Intergranular embrittlement of Alloy 600 has been studied by pre-exposing thin foils, 20-30 μm thick, in high-pressure steam/hydrogen at 400°C, then fracturing them at room temperature. Hydrogen egress was believed to be complete before fracture, so any embrittlement was due to irreversible damage at the grain boundaries. Embrittlement was observed in both as-received and cold-worked material, to a depth of a few microns. The kinetics of this embrittlement are insufficient to account for stress corrosion velocities measured in this environment, unless one postulates an improbably frequent crack advance. The most likely cause of embrittlement is selective intergranular oxidation of chromium. Various other internal embrittlement processes are discussed.

Subject
Embrittlement, Foil, Materials, Autoclaves, Micrography, Stress cracking, Kinetics, Specimen preparation, Internal oxidation, Grain boundary, Alloys, Hydrogen, Oxidation
Keywords:
stress-corrosion cracking, Alloy 600, embrittlement
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1994
Association for Materials Protection and Performance (AMPP)
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