Coupling effect of microstructure and hydrogen absorbed during service on pitting corrosion of 321 austenitic stainless steel weld joints. (March 2020)

• Record Type: Journal Article
• Authors: Cao, Ruohan; Xu, Lining; Jiang, Baolong; Gao, Mengjie; Qu, Dingrong; Shan, Guangbin; Xu, Shujian; Qiao, Lijie
• Is Part Of: Corrosion science. Volume 164(2020)
• Publication Date: 2020-03
• Subjects: Stainless steel -- AFM -- SIMS -- Polarization -- Pitting corrosion; Corrosion and anti-corrosives -- Periodicals; 620.11223
• DOI: 10.1016/j.corsci.2019.108339
• Languages: English
• ISSNs: 0010-938X

Abstract

Graphical abstract: (a) Optical morphology of fusion line for ToF-SIMS test, (b) corresponding negative ions ToF-SIMS mapping of red box in (a) after 10 min of sputtering, and (c) SEM high magnification images of pits on fusion line after the immersion test. Highlights: Austenitic stainless steel weld joints served in a hydrocracking unit for 6 years Hydrogen segregation occurred at the ferrite/austenite phase boundaries Positions of the pit and hydrogen enrichment were microscopically consistent Hydrogen enrichment conditions varied under different microstructures, which induced the difference in pitting susceptibility Abstract: Pitting corrosion of austenitic stainless steel weld joints served in a hydrocracking unit for 6 years was examined. The microstructure of weld metal (WM) and fusion line (FL) was austenite and ferrite. After the immersion test, many pits were observed on the FL, whereas few pits were observed on the heat-affected zone (HAZ). Pits were microscopically initiated at ferrite/austenite boundaries. Hydrogen concentrations at FL and WM were higher than those of HAZ, and hydrogen segregation occurred at ferrite/austenite boundaries, which was consistent with the pit position. Hydrogen enrichment conditions varied under different microstructures, which induced the difference in pitting susceptibility.