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High-Temperature Tensile Strengths of Alloy 617 Diffusion Weldment

Alloy 617 확산용접재의 고온 인장강도

  • 사인진 (한국원자력연구원 고온가스로개발부) ;
  • 황종배 (충남대학교 신소재공학과) ;
  • 김응선 (한국원자력연구원 고온가스로개발부)
  • Received : 2018.04.15
  • Accepted : 2018.06.18
  • Published : 2018.06.30

Abstract

A compact heat exchanger is one of critical components in a very high temperature gas-cooled reactor (VHTR). Alloy 617 (Ni-Cr-Co-Mo) is considered as one of leading candidates for this application due to its excellent thermal stability and strengths in anticipated operating conditions. On the basis of current ASME code requirements, sixty sheets of this alloy are prepared for diffusion welding, which is the key technology to have a reliable compact heat exchanger. Optical microscopic analysis show that there are no cracks, incomplete bond, and porosity at/near the interface of diffusion weldment, but Cr-rich carbides and Al-rich oxides are identified through high resolution electron microscopic analysis. In high-temperature tensile testing, superior yield strengths of the diffusion weldment compared to the code requirement are obtained up to 1223 K ($950^{\circ}C$). However, both tensile strength and ductility drop rapidly at higher temperature due to the insufficient grain boundary migration across the interface of diffusion weldment. Best fit curves for minimum yield strength and average tensile strength are drawn from the experimental tensile results of this study.

Keywords

References

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