A methodology for fabrication of highly pitting corrosion-resistant type 304 stainless steel by plasma carburizing and post-pickling treatment

Yu Sugawara, Waka Inoue, Izumi Muto, Nobuyoshi Hara

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)

Abstract

Low temperature plasma carburizing was performed to improve the pitting corrosion resistance of Type 304 stainless steel. The optimal composition of the plasma gas and post-treatment were then examined. Carburizing was carried out for 18 ks at 470C in H2-CH4, Ar-H2-CH4 or Ar-CH4 plasma, and carburized layers ca. 9 μm in thickness with an average ca. 1.3 mass% carbon concentration were obtained. However, it was found that Cr23C6 was precipitated in the carburized layer and intergranular corrosion occurred under anodic polarization in 0.1 M NaCl. The precipitation behavior of Cr23C6 differed according to the plasma gas composition: H2 gas was found to suppress the size of Cr23C6. No Cr23C6 was precipitated in the inner part of the carburized layer formed in the H2-CH4 plasma, and no stable pit was initiated on the inner parts of the carburized layer under anodic polarization in 0.1 M NaCl. Pickling treatment using HF-HNO3 was applied to remove the Cr-depleted zones in the outer part of the plasma carburized layer. The Type 304 stainless steel after the plasma carburizing in the H2-CH4 atmosphere and subsequent the HF-HNO3 pickling exhibited no pitting corrosion under anodic polarization even in 3 M NaCl at 25C.

Original languageEnglish
Pages (from-to)C411-C449
JournalJournal of the Electrochemical Society
Volume165
Issue number9
DOIs
Publication statusPublished - 2018

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