A Nucleation Mechanism of Hydrogen Blister in Metals and Alloys
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INTRODUCTION
THE occurrence of ‘‘flakes’’ or ‘‘hair-line cracks’’ in large forging and rolling parts of steels has been investigated for many years.[1–3] The hydrogen-induced blisters in medium strength steel during cathodic charging or in contact with wet hydrogen sulphide (H2S) has also been widely studied.[4–6] The internal fissures are believed to be induced by combination of atomic hydrogen at high concentration resulting in molecular hydrogen formation.[7,8] Furthermore, hydrogen blister or crack appears in many other materials in the absence of external stress if the hydrogen concentration is high enough. Panagopoulos et al.[9] observed the cracking and blistering of a-brass induced by cathodic hydrogen charging. The blisters in AISI 304[10] and 430[11] stainless steel induced by cathodic hydrogen charging has been reported. Solovioff et al.[13] found the formation and growth of hydrogen-induced blister in nickel preimplanted with helium. Recently, Shan et al.[12] observed the hydrogen-induced blisters of metallic glass precharged in solution by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Hydrogen blister formation and subsequent cracking X.C. REN, Lecturer, and W.Y. CHU, J.X. LI, Y.J. SU, and L.J. QIAO, Professors, are with University of Science and Technology Beijing, Beijing 100083, People s Republic of China. Contact e-mail: [email protected] Q.J. ZHOU, Engineer, formerly with University of Science and Technology Beijing, Beijing 100083, People s Republic of China, is with the R&D Center, Baoshan Iron & Steel Co., Ltd., Shanghai 201900, People s Republic of China. G.B. SHAN, Engineer, formerly with University of Science and Technology Beijing, Beijing 100083, People s Republic of China, is with the SINOPEC Safety Engineering Institute, Qingdao 266071, People s Republic of China. Manuscript submitted January 19, 2007. Article published online November 15, 2007 METALLURGICAL AND MATERIALS TRANSACTIONS A
and exfoliation behavior for nickel and various tungsten materials under hydrogen plasma exposure has been a serious concern in commercial reactors.[13,14] Now hydrogen-induced blister in hydrogen-implanted silicon has been used as a method for the fabrication of siliconon-insulator material in semiconductor industry.[15,16] Hydrogen blister was even observed in diamond implanted with hydrogen ions.[17] The mechanism of the hydrogen-induced blisters or cracks has been discussed widely. Most of the mechanisms are based on the internal pressure theory suggested by Zapffe et al.[18] and Tetelman.[19] Garofalo et al.[20] proposed that hydrogen embrittlement and propagation of internal cracks in iron and steel are promoted by hydrogen gas in voids or microcracks that may be formed by plastic deformation. Their calculation showed that a Stroh crack ceased to be stable when a critical internal pressure was reached in the absence of an external stress. For metals experiencing cold working, whose many microvoids or microcracks are induced by plastic deformation, this mechanism is r
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