Hydrogen Embrittlement Behavior Research Articles

Enhanced hydrogen embrittlement resistance of additive manufacturing Ti-6Al-4V alloy with basket weave structure

The hydrogen embrittlement (HE) behavior of tungsten inert gas arc additive manufacturing (AM) Ti-6Al-4V alloy was studied through tensile tests with/without hydrogen charging. The influence of hydrogen on the microstructure and crack propagation of AM Ti-6Al-4V alloy was investigated. The results indicated that the AM Ti-6Al-4V alloy with a basket weave structure alleviated local stress at grain boundaries during deformation, thus avoiding intergranular cracking and brittle fracture. The AM alloy displayed less HE susceptibility than that of the wrought alloy, which was due to the basket weave structure hindering the propagation of hydrogen-induced cracks, thereby improving the HE resistance.

Influence of Nb on the hydrogen-assisted cracking behaviour in multiphase stainless steel: Phase fractions, stacking fault energies, and nanosized NbC precipitation

Nb alloying has been reported to deteriorate the hydrogen embrittlement resistance of multiphase steels, which contrasts to the case of single-phase metallic materials. This study clarifies the impact of Nb alloying on the hydrogen embrittlement behaviour of a novel multiphase stainless steel. The findings revealed a 17 % reduction in the hydrogen embrittlement sensitivity upon Nb incorporation. It was found that higher austenite fractions in the Nb-bearing steels impeded hydrogen ingress. The austenite phase in such Nb-bearing steels possesses a higher stacking fault energy, thereby delaying martensitic transformation and crack initiation. The precipitation of nanometre-sized NbC in the matrix obstructed hydrogen diffusion, which indirectly inhibited crack initiation and propagation.

Effect of heat treatment on hydrogen embrittlement susceptibility of Al0.25CoCrFeNi high entropy alloy

In this study, the influences of annealing and aging treatments on the hydrogen embrittlement (HE) behavior of the cryo-rolled Al0.25CoCrFeNi high entropy alloy (HEA) were investigated through tensile tests and electrochemical hydrogen charging experiments. The results found that the aged sample showed high strength but was more susceptible to HE. A trade-off between the strength and HE resistance was achieved in the annealed + aged sample. Electron backscatter diffraction analysis and fracture characteristics were performed to clarify the HE mechanism. The high dislocation density and aggregated second phase along the grain boundaries in the aged sample were the important factors to help the initiation of HE crack, and then increasing the HE susceptibility. The annealed + aged sample with low dislocation density and aging precipitation reduced the risk of hydrogen-induced cracking and resulting in the excellent HE resistance. This work offered the method to obtain a comprehensive improvement in the strength and HE resistance of this alloy.

The Impact of Impurity Gases on the Hydrogen Embrittlement Behavior of Pipeline Steel in High-Pressure H2 Environments.

The use of hydrogen-blended natural gas presents an efficacious pathway toward the rapid, large-scale implementation of hydrogen energy, with pipeline transportation being the principal method of conveyance. However, pipeline materials are susceptible to hydrogen embrittlement in high-pressure hydrogen environments. Natural gas contains various impurity gases that can either exacerbate or mitigate sensitivity to hydrogen embrittlement. In this study, we analyzed the mechanisms through which multiple impurity gases could affect the hydrogen embrittlement behavior of pipeline steel. We examined the effects of O2 and CO2 on the hydrogen embrittlement behavior of L360 pipeline steel through a series of fatigue crack growth tests conducted in various environments. We analyzed the fracture surfaces and assessed the fracture mechanisms involved. We discovered that CO2 promoted the hydrogen embrittlement of the material, whereas O2 inhibited it. O2 mitigated the enhancing effect of CO2 when both gases were mixed with hydrogen. As the fatigue crack growth rate increased, the influence of impurity gases on the hydrogen embrittlement of the material diminished.

