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The purpose of this paper is to demonstrate the effect of δ-ferrite on the susceptibility to hydrogen embrittlement of type 304 stainless steel in hydrogen gas environment.

The mechanical properties of as-received and solution-treated specimens were investigated by the test of tensile and fatigue crack growth (FCG) in 5 MPa argon and hydrogen.

The presence of δ-ferrite reduced the relative elongation and the relative reduction area (H₂/Ar) of 304 stainless steel, indicating that δ-ferrite increased the susceptibility of hydrogen embrittlement in 304 stainless steel. Moreover, δ-ferrite promoted the fatigue crack initiation and propagation at the interface between δ-ferrite and austenite. The FCG tests were used to investigate the effect of δ-ferrite on the FCG rate in hydrogen gas environment, and it was found that δ-ferrite accelerated the FCG rate, which was attributed to rapid diffusion and accumulation of hydrogen around the fatigue crack tip through δ-ferrite in high-pressure hydrogen gas environment.

The dependence of the susceptibility to hydrogen embrittlement on δ-ferrite was first investigated in type 304 steel in hydrogen environment with high pressures, which provided the basis for the design and development of a high strength, hydrogen embrittle-resistant austenitic stainless steel.

The purpose of this paper is to present a crack initiation mechanism of the external hydrogen effect on type 304 stainless steel, as well as on fatigue crack propagation in the presence of hydrogen gas.

The effects of external hydrogen on hydrogen-assisted crack initiation in type 304 stainless steel were discussed by performing fatigue crack growth rate and fatigue life tests in 5 MPa argon and hydrogen.

Hydrogen can reduce the incubation period of fatigue crack initiation of smooth fatigue specimens and greatly promote the fatigue crack growth rate during the subsequent fatigue cycle. During the fatigue cycle, hydrogen invades into matrix through the intrusion and extrusion and segregates at the boundaries of α′ martensite and austenite. As the fatigue cycle increased, hydrogen-induced cracks would initiate along the slip bands. The crack initiation progress would greatly accelerate in the presence of hydrogen.

To the best of the authors’ knowledge, this paper is an original work carried out by the authors on the hydrogen environment embrittlement of type 304 stainless steel. The effects of external hydrogen and argon were compared to provide understanding on the hydrogen-assisted crack initiation behaviors during cycle loading.

The purpose of this study is to investigate the effect of ferrite on hydrogen embrittlement (HE) of the 17-4PH stainless steels.

The effects of ferrite on HE of the 17-4PH stainless steels were investigated by observing microstructure and conducting slow-strain-rate tensile tests and hydrogen permeability tests.

The microstructure of the ferrite-bearing sample is lath martensite and banded ferrite, and the ferrite-free sample is lath martensite. After hydrogen charging, the plasticity of the two steels is significantly reduced, along with the tensile strength of the ferrite-free sample. The HE susceptibility of the ferrite-bearing sample is significantly lower than the ferrite-free steel, and the primary fracture modes gradually evolved from typical dimple to quasi-cleavage and intergranular cracking. After aging at 480°C for 4 h and hydrogen charging for 12 h, the 40.9% HE susceptibility of ferrite-bearing samples was the lowest. In addition, the hydrogen permeation tests show that ferrite is a fast diffusion channel for hydrogen, and the ferrite-bearing samples have higher effective hydrogen diffusivity and lower hydrogen concentration.

There are a few studies of the ferrite effect on the HE properties of martensitic precipitation hardening stainless steel.

The full development of marine technologies for the industrial exploitation of deep‐sea resources requires the availability of exhaustive engineering data on the degradation of constructional materials when immersed at great length in ocean environments. An overall review of behavioural figures from reliable sources allows to point out major weaknesses and uncertainties with candidate alloys and consequent demands for ameliorative and innovative investigation. Prominent objects of research can be envisaged, accordingly, in: (i) formulating low‐alloy steels whose surface is chemically convertible (by suitable pretreatments or free corrosion itself) so as to abate the rate of oxygen cathodic reduction i.e. the current density required for cathodic protection; (ii) singling out high‐strength steels whose resistance to corrosion‐fatigue and hydrogen embrittlement is in proportion to the strength level; (iii) developing cheaper alternatives to high‐molybdenum stainless alloys resistant to localised corrosion; (iii) combining (in optimal composites) the outstanding resistance of titanium to saltwater corrosion and the low‐cost good mechanical properties of steels.

Aqueous solutions which contain H2SO4, H2S or mixtures of H2S and NH3 are corrosive to carbon steel and other commonly used alloys. Therefore, titanium has been evaluated as a possible construction material in these environments. This paper summarizes the results of a study of the corrosion, galvanic and hydrogen embrittlement behaviour of titanium in aqueous sulfidic and sulfate solutions. Variables discussed include the effect of solution pH, temperature and solution composition on the corrosion and electro chemical behaviour including galvanic effects of titanium. This paper also considers the effect of pH, temperature and mechanical loading rate (strain‐rate) on the ductility and embrittlement of titanium.

With excellent mechanic properties and hydrogen embrittlement (HE) resistance, 12Cr2Mo1R(H) steel is suitable to make hot-wall hydrogenation reactors. However, longtime exposure to a harsh environment of high-pressure hydrogen at medium temperature in practical application would still induce severe hydrogen uptake and eventually damage the mechanical properties of the steel. The study aims to evaluate the HE resistance of the steel under different tensile strain rates after hydrogen charging and analyze the hydrogen effect from atomic level.

