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Irradiation-assisted stress corrosion cracking of austenitic alloys

Technical Report ·
OSTI ID:7229262

An experimental program has been conducted to determine the mechanism of irradiation-assisted stress-corrosion cracking (IASCC) in austenitic stainless steel. High-energy protons have been used to produce grain boundary segregation and microstructural damage in samples of controlled impurity content. The densities of network dislocations and dislocation loops were determined by transmission electron microscopy and found to resemble those for neutron irradiation under LWR conditions. Grain boundary compositions were determined by in situ fracture and Auger spectroscopy, as well as by scanning transmission electron microscopy. Cr depletion and Ni segregation were observed in all irradiated samples, with the degree of segregation depending on the type and amount of impurities present. P, and to a lesser extent P, impurities were observed to segregate to the grain boundaries. Irradiation was found to increase the susceptibility of ultra-high-purity (UHP), and to a much lesser extent of UHP+P and UHP+S, alloys to intergranular SCC in 288{degree}C water at 2 ppm O{sub 2} and 0.5 {mu}S/cm. No intergranular fracture was observed in arcon atmosphere, indicating the important role of corrosion in the embrittlement of irradiated samples. The absence of intergranular fracture in 288{degree}C argon and room temperature tests also suggest that the embrittlement is not caused by hydrogen introduced by irradiation. Contrary to common belief, the presence of P impurities led to a significant improvement in IASCC over the ultrahigh purity alloy.

Research Organization:
Michigan Univ., Ann Arbor, MI (United States). Dept. of Nuclear Engineering
Sponsoring Organization:
DOE; USDOE, Washington, DC (United States)
DOE Contract Number:
FG07-88ER12825
OSTI ID:
7229262
Report Number(s):
DOE/ER/12825-2; ON: DE92040988
Country of Publication:
United States
Language:
English