Effect of hydrogen on tensile behavior of low alloy steel in the regime of dynamic strain ageing

Gorja Sudhakar Rao, Hans Peter Seifert, Stefan Ritter, Philippe Spätig, Zaiqing Que

Research output: Contribution to journalArticleScientificpeer-review

6 Citations (Scopus)

Abstract

Low alloy steels typically used for reactor pressure vessel (RPV) in light water reactors may undergo different degradations and ageing mechanisms during service like fatigue, strain-induced corrosion cracking and corrosion fatigue or irradiation embrittlement, the latter being recognized as life limiting factor. There is growing concern that hydrogen, absorbed from the high temperature water environment and corrosion reactions, may potentially reduce toughness of RPV steels in synergy (or competition) with other embrittlement mechanisms like irradiation embrittlement, thermal ageing or dynamic strain aging (DSA). Strain rate, temperature and occurrence of DSA in these steels may affect the severity of the effect of hydrogen on toughness. The present investigation was envisaged to characterize the effect of hydrogen on tensile and fracture behavior of low alloy RPV steels at different strain rates and temperatures with a special emphasis on the synergy between DSA and hydrogen embrittlement. For this reason, tensile tests were carried out with as-received and hydrogen pre-charged specimens between 25 and 400 °C and at strain rates between 10 -1 and 10 -6 s -1 . The fracture mode was evaluated by detailed post-test fractography in the scanning electron microscope. DSA in these steels was established by the occurrence of serrations, negative strain-rate sensitivity and a maximum/minimum in strength/ductility at intermediate temperatures and strain rates. The DSA peak and range were found to be shifted to lower temperatures with decreasing strain rates and vice-versa. The hydrogen pre-charging resulted in marginal softening and strain-rate dependent reduction in ductility at 250/288 °C. The hydrogen embrittlement and reduction in ductility were more pronounced and the strain rate range for hydrogen embrittlement significantly extended in the RPV steel with higher DSA susceptibility demonstrating some synergy between DSA and hydrogen effects, probably due to the localization of plastic deformation. In presence of hydrogen, shear dominated ductile fracture (microvoid coalescence) with varying amounts of quasi-cleavage regions and secondary cracking along the prior austenite grain boundaries were observed. A detailed investigation on these aspects and a tentative mechanistic explanation is presented in this paper.
Original languageEnglish
Pages (from-to)3399-3406
Number of pages8
JournalProcedia: Structural Integrity
Volume2
DOIs
Publication statusPublished - 2016
MoE publication typeA1 Journal article-refereed

Fingerprint

High strength steel
Strain rate
Aging of materials
Hydrogen
Hydrogen embrittlement
Embrittlement
Steel structures
Ductility
Toughness
Temperature
Irradiation
Fractography
Corrosion fatigue
Thermal aging
Light water reactors
Ductile fracture
Steel
Stress corrosion cracking
Pressure vessels
Coalescence

Keywords

  • Reactor pressure vessel steels
  • dynamic strain aging
  • fracture
  • hydrogen embrittlement
  • intergrannular cracking

Cite this

Sudhakar Rao, Gorja ; Seifert, Hans Peter ; Ritter, Stefan ; Spätig, Philippe ; Que, Zaiqing. / Effect of hydrogen on tensile behavior of low alloy steel in the regime of dynamic strain ageing. In: Procedia: Structural Integrity. 2016 ; Vol. 2. pp. 3399-3406.
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abstract = "Low alloy steels typically used for reactor pressure vessel (RPV) in light water reactors may undergo different degradations and ageing mechanisms during service like fatigue, strain-induced corrosion cracking and corrosion fatigue or irradiation embrittlement, the latter being recognized as life limiting factor. There is growing concern that hydrogen, absorbed from the high temperature water environment and corrosion reactions, may potentially reduce toughness of RPV steels in synergy (or competition) with other embrittlement mechanisms like irradiation embrittlement, thermal ageing or dynamic strain aging (DSA). Strain rate, temperature and occurrence of DSA in these steels may affect the severity of the effect of hydrogen on toughness. The present investigation was envisaged to characterize the effect of hydrogen on tensile and fracture behavior of low alloy RPV steels at different strain rates and temperatures with a special emphasis on the synergy between DSA and hydrogen embrittlement. For this reason, tensile tests were carried out with as-received and hydrogen pre-charged specimens between 25 and 400 °C and at strain rates between 10 -1 and 10 -6 s -1 . The fracture mode was evaluated by detailed post-test fractography in the scanning electron microscope. DSA in these steels was established by the occurrence of serrations, negative strain-rate sensitivity and a maximum/minimum in strength/ductility at intermediate temperatures and strain rates. The DSA peak and range were found to be shifted to lower temperatures with decreasing strain rates and vice-versa. The hydrogen pre-charging resulted in marginal softening and strain-rate dependent reduction in ductility at 250/288 °C. The hydrogen embrittlement and reduction in ductility were more pronounced and the strain rate range for hydrogen embrittlement significantly extended in the RPV steel with higher DSA susceptibility demonstrating some synergy between DSA and hydrogen effects, probably due to the localization of plastic deformation. In presence of hydrogen, shear dominated ductile fracture (microvoid coalescence) with varying amounts of quasi-cleavage regions and secondary cracking along the prior austenite grain boundaries were observed. A detailed investigation on these aspects and a tentative mechanistic explanation is presented in this paper.",
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Effect of hydrogen on tensile behavior of low alloy steel in the regime of dynamic strain ageing. / Sudhakar Rao, Gorja; Seifert, Hans Peter; Ritter, Stefan; Spätig, Philippe; Que, Zaiqing.

