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Oxidation of Single-Crystal γ′-Ni3A1 at Low Oxygen Partial Pressure

Published online by Cambridge University Press:  26 February 2011

E. Schumann ,
G. Schnotz ,
U. Salzberger  and
M. Rühle
E. Schumann
Affiliation:
MPI für Metallforschung, Institut für Werkstoffwissenschaft, Seestrasse 92, D-7000 Stuttgart 1, Germany
G. Schnotz
Affiliation:
MPI für Metallforschung, Institut für Werkstoffwissenschaft, Seestrasse 92, D-7000 Stuttgart 1, Germany
U. Salzberger
Affiliation:
MPI für Metallforschung, Institut für Werkstoffwissenschaft, Seestrasse 92, D-7000 Stuttgart 1, Germany
M. Rühle
Affiliation:
MPI für Metallforschung, Institut für Werkstoffwissenschaft, Seestrasse 92, D-7000 Stuttgart 1, Germany
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Abstract

Single crystals of γ′-Ni3Al((001)-oriented) were oxidized at 1223 K under an oxygen partial pressure of ∼4 ×10−19 atm for times ranging from 0.1 to 50 hours. Microstructural development of the oxide scale and subscale metal was studied by electron microscopy. A special technique permitted the reproducible and efficient preparation of TEM cross section specimens. Initially, a fine-grained γ-Al2O3 scale formed with a preferred orientation. Depletion of Al from the γ′-Ni3Al resultedin a Ni-Al solid solution zone between the oxide scale and the intermetallic. After 20 hours oxidation, a discontinuous α-A12O3 layer between the γ-A12O3 and the metal was observed. The α-A12O3 layer exhibited a much larger grain size than that of the γ-A12O3 and was continuous after 50 hours oxidation. Formation of the α-A12O3 layer correlated with a decreasing parabolic oxidation rate constant kp, as measured by thermogravimetric analysis (TGA).

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 213: Symposium Q – High-Temperature Ordered Intermetallic Alloys IV , 1990 , 951
Copyright
Copyright © Materials Research Society 1991

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References

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