Effects of lattice misfit of γ/γ′ phases on hydrogen embrittlement behavior in Ni-based single crystal superalloy

The effect of γ/γ′ phase lattice misfit on hydrogen embrittlement (HE) behavior was fundamentally investigated by utilizing a Ni-based single crystal CMSX-4 superalloy with a simple microstructure that can exclude the H-trapping effects of grain boundary, c-vacancy, and misfit dislocation. Increasing isothermal aging time increased γ′ precipitate size while maintaining its volume fraction and a fully coherent interface. The magnitude of negative lattice misfit between the γ and γ′ phases increased from −0.08 to −0.22% according to γ′ precipitate coarsening, resulting in a well-developed tensile-strain field within the γ′ precipitate. The increased tensile-strain field enhanced activation energy for H-desorption in the γ′ precipitate from 31.9 to 35.1 kJ/mol. Therefore, H is preferentially distributed along the γ/γ′ interface within the γ′ precipitate even before deformation. H basically promotes the slip planarity through the H-enhanced localized plasticity (HELP) mechanism in Ni-based single crystal alloys, in which slip is the dominant deformation behavior. As the superalloy possesses a larger negative lattice misfit, H becomes trapped as diffusible-state at the tensile-strain field of the γ/γ′ interface, resulting in cuboidal brittle fracture along the {001} planes. In this process, the HELP mechanism facilitated H localization at the γ/γ′ interface. Thus, the HE behavior distinctly transitioned from HELP to an interaction between HELP and H-enhanced decohesion mechanisms (HEDE) with an increase in the magnitude of the lattice misfit. The HE behavior was investigated by correlating microstructural characterization, H-trapping behavior, and crystallographic fracture mechanism analysis.

Correlation between pre-strain and hydrogen embrittlement behavior in medium-Mn steel

In this study, we investigated the correlation between the pre-strain and hydrogen embrittlement (HE) mechanisms in medium-Mn steel. Intercritically annealed Fe-7Mn-0.2C-3Al (wt.%) steel, which showed a two-phase microstructure comprising α ferrite and γR retained austenite, was used as a model alloy. As the pre-strain level increased from 0 % to 45 %, the volume fraction of γR gradually decreased owing to the strain-induced α′ martensite transformation accompanied by an increase in dislocation density. The HE resistance decreased with increasing the pre-strain level because the sample with a higher pre-strain level revealed a higher amount of dissolved hydrogen, combined with a more extensive brittle fracture region owing to the enhanced diffusion and permeation of hydrogen from the reduced γR fraction. Additionally, the H-assisted crack in the sample without pre-strain was initiated and propagated from the γR grains when the strain-induced α′ phase was formed, because most of the dissolved hydrogen was concentrated in the γR grains, and these grains were predominantly deformed compared to the other phases. However, the pre-strained sample showed more pronounced multiple H-assisted cracking at the constituent phases, such as α and α′, because it exhibited relatively well-dispersed hydrogen atoms and reduced microstrain localization at the γR grains, due to the reduced γR fraction.

Investigation of Hydrogen Embrittlement of Haynes 617 and Hastelloy X Alloys Using Electrochemical Hydrogen Charging

This study explores the hydrogen embrittlement behaviour of two Ni-based superalloys using electrochemical hydrogen charging. Two types of tensile specimens with different geometry for the Haynes 617 and Hastelloy X alloys were electrochemically hydrogen-charged, and then a slow strain rate test was conducted to investigate the hydrogen embrittlement behaviour. Unlike the ASTM standard specimens, two-step dog-bone specimens with a higher surface-area-to-volume ratio showed higher sensitivity to hydrogen embrittlement because hydrogen atoms are distributed mostly on the surface area. On the other hand, the Haynes 617 alloy had a lower hydrogen embrittlement resistance than that of the Hastelloy X alloy due to its relatively large grain size and the presence of precipitates at grain boundaries. The Haynes 617 alloy primarily showed an intergranular fracture mode with cracks from the slip band, whereas the Hastelloy X alloy exhibited a combination of transgranular and intergranular fracture behavior under hydrogen-charged conditions.

