• Title/Summary/Keyword: Austenitic 304 Sainless Steel

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Microstructure and Corrosion Characteristics of Austenitic 304 Stainless Steel Subjected to Long-term Aging Heat Treatment (장시간 시효 열처리된 오스테나이트계 304강의 미세조직과 부식 특성)

  • Huh, ChaeEul;Kim, ChungSeok
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.21 no.1
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    • pp.56-65
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    • 2022
  • The electrochemical corrosion properties of austenitic AISI 304 steel subjected to a long-term-aging heat treatment were investigated. AISI 304 steel was aged at 700 ℃ for up to 10,000 h. The variation in the microstructure of the aged specimens was observed by optical microscopy and scanning electron microscopy. Electrochemical polarization experiments were performed to obtain the corrosion current density (Icorr) and corrosion potential (Ecorr). Analyses indicated that the metastable intermetallic carbide M23C6 formed near the γ/γ grain boundary and coarsened with increasing aging time; meanwhile, the δ-ferrite decomposed into the σ phase and into M23C6 carbide. As the aging time increased, the current density increased, but the corrosion potential of the austenitic specimen remained high (at least 0.04 ㎛/cm2). Because intergranular carbide was absent, the austenitic annealed specimen exhibited the highest pitting resistance. Consequently, the corrosion resistance of austenitic AISI 304 steel decreased as the aging heat treatment time increased.