Transactions of the Korean Society of Mechanical Engineers A (대한기계학회논문집A)

The Korean Society of Mechanical Engineers (대한기계학회)
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Evaluation of High-Temperature Tensile Property of Diffusion Bond of Austenitic Alloys for S-CO2 Cycle Heat Exchangers

고온 S-CO2 사이클 열교환기용 스테인리스강 및 Fe-Cr-Ni 합금 확산 접합부의 고온 인장 특성평가

  • Hong, Sunghoon (Dept. of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology) ;
  • Sah, Injin (Dept. of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology) ;
  • Jang, Changheui (Dept. of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology)
  • 홍성훈 (한국과학기술원 원자력 및 양자공학과) ;
  • 사인진 (한국과학기술원 원자력 및 양자공학과) ;
  • 장창희 (한국과학기술원 원자력 및 양자공학과)
  • Received : 2014.03.17
  • Accepted : 2014.05.28
  • Published : 2014.12.01
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Abstract

To improve the inherent safety of the sodium-cooled fast reactor (SFR), the supercritical $CO_2$ ($S-CO_2$) Brayton cycle is being considered as an alternative power conversion system to steam the Rankine cycle. In the $S-CO_2$ system, a PCHE (printed circuit heat exchanger) is being considered. In this type of heat exchangers, diffusion bonding is used for joining the thin plates. In this study, the diffusion bonding characteristics of various austenitic alloys were evaluated. The tensile properties were measured at temperatures starting from the room temperature up to $650^{\circ}C$. For the 316H and 347H types of stainless steel, the tensile ductility was well maintained up to $550^{\circ}C$. However, the Incoloy 800HT showed lower strength and ductility at all temperatures. The microstructure near the bond line was examined to understand the reason for the loss of ductility at high temperatures.

소듐냉각고속로(Sodium-cooled Fast Reactor, SFR)의 안전성 향상을 위해 고온 증기 Rankine 싸이클 대신 초임계 이산화탄소(Supercritical $CO_2$, $S-CO_2$) Brayton 싸이클을 전력변환 시스템에 사용하는 방안이 제시되고 있다. 이 경우, 중간 열교환기로는 확산 접합(Diffusion Bonding)에 의해 제작되는 미소채널형 열교환기인 PCHE(Printed Circuit Heat Exchanger)가 고려되고 있다. 따라서 본 연구에서는 PCHE 형 열교환기 후보재료인 다양한 오스테나이트계 합금의 확산접합 특성을 평가하였다. 후보재료별로 다양한 조건에서 확산접합부를 제작하고 상온에서 $650^{\circ}C$까지의 인장 특성을 평가하였다. 평가 결과 SS 316H와 SS 347H는 $550^{\circ}C$까지 모재와 유사한 특성을 보였지만 Fe-Ni-Cr 합금인 Incoloy 800HT는 모든 온도에서 인장특성이 감소하였다. 연신율 저하의 원인을 이해하기 위해 접합부 부근의 미세조직을 분석하였다.

Keywords

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