High Pressure Gaseous Hydrogen Environment Research Articles

Hydrogen Embrittlement Characteristics of Tempered Martensitic Steels under Electrochemical and High-Pressure Hydrogen Environments

The effect of hydrogen charging methods on the hydrogen embrittlement characteristics of tempered martensitic steels were discussed in terms of hydrogen diffusion behavior. Two tempered martensitic steels with different Si content were fabricated by quenching and tempering. The steel with high Si content had a lower cementite fraction because the addition of Si changed the morphology of cementite from a long film-like shape to a short-rod shape by suppressing the precipitation and growth of the cementite. To evaluate the hydrogen embrittlement resistance of the two tempered martensitic steels with different Si content, slow strain-rate tensile testing was employed after introducing hydrogen using three types of hydrogen charging methods (ex-situ electrochemical hydrogen charging, in-situ electrochemical hydrogen charging, and in-situ high-pressure gaseous hydrogen environment). For the hydrogen pre-charged tensile specimens using the ex-situ electrochemical charging method, the steel with high Si content had a better hydrogen embrittlement resistance, with a higher relative reduction in area. On the other hand, there was no significant difference in the relative notch tensile strength of the two tempered martensitic steels with different Si content, regardless of the hydrogen charging methods. In addition, the ex-situ hydrogen charging method exhibited higher relative notch tensile strength compared to the in-situ hydrogen charging method due to the release of hydrogen during the tensile test, after exsitu hydrogen charging. This implies that hydrogen embrittlement resistance can be differently estimated depending on the kind of hydrogen charging methods.

Different augmentations of absorbed hydrogen under elastic straining in high-pressure gaseous hydrogen environment by as-quenched and as-tempered martensitic steels: combined experimental and simulation study

Hydrogen embrittlement (HE) behavior of as-quenched and as-tempered martensitic steels under elastic straining in a high-pressure gaseous hydrogen environment was studied for the first time. The difference in the total content of defects acting as H trap sites has the highest contribution to the increase in absorbed hydrogen content under the elastic loading. The hydrogen-induced fracture occurred in the as-quenched specimen during elastic straining in hydrogen environment, while the tempered specimen did not fracture under the elastic loading. Higher accumulation of the dislocations near the main crack initiation sites (prior austenite grain boundaries (PAGBs)) in the as-quenched specimen will be the main source of the hydrogen to the potential flaw to crack to initiate. H accumulated near PAGBs enhances dislocation slip along {011} planes and helps transgranular crack propagation. Due to less possibility to provide the critical local amount of hydrogen at PAGBs for the crack to initiate, the as-tempered specimen remained unfractured.

Dependence of the mechanical properties of a metastable austenitic stainless steel in high-pressure hydrogen gas on machining-induced defects

The susceptibility of metastable 304L to embrittlement in a high-pressure gaseous hydrogen environment was studied from the viewpoint of changes in mechanical properties. The high pressure hydrogen gas leads to deterioration of mechanical properties, which may be accelerated by the presence of surface defects. The tensile specimens were cut with different machining parameters to change the density of the different defects caused by the machining. The maximum dislocation density caused by machining, rather than the maximum strain-induced martensite increased the sensitivity to hydrogen embrittlement.

In-Situ Hollow Sample Setup Design for Mechanical Characterisation of Gaseous Hydrogen Embrittlement of Pipeline Steels and Welds

This work discusses the design and demonstration of an in-situ test setup for testing pipeline steels in a high pressure gaseous hydrogen (H2) environment. A miniature hollow pipe-like tensile specimen was designed that acts as the gas containment volume during the test. Specific areas of the specimen can be forced to fracture by selective notching, as performed on the weldment. The volume of H2 used was minimised so the test can be performed safely without the need of specialised equipment. The setup is shown to be capable of characterising Hydrogen Embrittlement (HE) in steels through testing an X60 pipeline steel and its weldment. The percentage elongation (%El) of the base metal was found to be reduced by 40% when tested in 100 barg H2. Reduction of cross-sectional area (%RA) was found to decrease by 28% and 11% in the base metal and weld metal, respectively, when tested in 100 barg H2. Benchmark test were performed at 100 barg N2 pressure. SEM fractography further indicated a shift from normal ductile fracture mechanisms to a brittle transgranular (TG) quasi-cleavage (QC) type fracture that is characteristic of HE.