In: Procedia: Structural Integrity, Vol. 2, 2016, p. 3399-3406.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Effect of hydrogen on tensile behavior of low alloy steel in the regime of dynamic strain ageing

AU - Sudhakar Rao, Gorja

AU - Seifert, Hans Peter

AU - Ritter, Stefan

AU - Spätig, Philippe

AU - Que, Zaiqing

PY - 2016

Y1 - 2016

N2 - Low alloy steels typically used for reactor pressure vessel (RPV) in light water reactors may undergo different degradations and ageing mechanisms during service like fatigue, strain-induced corrosion cracking and corrosion fatigue or irradiation embrittlement, the latter being recognized as life limiting factor. There is growing concern that hydrogen, absorbed from the high temperature water environment and corrosion reactions, may potentially reduce toughness of RPV steels in synergy (or competition) with other embrittlement mechanisms like irradiation embrittlement, thermal ageing or dynamic strain aging (DSA). Strain rate, temperature and occurrence of DSA in these steels may affect the severity of the effect of hydrogen on toughness. The present investigation was envisaged to characterize the effect of hydrogen on tensile and fracture behavior of low alloy RPV steels at different strain rates and temperatures with a special emphasis on the synergy between DSA and hydrogen embrittlement. For this reason, tensile tests were carried out with as-received and hydrogen pre-charged specimens between 25 and 400 °C and at strain rates between 10 -1 and 10 -6 s -1 . The fracture mode was evaluated by detailed post-test fractography in the scanning electron microscope. DSA in these steels was established by the occurrence of serrations, negative strain-rate sensitivity and a maximum/minimum in strength/ductility at intermediate temperatures and strain rates. The DSA peak and range were found to be shifted to lower temperatures with decreasing strain rates and vice-versa. The hydrogen pre-charging resulted in marginal softening and strain-rate dependent reduction in ductility at 250/288 °C. The hydrogen embrittlement and reduction in ductility were more pronounced and the strain rate range for hydrogen embrittlement significantly extended in the RPV steel with higher DSA susceptibility demonstrating some synergy between DSA and hydrogen effects, probably due to the localization of plastic deformation. In presence of hydrogen, shear dominated ductile fracture (microvoid coalescence) with varying amounts of quasi-cleavage regions and secondary cracking along the prior austenite grain boundaries were observed. A detailed investigation on these aspects and a tentative mechanistic explanation is presented in this paper.

AB - Low alloy steels typically used for reactor pressure vessel (RPV) in light water reactors may undergo different degradations and ageing mechanisms during service like fatigue, strain-induced corrosion cracking and corrosion fatigue or irradiation embrittlement, the latter being recognized as life limiting factor. There is growing concern that hydrogen, absorbed from the high temperature water environment and corrosion reactions, may potentially reduce toughness of RPV steels in synergy (or competition) with other embrittlement mechanisms like irradiation embrittlement, thermal ageing or dynamic strain aging (DSA). Strain rate, temperature and occurrence of DSA in these steels may affect the severity of the effect of hydrogen on toughness. The present investigation was envisaged to characterize the effect of hydrogen on tensile and fracture behavior of low alloy RPV steels at different strain rates and temperatures with a special emphasis on the synergy between DSA and hydrogen embrittlement. For this reason, tensile tests were carried out with as-received and hydrogen pre-charged specimens between 25 and 400 °C and at strain rates between 10 -1 and 10 -6 s -1 . The fracture mode was evaluated by detailed post-test fractography in the scanning electron microscope. DSA in these steels was established by the occurrence of serrations, negative strain-rate sensitivity and a maximum/minimum in strength/ductility at intermediate temperatures and strain rates. The DSA peak and range were found to be shifted to lower temperatures with decreasing strain rates and vice-versa. The hydrogen pre-charging resulted in marginal softening and strain-rate dependent reduction in ductility at 250/288 °C. The hydrogen embrittlement and reduction in ductility were more pronounced and the strain rate range for hydrogen embrittlement significantly extended in the RPV steel with higher DSA susceptibility demonstrating some synergy between DSA and hydrogen effects, probably due to the localization of plastic deformation. In presence of hydrogen, shear dominated ductile fracture (microvoid coalescence) with varying amounts of quasi-cleavage regions and secondary cracking along the prior austenite grain boundaries were observed. A detailed investigation on these aspects and a tentative mechanistic explanation is presented in this paper.

KW - Reactor pressure vessel steels

KW - dynamic strain aging

KW - fracture

KW - hydrogen embrittlement

KW - intergrannular cracking

U2 - 10.1016/j.prostr.2016.06.424

DO - 10.1016/j.prostr.2016.06.424

M3 - Article

VL - 2

SP - 3399

EP - 3406

JO - Procedia: Structural Integrity

JF - Procedia: Structural Integrity

SN - 2452-3216

ER -