Yutaka Koizumi1, Toshiharu Kobayashi1, Tadaharu Yokokawa1, Makoto Osawa1, Hiroshi Harada1, Takehisa Hino2 and Yomei Yoshioka2
1High Temperature Materials Group, Materials Engineering Laboratory, National Institute for Materials Science, Tsukuba 305-0047
The γ′ fraction dependence of the creep properties of the second generation single crystal (SC) Ni-base superalloy, TMS-82+, and their γ/γ′ tie-line alloys is presented. The γ′ fraction is varied between 0 and 100%. The γ and γ′ phases of the alloys are designed to have the same chemical composition so that γ′ fraction dependence can be assessed independently. The γ single-phase alloy is weaker than the γ′ single-phase alloy. The best creepproperty is obtained with the γ′ fraction between 60 and 70%, depending on the creepcondition. The optimum γ′ fraction decreases at higher temperature and lower stress. The SC alloys show larger γ′ fraction dependence compared with the conventionally cast polycrystalline alloys previously reported.
(Received December 4, 2002)
nickel-base superalloys, single crystal, γ phase, γ′ phase, creep, TMS-82+
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