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Examinations of Oxidation and Sulfidation of Grain Boundaries in Alloy 600 Exposed to Simulated Pressurized Water Reactor Primary Water

Journal Article · · Microscopy and Microanalysis
 [1];  [2];  [2];  [2];  [2];  [2];  [2]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Univ. of Oxford (United Kingdom)
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
High-resolution characterizations of intergranular attack in alloy 600 (Ni-17Cr-9Fe) exposed to 325 °C simulated pressurized water reactor (PWR) primary water have been conducted using a combination of scanning electron microscopy, NanoSIMS, analytical transmission electron microscopy and atom probe tomography. The intergranular attack exhibited a two-stage microstructure that consisted of continuous corrosion/oxidation to a depth of ~200 nm from the surface followed by discrete Cr-rich sulfides to a further depth of ~500 nm. The continuous oxidation region contained primarily nanocrystalline MO-structure oxide particles and ended at Ni-rich, Cr-depleted grain boundaries with spaced CrS precipitates. Three-dimensional characterization of the sulfidized region using site-specific atom probe tomography revealed extraordinary grain boundary composition changes, including total depletion of Cr across a several nm wide dealloyed zone as a result of grain boundary migration.
Research Organization:
Pacific Northwest National Laboratory (PNNL), Richland, WA (United States), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Organization:
USDOE
DOE Contract Number:
AC05-76RL01830
OSTI ID:
1083397
Report Number(s):
PNNL--21595; 47700; KC0202040
Journal Information:
Microscopy and Microanalysis, Journal Name: Microscopy and Microanalysis Journal Issue: 3 Vol. 19; ISSN 1431-9276
Publisher:
Microscopy Society of America (MSA)
Country of Publication:
United States
Language:
English