Hydrogen Transport and Hydrogen Embrittlement in Stainless Steels (Diffusion, Permeation, Solubility, Slow Crack Growth)

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.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Metallurgical Engineering

Grantor

University of Illinois at Urbana-Champaign

Date dc:date

10000-01-01

Author dc:creator

• Perng, Tsong-Pyng

• Engineering, Metallurgy

Identifier

(UMI)AAI8511659

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/71819