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

Department of Materials, University of Oxford, Oxford, England, United Kingdom
Acta Materialia (Impact Factor: 4.47). 02/2006; 54(3):635-641. DOI: 10.1016/j.actamat.2005.10.011


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.

Full-text preview

Available from:
  • Source
    • "Type 316L stainless steel (SS) is a corrosion resistant alloy because of its tendency to form a protective oxide film, for which a great of data exists [1] [2] [3]. However, certain corrosion degradations, such as stress corrosion cracking (SCC) [4] [5] [6] [7] [8], have been observed on this material when it was used in nuclear power systems. The oxide films formed on stainless steels in the primary circle of steam generators and nuclear reactors are supposed to play a significant role in the process of SCC [9] [10] [11]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The passivity of 316L stainless steel in borate buffer solution has been investigated by Mott–Schottky, atomic absorption spectrometry (AAS) and X-ray photoelectron spectroscopy (XPS). The results indicate that the polarization curve in the passive region possesses several turning potentials (0 VSCE, 0.2 VSCE, 0.4 VSCE, 0.6 VSCE and 0.85 VSCE). The passive films formed at turning potentials perform different electrochemical and semiconductor properties. Further, the compositions of the passive films formed at turning potentials are investigated. The results reasonably explain why these potentials appear in the passive region and why specimens perform different properties at turning potentials.
    Full-text · Article · Nov 2010 · Corrosion Science
  • Source
    • "(a) are 0.3063nm (d220) and 0.4847nm (d111), which correspond to spinel [13]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Ultrasonic shot peening treatment is used to treat structural surfaces, which can enhance the overall strength, stiffness and fatigue life of the treated material. This process induces a layer of nanocrystal grains in the surface of austenitic stainless steel. The microstructure and the composition of the surface layer are examined using X-ray diffraction and transmission electron microscopy. Experimental results show that the grains are mainly composed of oxide nanocrystal particles, NiFe2O4, and a few martensite particles. Phase transformations happen during the course of the ultrasonic shot peening. The chemical composition of the nano-layer is (8.03 Cr, 4.32 Ni, 3.86 Cu, 83.79 Fe) (mass %).
    Preview · Article · Nov 2008 · Proceedings of SPIE - The International Society for Optical Engineering
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The electrochemical behavior of a low alloy steel (Fe-2.25 Cr-1Mo) was investigated in 1 m NaCl over a range of temperatures (75-2500C) with various levels of contaminations with CuCl2. The change in free corrosion potential with time and the anodic and cathodic potentiodynamic polarization were measured. Cyclic potentiodynamic polarization was also measured on a previously corroded electrodes for different times (7 and 72 hrs) either in the same or in a fresh electrolyte. The results revealed that the corrosion potential is shifted, at all temperatures, towards more noble values to an extent which increases with the concentration of CuCl2. The cathodic current density also increases as the concentration of CuCl2 increases. CuCl2 acts as cathodic depolarizer. It undergoes electrodeposition leading to the formation of Cu metal onto the corrosion product, which becomes less adherent and less protective. Most of this Cu metal falls off the alloy surface along with the spalled corrosion product. The shift in the corrosion potential towards more noble values with the increase in the precorrosion time, in absence of Cu2+ ions, indicates that the corrosion product which forms protect the surface against further attack. In the presence of Cu2+ ions, the passivation occurred after the effect of copper is diminished.
    Full-text · Article · Jan 2006
Show more