713C 合金のγ-γ′結線上にある一連の Ni 基耐熱合金(高温の組織と強度)(<特集>耐熱鋼・耐熱合金)

概要

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Nickel-base superalloys used for blades in gas turbines are strengthened by γ′(Ni_3Al solution-hardened by alloying elements) precipitates. A general tendency is observed that the alloy with the larger amount of γ′has the higher creep strength of the alloy, it is necessary to avoid the change in solid solution hardening of γ and γ′, i. e. to keep their compositions constant. So, a series of alloys whose compositions are on γ-γ′tie line of alloy Inconel 713C have been designed, The alloys were cast in vacuum to size to make creep rupture test pieces. Good agreement was obtained between the designed and measured amounts of γ′after aging at 1000℃. γ and γ′compositions were also nearly constant except Cr concentration which only a little affects γ and γ′strengths. The following three points became clear by creep rupture test. 1) The γ′precipitation hardeninig nickel-base superalloys have the maximum creep strength at about 65 mol%γ′. 2) If γ′amount is excess, eutectic γ′forms to reduce creep strength. 3) Grain boundary morphologies have effects on the rupture life.
1979-06-01