Published: Jan 1978
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A possible failure mode of high strength steels that are used in hydrogen gas-cooled turbine generators can be described by a combination of environment-assisted crack initiation, crack propagation by fatigue, and sustained load and final fracture. Therefore, a project was initiated to study the fracture properties in hydrogen and hydrogen sulfide (H2S) gas of two high strength steels, 3.5 nickel-chromium-molybdenum-vanadium ferritic and 18Mn-4Cr austenitic, which are commonly used for generator end rings. Two specimen types were employed, blunt notch specimens for crack initiation studies and precracked specimens for crack propagation and stress corrosion cracking studies. Tests were conducted to determine crack initiation due to incrementally rising load in H2S, crack propagation due to fatigue loading in hydrogen (H2), and KIscc in H2. This paper presents experimental data and provides metallurgical evidence to show that the failure mechanism in the specimens is environment assisted.
corrosion fatigue, crack propagation, nickel-base alloys, hydrogen embrittlement, fractography
Engineer, Fracture Mechanics, Ontario Hydro Research Laboratories, Toronto, Ontario,