Article

TEM investigation of intergranular stress corrosion cracking for 316 stainless steel in PWR environment

Department of Materials, Oxford University, Parks Road, Oxford, OX1 3PH, United Kingdom
Acta Materialia 01/2006; DOI: 10.1016/j.actamat.2005.10.011

ABSTRACT Type 316 stainless steel foils containing stress corrosion cracks grown in high temperature aqueous environments have been examined by transmission electron microscopy. It was found that the crack tips are oxidized and have a three-layered morphology where all the layers taper towards the crack tip. The inner layer is a microcrystalline spinel sandwiched between the outer layers of a nano-crystalline oxide. The outer layers are enriched in Cr, and the inner with Fe, relative to the matrix. Cu was observed to segregate at the interface between oxide and matrix at one crack in type 316 steel. The inner oxide growth is dominated by different mechanisms before and after the grain boundary cracks.

0 Bookmarks
 · 
155 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Nondestructive three-dimensional mapping of grain shape, crystallographic orientation, and grain boundary geometry by diffraction contrast tomography (DCT) provides opportunities for the study of the interaction between intergranular stress corrosion cracking and microstructure. A stress corrosion crack was grown through a volume of sensitized austenitic stainless steel mapped with DCT and observed in situ by synchrotron tomography. Several sensitization-resistant crack-bridging boundaries were identified, and although they have special geometric properties, they are not the twin variant boundaries usually maximized during grain boundary engineering.
    Science 07/2008; 321(5887):382-5. · 31.20 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The kinetics of corrosion of a low Cr-Mo steel alloy were studied over the temperature range of 75–250°C in 1 m NaCl in absence and in presence of various levels of contamination with CuCl2. Corrosion rates, weights of corrosion product (magnetite) film and total (integral) weight loss of the alloy over exposure times from 1 up to 480 h were measured. The corrosion rate decreases rapidly with time, before it levels off at longer time, indicating the formation of a protective corrosion product film. The ability of the alloy to retain an adherent corrosion product (magnetite) film was expressed in terms of a retention coefficient. This was found to increase with temperature and exposure time and to decrease with the level of contamination with CuCl2. This effect of temperature was attributed to the improvement of the crystallinity of the corrosion product. On the other hand, the effect of CuCl2 was attributed to the electrodeposition of Cu and its impregnation within the corrosion product, which becomes less adherent. The free corrosion potential was found to be affected by the presence of the CuCl2, in a fashion compatible with the Wagner-Traud theory of mixed potential.
    Materials and Corrosion 05/2007; 58(6):422 - 426. · 1.21 Impact Factor
  • Source
    Value in Health 01/2010; 13(7). · 2.19 Impact Factor

Full-text

View
4 Downloads
Available from