Korean Journal of Materials Research (한국재료학회지)

Materials Research Society of Korea (한국재료학회)
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Pit Corrosion of SS420 Stainless Steel by Grain Boundary Sensitization

스테인레스강 SS420의 입계예민화에 의한 피트 부식

  • Choe, Byung Hak (Department of Advanced Metal & Materials Science Engineering, Gangneung-Wonju National Univ.) ;
  • Lee, Bum Gyu (Department of Advanced Metal & Materials Science Engineering, Gangneung-Wonju National Univ.) ;
  • Jang, Hyeon Su (Department of Advanced Metal & Materials Science Engineering, Gangneung-Wonju National Univ.) ;
  • Park, Chan Sung (Forensic Engineering Dept., National Forensic Service) ;
  • Kim, Jin Pyo (Forensic Engineering Dept., National Forensic Service) ;
  • Park, Nam Gyu (Forensic Engineering Dept., National Forensic Service) ;
  • Kim, Cheong In (CRA Piping Korea) ;
  • Kim, Bo Mi (HMW Co., Ltd.)
  • 최병학 (강릉원주대학교 신소재금속공학과) ;
  • 이범규 (강릉원주대학교 신소재금속공학과) ;
  • 장현수 (강릉원주대학교 신소재금속공학과) ;
  • 박찬성 (국립과학수사연구원) ;
  • 김진표 (국립과학수사연구원) ;
  • 박남규 (국립과학수사연구원) ;
  • 김청인 (씨알에이파이핑코리아(주)) ;
  • 김보미 (한국멕케이용접(주))
  • Received : 2017.03.23
  • Accepted : 2017.07.31
  • Published : 2017.08.27
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Abstract

This study investigated the surface pit corrosion of SS420J2 stainless steel accompanied by intergranular crack. To reveal the causes of surface pits and cracks, OM, SEM, and TEM analyses of the microstructures of the utilized SS420J2 were performed, as was simulated heat treatment. The intergranular cracks were found to have been induced by a grain boundary carbide of $(Cr,Fe)_{23}C_6$, which was identified by SEM/EDS and TEM diffraction analyses. The mechanism of grain boundary sensitization occurred at the position of the carbide, followed by its occurrence at the Cr depleted zone. The grain boundary carbide of $(Cr,Fe)_{23}C_6$ type precipitated during air cooling condition after a $1038^{\circ}C$ solid solution treatment. The carbide precipitate formation also accelerated at the band structure formed by cold working. Therefore, using manufacturing processes of cooling and cold working, it is difficult to protect SS420J2 stainless steel against surface pit corrosion. Several counter plans to fight pit corrosion by sensitization were suggested, involving alloying and manufacturing processes.

Keywords

References

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