Cracking of zirconium alloys at constant load with and without applied potentials
Cladding materials, namely Zircaloy-2 (Zr-2) and Zircaloy-4 (Zr-4), were tested for evaluation of their resistance to stress corrosion cracking (SCC), delayed hydride cracking (DHC), and localized corrosion (pitting and crevice) in neutral and acidic environments at ambient temperature and 90Ã‚Â°C. For SCC testing, constant load and slow-strain-rate techniques were used. Some SCC testing were also performed under controlled electrochemical potentials (Econt). The localized corrosion behavior was studied by cyclic potentiodynamic polarization technique. Metallurgical microstructures and fractography were analyzed by optical microscopy and scanning electron microscopy (SEM), respectively. The results obtained from this study indicate that no failures were observed under constant loading with smooth specimens. However, the notched specimens showed failures at reduced applied loads. The application of Econt to the smooth specimens showed some signs of hydrogen damage that might be the precursor to the development of DHC. Fractographic evaluations by SEM revealed dimpled microstructures indicating ductile failures.
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