Korean Journal of Materials Research (한국재료학회지)

Materials Research Society of Korea (한국재료학회)
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Correlation of the Microstructural Degradation and Mechanical Properties of IN 738LC

IN 738LC 합금의 미세조직 열화와 물성의 상관성 연구

  • 유정훈 (창원대학교 재료공학과) ;
  • 주성욱 (창원대학교 재료공학과) ;
  • 신기삼 (창원대학교 재료공학과, 금속재료공학과) ;
  • 허성강 (창원대학교 재료공학과, 금속재료공학과) ;
  • 이재현 (창원대학교 재료공학과, 금속재료공학과) ;
  • 김의현 (한전 전력연구원 발전연구실) ;
  • 정진성 (한전 전력연구원 발전연구실) ;
  • 장성호 (한전 전력연구원 발전연구실) ;
  • 송기욱 (한전 전력연구원 발전연구실) ;
  • 하정수 (한전 전력연구원 발전연구실)
  • Published : 2004.01.01
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Abstract

IN 738LC, the major material for gas-turbine for power generation, was heat treated at $750^{\circ}C$, $850^{\circ}C$, $950^{\circ}C$ for 1000, 2000, and 4000 hrs and the microstructural evolution and mechanical properties were examined using optical microscope, XRD, SEM/EDS. The results showed ${\gamma}$', the main strengthening elements in this alloy, was about 300 nm in size and was about 56% by area fraction in as-cast samples. The area fraction of ${\gamma}$' peaked at 2000 hours at $750^{\circ}C$. The average diameter of the ${\gamma}$' which was about 300 nm at ascast specimen increased to about 1 $\mu\textrm{m}$ after heat treatment at $950^{\circ}C$ for 4000 hrs. Carbides were formed at dendrite, cell or grain boundaries which was ascribed to the segregation caused by solute redistribution during solidification. It was found that MC type carbides formed at low temperature, whereas carbides of $M_{23}$ /$C_{ 6}$/ type formed at higher temperature or at longer degradation. The hardness and impact energy decreased as the heat treatment temperature or time of retention increased, which was inaccrodance with the area fraction of ${\gamma}$'.

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