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Interfacial Composition Measurements in Complex Ni-Base Superalloys

Published online by Cambridge University Press:  10 February 2011

E. L. Hall  and
J. Bentley
E. L. Hall
Affiliation:
GE Corporate Research & Development, PO Box 8, Schenectady, NY 12301, [email protected]
J. Bentley
Affiliation:
Metals and Ceramics Division, Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831–6376
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Abstract

In this study, three different Ni-base superalloy / heat treatment combinations are studied in an attempt to assess the role of grain boundary morphology, composition, and phase distribution on mechanical properties, particularly time-dependent fatigue crack growth. The alloys chosen include one in which crack growth can be slowed by slow-cooling, and one in which crack growth is slow in the fast-cooled state. Both x-ray spectroscopy and energy-filtered imaging in the analytical electron microscope were used to measure grain boundary composition. The x-ray spectroscopy showed some enhancement of Cr, Mo, and W in the γ matrix at grain boundaries in the fast-cooled state, which was not present after slow cooling. Energy-filtered imaging showed no significant enhancement in alloying elements at interfaces in any of the samples studied. The results did show the tendency for the γ matrix to quickly equilibrate by second-phase precipitation, and a preference to avoid γ ‘- γ’ interfaces. The conclusions of this study are that time-dependent fatigue crack growth behavior in these alloys cannot be completely explained on the basis of grain boundary composition of major alloying elements.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 458: Symposium W – Interfacial Engineering for Optimized Properties , 1996 , 121
Copyright
Copyright © Materials Research Society 1997

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References

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