한국주조공학회지 (Journal of Korea Foundry Society)

  • 제40권4호
  • /
  • Pages.118-127
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  • 2020
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  • 1598-706X(pISSN)
  • /
  • 2288-8381(eISSN)
한국주조공학회 (Korea Foundry Society)
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다결정 니켈기 초내열 합금 CM247LC의 온도에 따른 인장특성 변화

The Effect of Temperature on Tensile Properties in Conventionally Cast Ni-based Superalloy CM247LC

  • 최백규 (재료연구소 고온재료연구센) ;
  • 김인수 (재료연구소 고온재료연구센) ;
  • 도정현 (재료연구소 고온재료연구센) ;
  • 정중은 (재료연구소 고온재료연구센) ;
  • 석우영 (재료연구소 고온재료연구센) ;
  • 이유화 (재료연구소 고온재료연구센)
  • Choi, Baig-Gyu (High Temperature Materials Center, Korea Institute of Materials Science) ;
  • Kim, In Soo (High Temperature Materials Center, Korea Institute of Materials Science) ;
  • Do, Jeonghyeon (High Temperature Materials Center, Korea Institute of Materials Science) ;
  • Jung, Joong Eun (High Temperature Materials Center, Korea Institute of Materials Science) ;
  • Seok, Woo-Young (High Temperature Materials Center, Korea Institute of Materials Science) ;
  • Lee, Yu-Hwa (High Temperature Materials Center, Korea Institute of Materials Science)
  • 투고 : 2020.05.28
  • 심사 : 2020.08.13
  • 발행 : 2020.08.31
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초록

Microstructural evolution during a heat treatment and high-temperature tensile properties have been investigated in conventionally cast CM247LC. In as-cast specimens, MC carbides with high amounts of Ta, Ti, Hf, and W were found to exist in the interdendritic regions, and γ' was observed in the form of cubes and octocubes prior to decomposition into cubes. In the heat-treated condition, some portion of eutectic γ-γ' remained, and uniform cubic γ' was observed in both interdendritic regions and dendrite core. Three types of carbides with different stoichiometries and compositions were found at the grain boundaries. MC carbides with high Hf contents were observed in the vicinity of eutectic γ-γ'. The highest tensile strength value was found at 750℃, whereas the greatest ductility appeared at 649℃. The effect of the temperature on the tensile properties was closely related to the dislocation structure. With increase in the test temperature, the density of dislocations inside γ' decreased, whereas that in the γ matrix increased. Stacking faults generated in γ' at 750℃ had a strengthening effect, whereas thermally activated dislocation motion at a high temperature was considered to have the opposite effect.

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