高圧水素用高強度ステンレス鋼の溶接性

高圧水素用高強度ステンレス鋼の溶接性

Effects of chemical compositions and microstructure on hydrogen embrittlement of austenitic stainless steel weld metal in high-pressure gaseous hydrogen environment

The effect of chemical compositions and microstructures on hydrogen embrittlement of austenitic stainless steel weld metals in high-pressure hydrogen gas was surveyed by using the slow strain rate test (SSRT). As a result, hydrogen embrittlement of the weld metal was hardly influenced by δ ferrite in the weld metal, but by stability of austenite phase, which was estimated by Md30 value or Ni equivalent. In the weld metal with poor stability of austenite, α′-martensite was formed near a crack induced by SSRT. In addition, although the crystal structure of α′-martensite is as same as δ ferrite, susceptibility of hydrogen embrittlement became higher with the increase in α′-martensite. The mechanism to explain the difference between δ ferrite and α′-martensite was considered as following. The hardness, which increases the hydrogen embrittlement susceptibility in bcc structure, is higher in α′-martensite than in δ ferrite. In addition, α′-martensite might be formed continuously with propagation of a crack. Therefore, the effect of α′-martensite on hydrogen embrittlement could be larger compared with δ ferrite.

高圧水素ガス環境における低合金鋼の水素吸蔵挙動

高圧水素ガス環境における低合金鋼の水素吸蔵挙動

Influence of hydrogen environment on fatigue crack growth in forged Ti-6Al-4V: fractographic analysis

The influence of high-pressure gaseous hydrogen environment (15 MPa) on the fatigue crack growth in forged Ti-6A1-4V at room temperature is investigated. It is observed that the fatigue crack growth (FCG) rate is fluctuating at 20 ≤ ΔK ≤ 26 MPa√m, and increase drastically at ΔK > 26 MPa√m in hydrogen environment. The effect of hydrogen on the FCG rate is dependent on the stress intensity level (ΔK). Detailed fractographic analysis of the fracture surfaces is performed at different ΔK using field emission scanning electron microscope (FE-SEM). The differences in appearance of fracture surfaces in air and hydrogen are discussed.

高圧水素ガス環境下におけるオーステナイト系ステンレス鋼溶接金属の水素脆化に及ぼす化学成分および組織の影響

高圧水素ガス環境下におけるオーステナイト系ステンレス鋼溶接金属の水素脆化に及ぼす化学成分および組織の影響

Comparison of hydrogen embrittlement in three pipeline steels in high pressure gaseous hydrogen environments

The tensile properties of X52, X65, and X100 pipeline steels have been measured in a high-pressure (13.8MPa) hydrogen gas environment. Significant decreases in elongation at failure and reduction of area were observed when testing in hydrogen as compared with air, and those changes were accompanied by noticeable changes in fracture morphology. In addition to baseline characterization of the effects of strength and microstructure on the X52, X65, and X100 alloys, the influence of strain rate and hydrogen gas pressure was studied for only the X100 alloy.

Hydrogen Embrittlement Properties of Stainless and Low Alloy Steels in High Pressure Gaseous Hydrogen Environment

Recent research on Hydrogen Environment Embrittlement (HEE) susceptibility of stainless and low alloy steels in highly pressurized gaseous hydrogen environments was reviewed from the viewpoint of tensile properties, hydrogen absorption and fatigue properties.HEE susceptibility evaluated by Slow Strain Rate Test (SSRT) in high pressure hydrogen environments strongly depended on steel chemical compositions. Austenitic stainless steels such as type 316L or iron-based superalloy as A286 showed sufficient resistance to HEE, while stainless steels with low levels of alloying elements such as type 304L showed a remarkable ductility loss in high pressure gaseous hydrogen due to martensitic transformation. Martensitic stainless or low alloy steels also showed a remarkable ductility loss in gaseous hydrogen.Relationship between HEE susceptibility and an amount of hydrogen absorption was investigated. HEE susceptibility and hydrogen embrittlement under cathodic charging in aqueous solution showed the same dependence on the amount of hydrogen absorption, which implies HEE occurs by hydrogen absorption from external gaseous hydrogen environments.Fatigue properties in high pressure gaseous hydrogen environments were evaluated by means of internal or external pressurization tests. Austenitic stainless steels such as type 316L showed little decrease in fatigue life by hydrogen, while metastable stainless steel as type 304 or precipitation hardened superalloy as A286 showed degradation in fatigue life by hydrogen gas. Low alloy steel also showed a decrease in fatigue life in hydrogen, while high strength low alloy steel with much Mo and V showed longer fatigue life than conventional steel.

Fatigue Properties and Degradation Mechanism for Stainless and High Strength Steels in High Pressure Gaseous Hydrogen Environment

In order to ensure the safety of pipe and vessel used in high pressure gaseous hydrogen for fuel cell vehicles and hydrogen stations, material properties should be clarified and the mechanical structure needs to be designed. In this study, a cyclic pressurization fatigue test was conducted using tubular specimens in the high pressure gaseous hydrogen environment. Stable austenitic stainless steel SUS316L showed no degradation of fatigue life in high pressure gaseous hydrogen environment. In contrast, metastable austenitic stainless steel SUS304, precipitation hardening steel A-286 and low alloy steel SCM435 (high and low strength) showed degradation of fatigue life in high pressure gaseous hydrogen environment. Higher strengthened SCM435 showed degradation more significantly. It was clarified that the fatigue cracks grew along the interface between martensite phase and austenite phase in SUS304 with the use of Electron Back Scattering Diffraction Pattern (EBSD). Sub-cracks and intergranular fractures were observed in the fracture surface of A-286 which was tested in hydrogen environment. Intergranular fractures were observed in the fracture surface of high strengthened SCM435 and transgranular fractures were observed in the fracture surface of low strengthened SCM435 which was tested in hydrogen environment.

