Effects of External Hydrogen on Hydrogen Transportation and Distribution Around the Fatigue Crack Tip in Type 304 Stainl
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Effects of External Hydrogen on Hydrogen Transportation and Distribution Around the Fatigue Crack Tip in Type 304 Stainless Steel Xingyang Chen, Chengshuang Zhou, Xiao Cai, Jinyang Zheng, and Lin Zhang (Submitted April 20, 2017; in revised form July 11, 2017; published online September 25, 2017) The effects of external hydrogen on hydrogen transportation and distribution around the fatigue crack tip in type 304 stainless steel were investigated by using hydrogen microprint technique (HMT) and thermal desorption spectrometry. HMT results show that some silver particles induced by hydrogen release are located near the fatigue crack and more silver particles are concentrated around the crack tip, which indicates that hydrogen accumulates in the vicinity of the crack tip during the crack growth in hydrogen gas environment. Along with the crack propagation, strain-induced a¢ martensite forms around the crack tip and promotes hydrogen invasion into the matrix, which will cause the crack initiation and propagation at the austenite/a¢ martensite interface. In addition, the hydrogen content in the vicinity of the crack tip is higher than that at the crack edge far away from the crack tip, which is related to the stress state and straininduced a¢ martensite. Keywords
crack initiation, hydrogen distribution, hydrogen environment embrittlement, hydrogen microprint technique, strain-induced a¢ martensite
1. Introduction Storage, transportation and filling of hydrogen safely are the key problems of large-scale use of hydrogen energy. Among them, high-pressure hydrogen storage has the advantage of simple structure, low energy consumption and high gas filling– discharging speed. At present, the high-pressure hydrogen (35 or 70 MPa) storage filling system is widely used in fuel cell vehicles, hydrogen filling stations and fuel cell power stations, where the metals are always exposed to hydrogen (Ref 1). Austenitic stainless steels (such as type 304, 316, 316L) are widely used as the material of storage hydrogen tank, pressure gage, gas pipeline, and so on. It is well known that the highpressure hydrogen gas can cause the failure of materials used in the high-pressure hydrogen system because of hydrogen environment embrittlement (HEE) (Ref 2-9). HEE of metals depends on hydrogen invasion from the surface into metals. The failure of material due to HEE is a series of complex processes: gaseous hydrogen transport, physical adsorption, dissociation of hydrogen molecules, chemisorption, hydrogen diffusion and segregation, hydrogen-induced crack initiation and crack propagation. The fatigue crack growth (FCG) rate in austenitic stainless steel can be significantly increased in the presence of hydrogen. Perng and Altstetter (Ref 10) pointed out that strain-induced a¢ Xingyang Chen, Chengshuang Zhou, Xiao Cai, and Lin Zhang, Institute of Material Forming and Control Engineering, Zhejiang University of Technology, Hangzhou 310014, China; and Jinyang Zheng, Institute of Chemical Machinery Engineering, Zhejiang
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