Journal of Welding and Joining

The Korean Welding and Joining Society (대한용접접합학회)
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Effects of Post Weld Heat Treatment on Microstructures of Alloy 617 and 263 Welds for Turbines of HSC Power Plants

HSC발전소 터빈용 초내열합금 Alloy 617 및 263 용접부의 미세조직에 미치는 후열처리의 영향

  • Kim, Jeong Kil (Advanced Process Development Team, Doosan Heavy Industries & Construction) ;
  • Shim, Deog Nam (Advanced Process Development Team, Doosan Heavy Industries & Construction) ;
  • Park, Hae Ji (Advanced Process Development Team, Doosan Heavy Industries & Construction)
  • 김정길 (두산중공업 신공정기술개발팀) ;
  • 심덕남 (두산중공업 신공정기술개발팀) ;
  • 박해지 (두산중공업 신공정기술개발팀)
  • Received : 2016.02.03
  • Accepted : 2016.03.21
  • Published : 2016.06.30
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Abstract

Recently nickel based superalloys are extensively being regarded as the materials for the steam turbine parts for hyper super critical (HSC) power plants working at the temperature over $700^{\circ}C$, since the materials have excellent strength and corrosion resistance in high temperature. In this paper, alloy 617 of solution strengthened material and alloy 263 of ${\gamma}^{\prime}$-precipitation strengthened material were prepared as the testing materials for HSC plants each other. Post weld heat treatment (PWHT) was conducted with the gas tungsten arc (GTA) welded specimens. The microstructure of the base metals and weld metals were investigated with Electron Probe Micro-Analysis (EPMA) and Scanning Transmission Electron Microscope (STEM). The experimental results revealed that Ti-Mo carbides were formed in both of the base metals and segregation of Co and Mo in both of the weld metals before PWHT and PWHT leaded to precipitation of various carbides such as Mo carbides in the specimens. Furthermore, fine ${\gamma}^{\prime}$ particles, that were not precipitated in the specimens before PWHT, were observed in base metal as well as in the weld metal of alloy 263 after PWHT.

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