Creep and stress rupture of a mechanically alloyed oxide dispersion and precipitation strengthened nickel-base superalloy |
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Authors: | T E Howson D A Mervyn J K Tien |
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Affiliation: | (1) Henry Krumb School of Mines, Columbia University, 10027 New York, NY;(2) Westinghouse Hanford Company, Richland, WA |
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Abstract: | The creep and stress rupture behavior of a mechanically alloyed oxide dispersion strengthened (ODS) and γ′ precipitation strengthened
nickel-base alloy (alloy MA 6000E) was studied at intermediate and elevated temperatures. At 760 °C, MA 6000E exhibits the
high creep strength characteristic of nickel-base superalloys and at 1093 °C the creep strength is superior to other ODS nickel-base
alloys. The stress dependence of the creep rate is very sharp at both test temperatures and the apparent creep activation
energy measured around 760 °C is high, much larger in magnitude than the self-diffusion energy. Stress rupture in this large
grain size material is transgranular and crystallographic cracking is observed. The rupture ductility is dependent on creep
strain rate, but usually is low. These and accompanying microstructural results are discussed with respect to other ODS alloys
and superalloys and the creep behavior is rationalized by invoking a recently-developed resisting stress model of creep in
materials strengthened by second phase particles. The analysis indicates that at the intermediate temperature the creep strength
is controlled by the high volume fraction of γ′ precipitates and the contribution to the creep strength from the oxide dispersion
is small. At the elevated temperature, the creep strength is derived mainly from the inert oxide dispersoids.
Formerly at Columbia University. |
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