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Alloy Phase Stability Requirements in Single Crystal Superalloys

Published online by Cambridge University Press:  28 February 2011

David N. Duhl
David N. Duhl*
Affiliation:
Pratt and Whitney, Mail Stop 114-41 400 Main Street, East Hartford, CT 06108
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Abstract

Alloy phase stability is a critical parameter in the design and implementation of nickel-base superalloys. To achieve the high temperature properties required of single crystal superalloys for application in gas turbine machinery, these alloys must have a stable gamma plus gamma prime microstructure for long periods of time at elevated temperatures. Significant deviation from this stable two phase microstructure, due to the precipitation of other phases, results in the loss of critical alloy properties which can have a deleterious impact on engine performance.

Empirical methods based on the electron vacancy concept, commonly employed to predict and prevent the formation of undesirable topologically close packed (TCP) phases such as sigma or mu in polycrystalline nickelbase superalloys, are also used with single crystal superalloys. These undesirable phases result in the loss of alloy properties primarily as a result of the depletion of refractory strengthening elements from the superalloy matrix. The consequence of the formation of undesirable TCP phases on alloy properties and subsequent single crystal component behavior is reviewed.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 186: Symposium I – Alloy Phase Stability and Design , 1990 , 389
Copyright
Copyright © Materials Research Society 1991

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