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https://hdl.handle.net/2142/71816
Description
Title
Hydrogen Embrittlement of Nickel
Author(s)
Lassila, David H.
Issue Date
1985
Department of Study
Metallurgy and Mining Engineering
Discipline
Metallurgical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Metallurgy
Abstract
Experiments were performed to determine the effects of hydrogen segregation at grain boundaries on intergranular fracture of charged nickel deformed in tension. Two modes of hydrogen segregation are investigated; lattice diffusion and dislocation transport of "Cottrell atmospheres" of hydrogen. The effect of cosegregation of hydrogen and sulfur is also explored.
The results of this study show that the parameters affecting the diffusive segregation of hydrogen to grain boundaries play a fundamental role in conditions which result in embrittlement. If a sufficient quantity of hydrogen at grain boundaries is attained, the fracture mode of nickel will change from ductile rupture to intergranular. Experiments performed to evaluate the role of dislocation transport of hydrogen in the embrittlement of nickel suggest that dislocation transport has no effect on embrittlement and that the embrittlement mechanism is not dependent on hydrogen mobility.
An analysis of the thermodynamics and kinetics of hydrogen segregation yielded values for the binding enthalpy of hydrogen to nickel grain boundaries and the breadth of hydrogen enhancement at boundaries. By considering these values and other test results a mechanism of hydrogen embrittlement of nickel is proposed.
Three series of nickel tensile specimens were tested with various amounts of sulfur segregation present at grain boundaries. Segregation on the order of 0.1 monolayer has been shown to severely increase the embrittlement susceptibility of hydrogen charged nickel.
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