Abstract
The oxidation behavior of iridium-aluminum and iridium-hafnium intermetallics has been investigated in various oxygen pressures and at temperatutes between 1550 and 1800°C. The hafnium concentration necessary for the formation of a continuous external HfO2 scale is above 50 at.% hafnium. The aluminum concentration necessary for the formation of a continuous external Al2O3 scale is above 55 at. % aluminum, which is the aluminum-rich boundary of the IrAl intermetallic. Thus, it appears that the IrAl25 intermetallic necessary for the formation of a protective, external Al2O3 scale in the iridiumaluminum system. The activation energy for the growth of Al2O3 on iridiuim (60 at.%) aluminum intermetallic is in agreement with that determined pre viously for the NiAl intermetallic at lower temperatures. This suggests that similar process may control the Al2O3 scale growth on these two intermetallics.
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Lee, K.N., Worrell, W.L. The Oxidation of iridium-aluminum and iridium-hafnium intermetallics at temperatures above 1550°C. Oxid Met 32, 357–369 (1989). https://doi.org/10.1007/BF00665443
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DOI: https://doi.org/10.1007/BF00665443