title: Examinations of oxidation and sulfidation of grain boundaries in alloy 600 exposed to simulated pressurized water reactor primary water.
abstract: High-resolution characterizations of intergranular attack in alloy 600 (Ni-17Cr-9Fe) exposed to 325°C simulated pressurized water reactor 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.
authors.affiliation: Pacific Northwest National Laboratory, Richland, WA 99352, USA. daniel.schreiber@pnnl.gov
authors.forename: D K
authors.initials: DK
authors.lastname: Schreiber
authors.forename: M J
authors.initials: MJ
authors.lastname: Olszta
authors.forename: D W
authors.initials: DW
authors.lastname: Saxey
authors.forename: K
authors.initials: K
authors.lastname: Kruska
authors.forename: K L
authors.initials: KL
authors.lastname: Moore
authors.forename: S
authors.initials: S
authors.lastname: Lozano-Perez
authors.forename: S M
authors.initials: SM
authors.lastname: Bruemmer