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This paper aims to verify the inhibition of the hydrogen permeation effect of the coating and to quantitatively and qualitatively characterize the coating-induced stress.

By means of slow strain rate tensile testing (SSRT) in humid air, thickness measurement, fracture morphology, cross-section morphology and surface morphology, hydrogen content measurements, flow stress difference method.

The results demonstrate that the mechanism of the inhibition of hydrogen embrittlement by the coating is mainly attributed to the repression of hydrogen permeation and the additional coating-induced compressive stress.

It is proven that the micro-arc oxidation (MAO) coating does inhibit hydrogen entry into the alloy, and the stress induced by the MAO coating is compressive stress, which can restrain the hydrogen embrittlement of the alloy. Therefore, the mechanism of the inhibition of hydrogen embrittlement is dominated by the mechanisms of both hydrogen permeation inhibition and coating-induced stress.

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.

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.

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.

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.

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.

High-strength martensitic steels having strong hydrogen embrittlement (HE) susceptibility and the metal carbide (MC) nanoprecipitates of microalloying elements such as Nb, V, Ti and Mo in the steel matrix can effectively improve the HE resistance of steels. This paper aims to review the effect of MC nanoprecipitates on the HE resistance of high-strength martensitic steels.

In this paper, the effects of MC nanoprecipitates on the HE resistance of high-strength martensitic steels are systematically described in terms of the types of MC nanoprecipitates, the influencing factors, along with numerical simulations.

The MC nanoprecipitates, which are fine and semicoherent with the matrix, effectively improve the HE resistance of steel through the hydrogen trapping effects and microstructure optimization, but its effect on the HE resistance of steel is controlled by its size, number and distribution state.

This paper summarizes the effects and mechanisms of MC nanoprecipitates on HE performance of high-strength martensitic steel and provides the theoretical basis for corrosion engineers to design high-strength martensitic steels with excellent HE resistance and improve production processes.

Alternating current (AC) corrosion is a type of corrosion that occurs in buried pipelines under AC stray current interference, which can increase the hydrogen embrittlement sensitivity of pipelines. However, rare research works have been conducted on the hydrogen permeability characteristics of pipeline steel under AC stray current interference. The purpose of this paper is to study hydrogen permeation behavior of X80 steel under AC stray current interference.

In this paper, the hydrogen permeation behavior of X80 steel under AC interference is studied by AC hydrogen charging experiment in a dual electrolytic cell. The relationship between hydrogen evolution rate and hydrogen permeation flux is studied using the gas collection method. The difference between AC hydrogen permeability and direct current (DC) hydrogen permeability is also discussed.

The anodic dissolution caused by AC corrosion promotes the chemical desorption reaction of the adsorbed hydrogen atoms on the surface, reducing the hydrogen atom absorption ratio by 70%. When the AC is smaller than 150░ A/m², the hydrogen permeation process is controlled by the hydrogen atom generation rate, and the hydrogen permeation flux increases with the increase in hydrogen atom generation rate. When the AC exceeds 400░ A/m², the hydrogen permeation process is controlled by the absorption ratio. The hydrogen permeation flux decreases with the decrease in the absorption ratio. Under AC interference, there is a maximum hydrogen permeation flux that linearly correlates to the H⁺ concentration in the solutions.

The high-strength steel is very sensitive to hydrogen embrittlement, and X80 steel has been widely used in oil and gas pipelines. To date, no research has been conducted on the hydrogen permeation behavior of pipeline steel under AC interference, and the hydrogen permeability characteristics of pipeline steel under AC interference are not clear. The research results of this paper are of great significance for ensuring the intrinsic safety of high-strength pipelines under AC stray current interference.

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.

To make wind energy (one of the alternative-energy production technologies) economical, wind-turbines (convertors of wind energy into electrical energy) are required to operate, with only regular maintenance, for at least 20 years. However, some key wind-turbine components (especially the gear-box) often require significant repair or replacement after only three to five years in service. This causes an increase in both the wind-energy cost and the cost of ownership of the wind turbine. The paper aims to discuss these issues.

To overcome this problem, root causes of the gear-box premature failure are currently being investigated using mainly laboratory and field-test experimental approaches. As demonstrated in many industrial sectors (e.g. automotive, aerospace, etc.) advanced computational engineering methods and tools cannot only complement these experimental approaches but also provide additional insight into the problem at hand (and do so with a substantially shorter turn-around time). The present work demonstrates the use of a multi-length-scale computational approach which couples large-scale wind/rotor interactions with a gear-box dynamic response, enabling accurate determination of kinematics and kinetics within the gear-box bearings (the components most often responsible for the gear-box premature failure) and ultimately the structural response (including damage and failure) of the roller-bearing components (e.g. inner raceways).

It has been demonstrated that through the application of this approach, one can predict the expected life of the most failure-prone horizontal axis wind turbine gear-box bearing elements.

To the authors’ knowledge, the present work is the first multi-length-scale study of bearing failure in wind-turbines.