The Mechanism of Hydrogen Embrittlement in Nickel.
Final technical rept. Jan-Jun 75,
IMPERIAL COLL OF SCIENCE AND TECHNOLOGY LONDON (ENGLAND) DEPT OF METALLURGY AND MATERIALS ACIENCE
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Grain boundary cracking associated with the decomposition of nickel hydride in cathodically charged nickel was studied in the high voltage electron microscope. The occurrence of grain boundary cracking comes about from the presence of hydrogen at the boundaries and is not solely the result of the local boundary tensile stress due to the 5 difference in lattice parameter between the nickel and the hydride phases. In thin foil specimens grain boundary cracking occurs in the period of a few minutes after the end of cathodic charging, and does not continue in electron transparent regions during observation in the high voltage microscope. The susceptibility of grain boundaries to hydrogen-induced cracking is strongly dependent upon the structure of the boundary. Special boundaries, such as that of a twin, are particularly resistant to cracking.
- Metallurgy and Metallography