Hydrogen embrittlement behaviors during SSRT tests in gaseous hydrogen for cold-worked type 316 austenitic stainless steel and iron-based superalloy A286 used in hydrogen refueling station

To consider an appropriate evaluation method for hydrogen compatibility, slow strain rate tensile (SSRT) tests were conducted on high strength piping materials, cold-worked type 316 austenitic stainless steel (SUS316CW) and iron-based superalloy A286, used in hydrogen stations for two years.SUS316CW, used at room temperature in 82 MPa gaseous hydrogen, contained 7.8 mass ppm hydrogen. The SSRT test of SUS316CW was conducted in nitrogen at −40 °C. The fracture surface showed dimples, and no hydrogen embrittlement behavior was observed. While, the SSRT test of SUS316CW in 70 MPa gaseous hydrogen at −40 °C showed a slight decrease in reduction area and a brittle fracture morphology in the outer layer. This was considered to be the effect of high-pressure gaseous hydrogen during the SSRT test in addition to the pre-contained hydrogen.A286, used at −40 °C in 82 MPa gaseous hydrogen, contained negligible hydrogen (0.14 mass ppm). SSRT tests were conducted at 150 °C in 70 MPa gaseous hydrogen and in air, and showed a low relative reduction in area (RRA) value. To investigate the decrease in the RRA, we switched the gas from hydrogen to air in the middle of the SSRT test and closely examined the RRA values and fracture morphology including side cracks. The hydrogen embrittlement was found to originate from the elastic deformation region. Stress cycling in the elastic deformation region also accelerated the effect of hydrogen. These were attributed to an increase in the lattice hydrogen content. While in the plastic deformation region, hydrogen trapped in the defects and hydrogen through the generated surface cracks increased the hydrogen content at the crack tips, reducing the RRA value. And there was a good correlation between the crack lengths and RRA values.Then, hydrogen embrittlement mechanism depends on the operating conditions (stress and temperature) of the material, and evaluating the hydrogen compatibility of materials by controlling their hydrogen content and strain according to the service environment is desirable.

Investigation into hydrogen assisted fracture in Nickel oligocrystals

This study investigates the hydrogen embrittlement (HE) behavior of Nickel-201 alloy using the oligocrystal approach. To comprehend the influence of microstructure toward HE, various types of tensile oligocrystals (True-oligocrystals, Quasi-oligocrystals, Identical-oligocrystals, and Bi-crystal type oligocrystals) with diverse microstructure (in terms of Schmid factor distribution and grain boundary types) are generated using a combination of heat treatment and slicing method. The electron backscatter diffraction (EBSD) analysis is used to validate the development of the desired tensile oligocrystal samples. Identical oligocrystal samples established the transition in fracture mode from ductile transgranular (TG) to brittle intergranular (IG), solely driven by hydrogen uptake. Post-tensile deformation analysis validated the hydrogen-induced IG fracture initiation and propagation along the random high-angle grain boundaries (RHAGBs) only. Bi-crystal type oligocrystals with low angle grain boundaries (LAGBs) and coincident-site lattice (CSL) Σ3 grain boundaries exhibited resistance to hydrogen-induced intergranular fracture, thus establishing the ‘special’ nature of these grain boundaries against the HE under current testing conditions.

Effect of plastic strain on corrosion-induced hydrogen infusion and embrittlement behaviors of Zn-coated ultra-high strength steel sheet

This study examined the effects of plastic strain on the corrosion-induced hydrogen evolution, infusion, and embrittlement behaviors of ultra-high strength steel sheets with galvanized (GI) and galvannealed (GA) coatings. The tensile pre-straining of the coated steels did not increase the hydrogen permeation flux in the absence of applied cathodic polarization, in contrast to the case under cathodic polarization. This was closely associated with the rapid kinetics of corrosion scale formation under pre-strains, providing an inhibitory effect on the surface. From this aspect, the difference in the resistance to corrosion-induced hydrogen embrittlement between GI and GA-coated steels was mechanistically interpreted.

Correlational research of microstructure characteristics and hydrogen induced cracking in hot-rolled Fe-6Mn-0.2C-3Al steels

Two-type specimens with different microstructure e.g. A70 contains finer-grained ferrite and austenite, while abundant coarse ferrite is obtained in A30. The different response on hydrogen embrittlement behavior results from the fundamental differences of microstructure. The dominant role of hydrogen in A30 lies in its local plastic enhancement influence on coarse ferrite, which is the efficient diffusion path for hydrogen, and that in A70 consists in its decohesion effect on ferrite/austenite interfaces, due to the inherited hydrogen of the fresh martensite at interfaces. This work provides a vital insight for microstructural design to improve hydrogen embrittlement resistance for medium Mn steels.

