Hydrogen Transport and Hydrogen Embrittlement in Stainless Steels (Diffusion, Permeation, Solubility, Slow Crack Growth)
Perng, Tsong-Pyng
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https://hdl.handle.net/2142/71819
Description
Title
Hydrogen Transport and Hydrogen Embrittlement in Stainless Steels (Diffusion, Permeation, Solubility, Slow Crack Growth)
Author(s)
Perng, Tsong-Pyng
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
In order to understand the kinetics of gaseous hydrogen-induced slow crack growth (SCG) in metastable austenitic stainless steels, hydrogen permeation and/or cracking velocity were measured and compared for three types of stainless steels. These included austenitic, ferritic, and duplex ((gamma)/(alpha)) alloys. Deformation in AISI 301 resulted in various amounts of (alpha)' martensite, which enhanced the effective hydrogen diffusivity and permeability. No phase transformation was observed in deformed AISI 310. The effective hydrogen diffusivity in this alloy was slightly reduced after plastic deformation, presumably by dislocation trapping. In either the dynamic or static tensile test, AISI 301 exhibited the greatest hydrogen embrittlement and therefore the highest SCG velocity among all the alloys tested in this work. The SCG velocity was believed to be controlled by the rate of accumulation of hydrogen in the embrittlement region ahead of the crack tip and therefore could be explained with the hydrogen transport parameters measured from the permeation experiments. The relatively high SCG velocity in AISI 301 was probably due to the fast transport of hydrogen through the primarily stress-induced (alpha)' phase around the crack. No SCG was observed in AISI 310. The presence of H(,2)O vapor was found to reduce both the hydrogen permeation and SCG velocity. The reduction was possibly caused by surface interference or oxidation, or a combination of these two effects. The mechanism of hydrogen-induced SCG was discussed based upon hydrogen-enhanced plasticity proposed by Beachem and Birnbaum. This concept was consistent with the SCG behavior in hydrogen gas observed in this work.
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