The Effect of Alloying Elements and Heat Treatment on the Pitting Corrosion of 440 A Martensitic Stainless Steels

440A 강의 공식부식에 미치는 첨가원소 및 열처리의 영향

  • Kim, Moo-Gil (Dept. of Metal System Engineering, Pukyong National University) ;
  • Jung, Byong-Ho (Dept. of Metal System Engineering, Pukyong National University) ;
  • Lee, Byoung-Chan (Dept. of Advanced Material, Ulsan Campus of Koreapolytechnic VII)
  • 김무길 (부경대학교 신소재공학부 금속시스템공학과) ;
  • 정병호 (부경대학교 신소재공학부 금속시스템공학과) ;
  • 이병찬 (한국폴리텍VII대학 울산캠퍼스 신소재응용학과)
  • Published : 2009.03.30

Abstract

440A martensitic stainless steels which were modified with reduced carbon content (${\sim}$0.5%) and addition of small amount of nickel, vanadium, tungsten and molybdenum were manufactured. Effects of alloying elements and heat treatment on the pitting corrosion in 3.5% NaCl were investigated through the electrochemical polarization tests. The lowest pitting potential, $E_p$, was obtained when austenitizing temperature was $1250^{\circ}C$ and this is because of the grain coarsening. When austenitized at $1050^{\circ}C$ and tempered at $350{\sim}750^{\circ}C$, the highest $E_p$ was obtained at $350^{\circ}C$, while the lowest at $450^{\circ}C$ and $550^{\circ}C$ regardless of alloying elements added. But $E_p$ was increased a little at the tempering temperature of $450^{\circ}C$ and $550^{\circ}C$ when 0.4 wt.% of tungsten was added. More pitting was observed at $450{\sim}550^{\circ}C$, and pitting was formed at regions where Cr concentration is low or grain boundaries are intersecting and showed irregular shape.

Keywords

References

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