Improved resistance to hydrogen embrittlement in the nugget zone of friction stir welded medium Mn steel via post-welding annealing

In this work, medium-Mn steel was friction stir welded and then intercritically annealed. Hydrogen diffusion and hydrogen embrittlement (HE) behavior in the nugget zone (NZ) were investigated. The as-welded NZ exhibited the highest HE index (HEI) of 79.2%, and hydrogen‑induced cracks propagated along the grain boundary, probably depending on grain boundary decohesion caused by H segregation. However, this condition was improved by post-welding annealing since fine lath reversed austenite, acting as a strong hydrogen trap, was introduced into the ferritic matrix, inhibiting the segregation of H to grain boundaries. Ultimately, the lowest HEI of 10.7% was obtained in the as-annealed NZ.

Exploring the hydrogen embrittlement behavior in nickel-economized austenitic stainless steel: Investigating the role of manganese in modifying hydrogen-induced crack mechanisms

The hydrogen embrittlement (HE) susceptibility in nickel-economized austenitic stainless steels (NEASSs) with varying manganese content was explored based on the statistical results of hydrogen-induced cracks (HICs) characterization after slow strain rate tensile (SSRT). With almost the same initial microstructure, manganese modifies the deformation patterns of NEASSs by adjusting stacking fault energy, which essentially influences the initiation and propagation mechanisms of HICs and eventually results in different brittle fracture modes. Additionally, different ways of HIC initiation and propagation caused significant differences in brittle-fracture areas and HICs lengths after SSRT tests, which resulted in great variations in HE susceptibility between NEASSs.

Hydrogen embrittlement behavior of two mining chain steels by slow strain rate test

Two mining chain steels 23MnNiMoCr5-4 and 0.3C0.2Si0.3Mn4.2(Cr+Ni+Mo) with tensile strengths of 1200 MPa and 1250 MPa, respectively, were employed to investigate their hydrogen embrittlement behaviors by slow strain rate tests combined with thermal desorption analyses. It is shown that at initial stage the fracture stress decreases linearly as the hydrogen content increases, and the turning points occur at hydrogen content of 1.2 wppm for 0.3C0.2Si0.3Mn4.2(Cr+Ni+Mo) and 0.26 wppm for 23MnNiMoCr5-4. The fractured surface observation suggests that the ratio of intergranular fracture area to quasi-cleavage area increases dramatically at the turning points. The maximum hydrogen contents resulting from the corrosive HCl solutions with pHs of 2 are approximately 0.6 wppm 0.3C0.2Si0.3Mn4.2(Cr+Ni+Mo) and 0.11 wppm for 23MnNiMoCr5-4, corresponding to the activation energies for hydrogen desorption are 21.57 kJ/mol and 14.53 kJ/mol, respectively.

The influence of L12 ordered precipitates on hydrogen embrittlement behavior in CoCrNi-based medium entropy alloys

The recently emerged multicomponent (or medium/high entropy) alloys have generated considerable excitement globally in the last 10 years because of their excellent mechanical and functional properties, particularly in terms of strength-ductility combinations that can surpass most other metallic materials. However, the achieved high strength level (above 1 GPa in many cases) fuels strong concerns about hydrogen embrittlement (HE). Detailed investigation in this field is still scarce, especially pertaining to the face-centered cubic medium entropy alloys (MEA) that are typically strengthened by ordered precipitates. Here, we unravel the effect of γ' (L12) ordered precipitates on H-induced damage behavior and the associated HE resistance in CoCrNi-based MEAs. Compared with the equi-molar CoCrNi MEA, the precipitation-hardened (CoCrNi)94Al3Ti3 MEA shows an enhanced HE resistance even at a higher strength level. Both alloys are fractured due to H-assisted intergranular cracking at the initial failure stage when loaded in the presence of H. The formation of intergranular cracks is primarily attributed to the H-induced decohesion at grain boundaries, where a high stress/strain concentration accompanied by a more intensive dislocation planar slip (or stacking fault formation) caused by H was observed. The presence of γ' precipitates serves to slow down the internal diffusion/migration of H due to the trapping effects. The precipitates with a relatively larger size (∼50 nm) also hinder dislocation planar slip thus decreasing the number of pile-up dislocations at grain boundaries. Both effects collectively reduce the tendency of H-induced intergranular cracking, leading to the improved HE resistance. The work reveals the positive role of ordered precipitates in H tolerance and thus provides some insights in further microstructure design of medium/high entropy alloys for applications in H-abundant environment.

