The influence of cobalt,tantalum, and tungsten on the elevated temperature mechanical properties of single crystal nickel-base superalloys |
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Authors: | M V Nathal L J Ebert |
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Affiliation: | (1) NASA Lewis Research Center, 44135 Cleveland, OH;(2) Case Western Reserve University, 44106 Cleveland, OH |
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Abstract: | The influence of composition on the tensile and creep strength of 001] oriented nickel-base superalloy single crystals at
temperatures near 1000 °C was investigated. Cobalt, tantalum, and tungsten concentrations were varied according to a matrix
of compositions based on the single crystal version of MAR-M247.* For alloys with the baseline refractory metal level of 3
wt pct Ta and 10 wt pct W, decreases in Co level from 10 to 0 wt pct resulted in increased tensile and creep strength. Substitution
of 2 wt pct W for 3 wt pct Ta resulted in decreased creep life at high stresses, but improved life at low stresses. Substitution
of Ni for Ta caused large reductions in tensile strength and creep resistance, and corresponding increases in ductility. For
these alloys with low Ta plus W totals, strength was independent of Co level. The effects of composition on properties were
related to the microstructural features of the alloys. In general, high creep strength was associated with high levels ofγ′ volume fraction,γ-γ′ lattice mismatch, and solid solution hardening. |
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