TY - JOUR
T1 - Macro- and microscale investigations of hydrogen embrittlement in X70 pipeline steel by in-situ and ex-situ hydrogen charging tensile tests and in-situ electrochemical micro-cantilever bending test
AU - Asadipoor, M.
AU - Pourkamali Anaraki, A.
AU - Kadkhodapour, J.
AU - Sharifi, S. M.H.
AU - Barnoush, A.
N1 - Publisher Copyright:
© 2019
PY - 2020/1/20
Y1 - 2020/1/20
N2 - The effect of hydrogen on the mechanical properties of X70 pipeline steel was investigated by a combination of macro- and microscale approaches. Various tensile tests under vacuum, in-situ H-plasma charging (IHPC), and ex-situ electrochemical H-charging (EEHC) conditions were conducted to elucidate the hydrogen effect in the macroscale approach. All tensile tests were performed inside an environmental scanning electron microscopy (ESEM) chamber. The IHPC, as a novel hydrogen charging technique, was compared with conventional EEHC while uncharged tensile specimens were used as a reference. The results demonstrated that the variations in the IHPC condition were negligible compared to the vacuum condition, whereas the differences in the ex-situ condition were more prominent. Furthermore, susceptibility to hydrogen in the vacuum-ex situ regime was manifested in the reduction of yield strength and ultimate tensile strength. These findings were confirmed by the fractographic analysis, where some of the effects of hydrogen (e.g. the formation of secondary cracks by detrimental inclusions (MnS and Al2O3) and the transition of fracture features from ductile dimples to cleavage patterns) were well illustrated. On the other hand, micro-cantilever bending tests were performed in the air to avoid hydrogen effects and applied inside a miniaturized electrochemical cell to promote hydrogen uptake. The bending results and post-mortem analysis of the tested cantilevers indicated that the hydrogen-reduced flow stress and hydrogen-induced cracking occurred for the H-charged bent cantilever, while only increased plastic behavior occurred for the cantilever bent in the air.
AB - The effect of hydrogen on the mechanical properties of X70 pipeline steel was investigated by a combination of macro- and microscale approaches. Various tensile tests under vacuum, in-situ H-plasma charging (IHPC), and ex-situ electrochemical H-charging (EEHC) conditions were conducted to elucidate the hydrogen effect in the macroscale approach. All tensile tests were performed inside an environmental scanning electron microscopy (ESEM) chamber. The IHPC, as a novel hydrogen charging technique, was compared with conventional EEHC while uncharged tensile specimens were used as a reference. The results demonstrated that the variations in the IHPC condition were negligible compared to the vacuum condition, whereas the differences in the ex-situ condition were more prominent. Furthermore, susceptibility to hydrogen in the vacuum-ex situ regime was manifested in the reduction of yield strength and ultimate tensile strength. These findings were confirmed by the fractographic analysis, where some of the effects of hydrogen (e.g. the formation of secondary cracks by detrimental inclusions (MnS and Al2O3) and the transition of fracture features from ductile dimples to cleavage patterns) were well illustrated. On the other hand, micro-cantilever bending tests were performed in the air to avoid hydrogen effects and applied inside a miniaturized electrochemical cell to promote hydrogen uptake. The bending results and post-mortem analysis of the tested cantilevers indicated that the hydrogen-reduced flow stress and hydrogen-induced cracking occurred for the H-charged bent cantilever, while only increased plastic behavior occurred for the cantilever bent in the air.
KW - Ex-situ electrochemical hydrogen charging
KW - Hydrogen embrittlement
KW - In-situ hydrogen plasma charging
KW - Micro-cantilever bending test
KW - Ultimate tensile strength
KW - Yield strength
UR - http://www.scopus.com/inward/record.url?scp=85075798619&partnerID=8YFLogxK
U2 - 10.1016/j.msea.2019.138762
DO - 10.1016/j.msea.2019.138762
M3 - Article
AN - SCOPUS:85075798619
SN - 0921-5093
VL - 772
JO - Materials Science and Engineering: A
JF - Materials Science and Engineering: A
M1 - 138762
ER -