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Relationship between hydrogen‐assisted crack propagation rate and the corresponding crack path in AISI 4340 steel
Author(s) -
Pyun SuII,
Lie HyoGun
Publication year - 1990
Publication title -
steel research
Language(s) - English
Resource type - Journals
eISSN - 1869-344X
pISSN - 0177-4832
DOI - 10.1002/srin.199000371
Subject(s) - path (computing) , materials science , metallurgy , hydrogen , forensic engineering , composite material , structural engineering , engineering , chemistry , computer science , organic chemistry , programming language
In the present investigation, relationship between hydrogen‐assisted (HA) crack propagation rate and the corresponding fracture mode in AISI 4340 steel has been elucidated with critical hydrogen concentration concept. Hydrogen assisted crack‐propagation rate and the corresponding fracture surface morphology were determined from double cantilever beam (DCB) specimens as a function of hydrogen pressure and temperature. As hydrogen pressure decreased, threshold stress intensity factor necessary for the onset of hydrogen‐assisted crack propagation increased and the stage II (plateau) crack‐propagation rate decreased. The kinetics of stage II crack propagation indicated substantial difference, i.e., positive and negative responses in the two investigated low and high temperature regions, respectively. Fractographic analysis showed that increased amounts of the microvoid coalescence mode resulted in slower crack‐propagation rates. The observed changes in crack‐propagation rate and the corresponding fracture mode with hydrogen pressure and temperature are discussed in terms of critical stress or strain and critical hydrogen concentration concepts.