This research studied the HE properties of 12Cr2Mo1R(H) steel by slow strain rate tests. Meanwhile, the effect of hydrogen on the structures and the mechanical properties of the simplified models of the steel was also investigated by first-principle calculations.

Experimental results showed that after hydrogen pre-charging in this work, hydrogen had little effect on the microstructure of the steel. The elongations and reduction of cross-sectional area of the samples reduced a lot, by contrast, the yield and tensile strengths changed slightly. The 12Cr2Mo1R(H) steel was not very susceptible to HE with a maximum embrittlement index of about 20.00%. First principles calculation results showed that after H dissolution, lattice distortion occurred and interstitial H atoms would preferentially occupy the tetrahedral interstitial site in bcc-Fe crystal and increase the stability of the supercells. With the increase of H atoms added into the simplified model, the steel still possessed a good ductility and toughness at a low hydrogen concentration, while the material would become brittle as the concentration of hydrogen continued to increase.

These finds can provide valuable information for subsequent HE studies on this steel.

12Cr2Mo1R(H) steel is commonly used to make hot-wall hydrogenation reactors given its excellent mechanical properties and hydrogen embrittlement (HE) resistance. Longtime exposure to high-pressure hydrogen at medium temperature would still severely damage the mechanical properties of the Cr-Mo steel with surface HICs caused by hydrogen adsorption and hydrogen uptake. The mechanisms of HE remain controversial and have not been fully understood so far.

The HE of the steel was investigated by slow strain rate test at different strain rates with in situ hydrogen charging. The diffusion coefficient of hydrogen in the steel is measured by electrochemical technology of hydrogen permeation. HIC cracks of the fractured specimens were captured with field emission SEM equipped with an electron backscatter diffraction system.

Results showed that the hydrogen led to the plasticity of the samples reduced significantly, together with the distinct work hardening behavior induced by hydrogen charging during plastic flow stage. The fracture of in situ charged sample changes from quasi-cleavage to intergranular fracture with the decreasing of strain rates, which indicates that the steel become more susceptible to hydrogen. High densities of dislocations and deformation are found around the crack, where grains are highly sensitive to HIC. Grains with different Taylor factor are more susceptible to intergranular crack.

The results of the study would be helpful to a safer application of the steel.

A simple economic analysis has revealed that in order for wind energy to be a viable alternative, wind-turbines (convertors of wind energy into electrical energy) must be able to operate for at least 20 years, with only regular maintenance. However, wind-turbines built nowadays do not generally possess this level of reliability and durability. Specifically, due to the malfunction and failure of drive-trains/gear-boxes, many wind-turbines require major repairs after only three to five years in service. The paper aims to discuss these issues.

The subject of the present work is the so-called white etch cracking, one of the key processes responsible for the premature failure of gear-box roller-bearings. To address this problem, a multi-physics computational methodology is developed and used to analyze the problem of wind-turbine gear-box roller-bearing premature-failure. The main components of the proposed methodology include the analyses of: first, hydrogen dissolution and the accompanying grain-boundary embrittlement phenomena; second, hydrogen diffusion from the crack-wake into the adjacent unfractured material; third, the inter-granular fracture processes; and fourth, the kinematic and structural response of the bearing under service-loading conditions.

The results obtained clearly revealed the operation of the white-etch cracking phenomenon in wind-turbine gear-box roller-bearings and its dependence on the attendant loading and environmental conditions.

The present work attempts to make a contribution to the resolution of an important problem related to premature-failure and inferior reliability of wind-turbine gearboxes.

This paper aims to use an imidazole-based n-ionic Gemini surfactant derived from palm oil to inhibit the sulfide stress corrosion cracking of a supermartensitic stainless steel.

The slow strain rate testing technique, hydrogen permeation tests and potentiodynamic polarization curves have been used.

Addition of the inhibitor below the critical micelle concentration (CMC) decreased the corrosion current density (i_corr), but not enough to avoid embrittlement due to the entry of hydrogen into the steel. Instead, the addition of the inhibitor close to the CMC decreased the i_corr, suppressed the entry of hydrogen and inhibited the sulfide stress cracking of steel. Finally, the addition of inhibitor above the CMC led to a slight increase of i_corr and promoted localized corrosion, however, the sulfide stress cracking of steel was inhibited.

A green sulfide stress corrosion cracking inhibitor of a supermartensitic stainless steel has been obtained.

The purpose of this paper is to present a numerical simulation of the hydrogen atomic effect on the steels fracture toughness, as well as on crack propagation using fracture mechanics and continuous damage mechanics models.

The simulation was performed in an idealized elastic specimen with an edge crack loaded in the tensile opening mode, in a plane strain state. In order to simulate the effect of hydrogen in the steel, the stress intensity factor ahead of the crack tip in the hydrogenated material was obtained. The damage model was applied to simulate the growth and crack propagation being considered only two damage components: a mechanical damage produced by a static load and a non‐mechanical damage produced by the hydrogen.

The simulation results showed that the changes in the stress field at the crack tip and the reduction in the time of growth and crack propagation due to hydrogen effect occur. These results showed a good correlation and consistency with macroscopic observations, providing a better understanding of the hydrogen embrittlement phenomenon in steels.

The paper attempts to link the concepts of the continuous damage and fracture mechanics to achieve a better approach in the representation of the physical phenomenon studied, in order to obtain a more accurate simulation of the processes involved.