-07269 |
; ; ; ;
2018
Elsevier Science
Amsterdam [u.a.]
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Please use a persistent id in citations: doi:10.1080/09603409.2017.1392114
Abstract: MCrAlY (M = Ni, Co) coatings are commonly used on gas-turbine components as oxidation resistant overlay coatings and bondcoats for thermal barrier systems. In the present work the microstructural features and oxidation behavior of an aluminized Co-base MCrAlY-coating on a Ni-based superalloy have been investigated in the temperature range 925–1075 °C. Microstructural studies of the oxidized coatings by SEM/EBSD were complemented with numerical thermodynamic calculations using the software package ThermoCalc. In the as-received condition the outer part of the coating consisted mostly of β-(Ni,Co)Al. Formation of σ-CoCr was observed at the interface between the β-layer and the inner initial CoNiCrAlY. During high-temperature air exposure alumina based surface scales were formed but the oxidation induced Al depletion of the aluminized coating did not result in formation of the γ’-(Ni3Al) phase. Rather, the subscale formation of Co/Cr-rich phases was observed and a direct transformation of β- into γ-Ni phase after longer times. It is expected that these subscale microstructural changes thus affect the alumina formation and growth as well as the critical aluminum depletion in a different manner as in the case of corresponding β-NiAl coatings, although a direct comparison between various coating systems was not possible on the basis of the present results.
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