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The role of cobalt on the creep of WaspaloyCobalt was systematically replaced with nickel in Waspaloy (which normally contains 13% Co) to determine the effects of cobalt on the creep behavior of this alloy. Effects of cobalt were found to be minimal on tensile strengths and microstructure. The creep resistance and the stress rupture resistance determined in the range from 704 to 760 C (1300 to 1400 C) were found to decrease as cobalt was removed from the standard alloy at all stresses and temperatures. Roughly a ten-fold drop in rupture life and a corresponding increase in minimum creep rate were found under all test conditions. Both the apparent creep activation energy and the matrix contribution to creep resistance were found to increase with cobalt. These creep effects are attributed to cobalt lowering the stacking fault energy of the alloy matrix. The creep resistance loss due to the removal of cobalt is shown to be restored by slightly increasing the gamma' volume fraction. Results are compared to a previous study on Udimet 700, a higher strength, higher gamma' volume fraction alloy with similar phase chemistry, in which cobalt did not affect creep resistance. An explanation for this difference in behavior based on interparticle spacing and cross-slip is presented.
Document ID
19840011455
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Jarrett, R. N. (Columbia Univ. New York, NY, United States)
Chin, L. (Columbia Univ. New York, NY, United States)
Tien, J. K. (Columbia Univ. New York, NY, United States)
Date Acquired
September 4, 2013
Publication Date
February 1, 1984
Subject Category
Metallic Materials
Report/Patent Number
NASA-CR-174628
NAS 1.26:174628
Accession Number
84N19523
Funding Number(s)
CONTRACT_GRANT: NAG3-57
PROJECT: RTOP 505-33-1A
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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