Ni基超合金Inconel^[○!R]706のクリープおよびクリープ疲労特性に及ぼす環境およびショットピーニングの影響

概要

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Fleet leader machines with non-shot-peened discs made of Inconel^[○!R]706 were experienced to have cracks in the first stage gas turbine wheels. These were inter-granular cracking and observed to be highly stressed locations with less potential for oxidation, which is thought to be quasi-brittle inter-granular cracking due to stress induced atmospheric oxygen penetration, so called, hold-time cracking. To recognize this phenomenon, creep and creep-fatigue tests with smooth and notched specimens were conducted at 600 and 650℃ in air and vacuum and confirmed the environmental effects on those lives and fracture modes. Temperature dependency of this phenomenon was also evaluated by the atmospheric creep tests and found it occurred relatively low temperature below 700℃. Effect of shot peening which was one of the countermeasures for this phenomenon was evaluated and confirmed to extend the creep-fatigue life.
2013-07-19