scholarly journals Micromechanical testing of oxidized grain boundaries in Nickel alloys from nuclear reactors

2013 ◽  
Vol 1519 ◽  
Author(s):  
Sergio Lozano-Perez ◽  
Helen Dugdale ◽  
David E J Armstrong ◽  
Takumi Terachi ◽  
Takuyo Yamada ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Nickel Alloys ◽  
Nuclear Reactors ◽  
Pressurized Water ◽  
Grain Boundary Plane ◽  
Initiation And Propagation ◽  
Primary Water ◽  
Water Reactors

ABSTRACTThe fracture behaviour of individual grain boundaries has been studied in order to understand the mechanisms controlling stress corrosion cracking in nuclear reactors. In particular, the role of oxidation in facilitating crack initiation and propagation has been reviewed. Nickel alloys from pressurized water reactors (PWRs) have been tested in simulated primary water conditions to induce grain boundary oxidation. Microcantilevers containing an oxidized grain boundary plane have been prepared and tested for fracture. The brittle nature of the oxide was demonstrated and the required stress to fracture measured.

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

2013 ◽  
Vol 19 (3) ◽  
pp. 676-687 ◽  
Author(s):  
D.K. Schreiber ◽  
M.J. Olszta ◽  
D.W. Saxey ◽  
K. Kruska ◽  
K.L. Moore ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Atom Probe Tomography ◽  
Atom Probe ◽  
Alloy 600 ◽  
Pressurized Water Reactor ◽  
Intergranular Attack ◽  
Pressurized Water ◽  
Primary Water

AbstractHigh-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.

Atom-probe tomography of surface oxides and oxidized grain boundaries in alloys from nuclear reactors

2013 ◽  
Vol 1514 ◽  
pp. 107-118 ◽  
Author(s):  
Karen Kruska ◽  
David W Saxey ◽  
Takumi Terachi ◽  
Takuyo Yamada ◽  
Peter Chou ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Atom Probe Tomography ◽  
Nuclear Reactors ◽  
Bulk Material ◽  
Chemical Characterization ◽  
Atom Probe ◽  
Aqueous Environment ◽  
Pressurized Water ◽  
Surface Oxides

ABSTRACTThe preparation of site-specific atom-probe tomography (APT) samples containing localized features has become possible with the use of focused ion beams (FIBs). This technique was used to achieve the analysis of surface oxides and oxidized grain boundaries in this paper. Transmission electron microscopy (TEM), providing microstructural and chemical characterization of the same features, has also been used, revealing crucial additional information.The study of grain boundary oxidation in stainless steels and nickel-based alloys is required in order to understand the mechanisms controlling stress corrosion cracking in nuclear reactors. Samples oxidized under simulated pressurized water reactor primary water conditions were used, and FIB lift-out TEM and APT specimens containing the same oxidized grain boundary were prepared and fully characterized. The results from both techniques were found fully consistent and complementary.Chromium-rich spinel oxides grew at the surface and into the bulk material, along grain boundaries. Nickel was rejected from the oxides and accumulated ahead of the oxidation front. Lithium, which was present in small quantities in the aqueous environment during oxidation, was incorporated in the oxide. All phases were accurately quantified and the effect of different experimental parameters were analysed.

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