Effect of Microstructural Bands on the Localized Corrosion of Laser Surface-Melted 316L Stainless Steel

Yoon Hwa, Christopher S. Kumai, Nancy Yang, Joshua K. Yee, Thomas M. Devine

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

The localized corrosion of laser surface melted (LSM) 316L stainless steel is investigated by a combination of potentiodynamic anodic polarization in 0.1 M HCl and microscopic investigation of the initiation and propagation of localized corrosion. The pitting potential of LSM 316L is significantly lower than the pitting potential of wrought 316L. The LSM microstructure is highly banded as a consequence of the high laser power density and high linear energy density. The bands are composed of zones of changing modes of solidification, cycling between very narrow regions of primary austenite solidification and very wide regions of primary ferrite solidification. Pits initiate in the outer edge of each band where the mode of solidification is primary austenite plane front solidification and primary austenite cellular solidification. The primary austenite regions have low chromium concentration (and possibly low molybdenum concentration), which explains their susceptibility to pitting corrosion. The ferrite is enriched in chromium, which explains the absence of pitting in the primary ferrite regions. The presence of the low chromium regions of primary austenite solidification explains the lower pitting resistance of LSM 316L relative to wrought 316L. The influence of banding on localized corrosion is applicable to other rapidly solidified processes such as additive manufacturing.

Original languageEnglish (US)
Pages (from-to)1014-1024
Number of pages11
JournalCorrosion
Volume77
Issue number9
DOIs
StatePublished - Sep 2021

Keywords

  • corrosion
  • laser additive manufacturing
  • microstructural bands
  • stainless steel

ASJC Scopus subject areas

  • General Chemistry
  • General Chemical Engineering
  • General Materials Science

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