Degradation of fatigue properties in high pressure gaseous hydrogen environment evaluated by cyclic pressurization tests

Fatigue properties in high pressure gaseous hydrogen environment were investigated for pipe materials used in fuel cell vehicles and hydrogen stations. Cyclic pressurization tests were conducted using a tubular specimen filled with hydrogen pressurized up to 90MPa. Tested materials were types 316L, 304 and A286 stainless steels, low alloy steels such as JIS SCM435 (1.0Cr-0.2Mo), Cr-Mo-V steels. The fatigue life in hydrogen was compared with that in inert gas to evaluate the effect of gaseous hydrogen on fatigue properties. The fatigue life in hydrogen was slightly shorter than that in argon in the case of a stable stainless steel type 316L. In contrast, a metastable stainless steel type 304 showed a remarkable degradation of the fatigue life in the hydrogen environment. Although the fatigue lives in hydrogen of type 316L and 304 stainless steels decreased with the increase in the cycle times, the fatigue lives remained unchanged over 102 of the cycle time. The fatigue life of low alloy SCM435 steel in hydrogen extremely decreased. The fatigue life of high-strength austenitic steel A286 in hydrogen is much better than that of low alloy SCM435 steel at the same tensile strength. The Cr-Mo-V steels showed longer fatigue lives than JIS SCM 435 at same strength levels in hydrogen. Fracture surfaces revealed transgranular cracking for the Cr-Mo-V steels, while intergranular cracking was observed for SCM435 with tensile strength more than 1.2 GPa. It was assumed that the carbide precipitation affected the fracture morphology.

Bending Fatigue Test of Quenched and Tempered Chromium Molybdenum Steel(SCM435) under High Pressure Gaseous Hydrogen Environment

Bending Fatigue Test of Quenched and Tempered Chromium Molybdenum Steel(SCM435) under High Pressure Gaseous Hydrogen Environment

高圧水素ガス環境におけるステンレス鋼の脆化特性

燃料電池の実用化に向けての水素の輸送・貯蔵方法の一つとして高圧水素ガスを用いる方法が挙げられる. 本研究では, 高圧水素ガスシステムで使用される材料の安全性評価を目的として, アルミニウム合金およびオーステナイト系ステンレス鋼の機械的性質を45MPaの高圧水素ガス中の低ひずみ速度引張試験 (SSRT, Slow Strain Rate Testing) により調査した. アルミニウム合金A6061-T6および安定化オーステナイト系ステンレス鋼である316L鋼は低ひずみ速度条件下 (3×10-7～3×10-6s-1) でも脆化を示さなかった. 一方, 準安定オーステナイト系ステンレス鋼である304L鋼は, ひずみ誘起マルテンサイト相の生成により水素環境中で顕著な脆化を示した. 水素環境脆化特性は, 材料中への水素吸蔵と限界応力の観点から説明された.

A cumulative fatigue damage formulation for persistent slip band type materials: Cordero, L. Ahmadieh, A. and Mazumdar, P.K. Scr. Metall. Nov. 1988 22, (11), 1761–1764

Fatigue properties in high pressure gaseous hydrogen environment were investigated for pipe materials used in fuel cell vehicles and hydrogen stations. Cyclic pressurization tests were conducted using a tubular specimen filled with hydrogen pressurized up to 90MPa. Tested materials were types 316L, 304 and A286 stainless steels, low alloy steels such as JIS SCM435 (1.0Cr-0.2Mo), Cr-Mo-V steels. The fatigue life in hydrogen was compared with that in inert gas to evaluate the effect of gaseous hydrogen on fatigue properties. The fatigue life in hydrogen was slightly shorter than that in argon in the case of a stable stainless steel type 316L. In contrast, a metastable stainless steel type 304 showed a remarkable degradation of the fatigue life in the hydrogen environment. Although the fatigue lives in hydrogen of type 316L and 304 stainless steels decreased with the increase in the cycle times, the fatigue lives remained unchanged over 102 of the cycle time. The fatigue life of low alloy SCM435 steel in hydrogen extremely decreased. The fatigue life of high-strength austenitic steel A286 in hydrogen is much better than that of low alloy SCM435 steel at the same tensile strength. The Cr-Mo-V steels showed longer fatigue lives than JIS SCM 435 at same strength levels in hydrogen. Fracture surfaces revealed transgranular cracking for the Cr-Mo-V steels, while intergranular cracking was observed for SCM435 with tensile strength more than 1.2 GPa. It was assumed that the carbide precipitation affected the fracture morphology.