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The effect of tantalum on the structure/properties of two polycrystalline nickel-base superalloys: B-1900 + Hf MAR-M247The microstructure, phase compositions, and phase fractions were studied in conventionally cast B-1900 + Hf and both conventionally cast and directionally solidified MAR-M247 as a function of tantalum concentration. The hot tensile and creep rupture properties of the solutionized and aged MAR-M247-type alloys were also determined as a function of tantalum level. The effects of tantalum on the microstructure and phase compositions of B-1900 + Hf and MAR-M247 (conventionally cast and directionally solidified) were found to be very similar. The addition of tantalum to the as cast and heat treated alloys was shown to cause the partial replacement of the Hf in the MC carbides by Ta, although the degree of replacement was decreased by the solutionizing and aging heat treatment. The gamma prime and minor phase fractions (primarily MC type carbides) both increased approximately linearly with tantalum concentration. The gamma prime phase compositions were relatively insensitive to tantalum variations with the exception of the tantalum and/or hafnium levels. Bulk tantalum additions increased the tantalum, chromium, and cobalt levels of the gamma phase in both alloy series. The increase in the concentrations of the latter two elements in the gamma phase was a result of the decrease in the gamma phase fraction with increasing bulk tantalum concentration and constant gamma/gamma prime partitioning ratio. Tantalum additions increased the yield stress and ultimate tensile strength of the directionally solidified MAR-M247 type alloys and had no significant effect on ductility.
Document ID
19850009818
Acquisition Source
Legacy CDMS
Document Type
Thesis/Dissertation
Authors
Janowski, G. M. (Michigan Technological Univ. Houghton, MI, United States)
Date Acquired
September 5, 2013
Publication Date
February 1, 1985
Subject Category
Metallic Materials
Report/Patent Number
NAS 1.26:174847
NASA-CR-174847
Accession Number
85N18127
Funding Number(s)
CONTRACT_GRANT: NAG3-216
PROJECT: RTOP 505-33-62
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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