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The substitution of nickel for cobalt in hot isostatically pressed powder metallurgy UDIMET 700 alloysNickel was substituted in various proportions for cobalt in a series of five hot-isostatically-pressed powder metallurgy alloys based on the UDIMET 700 composition. These alloys were given 5-step heat treatments appropriate for use in turbine engine disks. The resultant microstructures displayed three distinct sizes of gamma-prime particles in a gamma matrix. The higher cobalt-content alloys contained larger amounts of the finest gamma-prime particles, and had the lowest gamma-gamma-prime lattice mismatch. While all alloys had approximately the same tensile properties at 25 and 650 gamma C, the rupture lives at 650 and 760 C peaked in the alloys with cobalt contents between 12.7 and 4.3 pct. Minimum creep rates increased as cobalt contents were lowered, suggesting their correlation with the gamma-prime particle size distribution and the gamma-gamma-prime mismatch. It was also found that, on overaging at temperatures higher than suitable for turbine disk use, the high cobalt-content alloys were prone to sigma phase formation.
Document ID
19850055264
Document Type
Reprint (Version printed in journal)
Authors
Harf, F. H. (NASA Lewis Research Center Cleveland, OH, United States)
Date Acquired
August 12, 2013
Publication Date
June 1, 1985
Publication Information
Publication: Metallurgical Transactions A - Physical Metallurgy and Materials Science
Volume: 16A
ISSN: 0360-2133
Subject Category
METALLIC MATERIALS
Distribution Limits
Public
Copyright
Other