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Some TEM observations of Al2O3 scales formed on NiCrAl alloysThe microstructural development of Al2O3 scales on NiCrAl alloys has been examined by transmission electron microscopy. Voids have been observed within grains in scales formed on a pure NiCrAl alloy. Both voids and oxide grains grew measurably with oxidation time at 1100 C. The size and amount of porosity decreased towards the oxide-metal growth interface. It was postulated that the voids resulted from an excess number of oxygen vacancies near the oxide-metal interface. Short-circuit diffusion paths were discussed in reference to current growth stress models for oxide scales. Transient oxidations of pure, Y-doped, and Zr-doped NiCrAl was also examined. Oriented alpha-(Al,Cr)2O3 and Ni(Al,Cr)2O4 scales often coexisted in layered structures on all three alloys. Close-packed oxygen planes and directions in the corundum and spinel layers were parallel. The close relationships between oxide layers provided a gradual transition from initial transient scales to steady state Al2O3 growth.
Document ID
19800028901
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Smialek, J.
(NASA Lewis Research Center Cleveland, Ohio, United States)
Gibala, R.
(NASA Lewis Research Center; Case Western Reserve University Cleveland, Ohio, United States)
Date Acquired
August 10, 2013
Publication Date
July 1, 1979
Subject Category
Metallic Materials
Meeting Information
Meeting: Gordon Research Conference on Corrosion
Location: New London, NH
Start Date: July 23, 1979
End Date: July 27, 1979
Accession Number
80A13071
Distribution Limits
Public
Copyright
Other

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