Hydrogen embrittlement susceptibility of additively manufactured 316L stainless steel: Influence of post-processing, printing direction, temperature and pre-straining

The influence of post-build processing on the hydrogen embrittlement behavior of additively manufactured (AM) 316L stainless steel fabricated using laser powder bed fusion was assessed at both room temperature and −50 °C via uniaxial tensile experiments. In the absence of hydrogen at ambient temperature, all four evaluated AM conditions (as-built (AB), annealed (ANN), hot isostatic pressed (HIP), and HIP plus cold worked (CW) to 30%) exhibit notably reduced ductility relative to conventionally manufactured (CM) 316L stainless steel. The AM material exhibits sensitivity to the build direction, both in the presence and absence of hydrogen, with a notable increase in yield strength in the X direction and enhanced ductility in the Z direction. Conversely, testing of non-charged specimens at −50 °C revealed similar ductility between the CM, AB, ANN, and HIP conditions. Upon hydrogen charging, the ductility of all four AM conditions was found to be similar to that of CM 316L at ambient temperature, with the HIP condition actually exceeding the CM material. Critically, testing of hydrogen-charged samples at −50 °C revealed that the ductility of the HIP AM 316L condition was nearly double that observed in the CM 316L. This improved performance persisted even after cold working, as the CW AM 316L exhibited comparable ductility to CM 316L at −50 °C after hydrogen charging, despite having a 2-fold higher yield strength. Feritscope measurements suggest this increased performance is related to the reduced propensity for AM 316L to form strain-induced martensite during deformation, even after significant post-processing treatments. These results demonstrate that AM 316L can be post-processed using typical procedures to exhibit similar to or even improved resistance to hydrogen embrittlement relative to CM 316L.

Hydrogen Embrittlement Behavior and Mechanism of Low Carbon Medium Manganese Steel Gas Metal Arc Welding Joints

Hydrogen Embrittlement Behavior and Mechanism of Low Carbon Medium Manganese Steel Gas Metal Arc Welding Joints

Hydrogen Embrittlement Behavior of a Commercial QP980 Steel

The hydrogen embrittlement (HE) behavior of a commercial QP980 steel is studied in this work. The HE susceptibility results indicate that QP980 suffers from a severe HE, and the fracture mode transforms from ductile dimpling to brittle quasi-cleavage under the attack of hydrogen. The EBSD results show that strain-induced martensite transformation can rarely occur at a strain close to the HE fracture strain, which is mainly attributed to the high mechanical stability of austenite. The TKD-KAM analysis results indicate that hydrogen-induced strain localization in martensite can be mitigated by the hydrogen-trapping effect of surrounding austenite, while it is most pronounced in martensite adjacent to ferrite. Correspondingly, HE cracking is considered to initiate in martensite adjacent to ferrite under the synergistic action of HELP and HEDE mechanisms, and then cracks can propagate through ferrite or along phase interfaces. Our findings suggest that to further improve the HE resistance of QP steel with stable austenite, it is necessary to consider introducing effective hydrogen-trapping sites (such as carbides, film austenite) into martensite, which is deemed to be beneficial for increasing the resistance against hydrogen-induced cracking initiation in martensite.

Hydrogen-induced cracking of X70 steel affected by sulfate-reducing bacteria and cathodic potential: experiment and density functional theory study

Submarine pipeline are often exposed to the risk of hydrogen embrittlement from the dual action of marine sulfate-reducing bacteria (SRB) and cathodic protection (CP). In this work, hydrogen permeation test, slow strain rate tensile (SSRT) experiments, and density functional theory (DFT) were used to explain the hydrogen embrittlement (HE) mechanism of subsea pipeline steel under the action of SRB and CP. When the applied CP potential is increased from −850 mV to −1200 mV, the hydrogen seepage current increases 1.8 times. And the tensile specimens pre-charged with hydrogen exhibit significant hydrogen embrittlement behavior. DFT calculations show that the increased concentration of hydrogen atoms on the material surface decreases the diffusion potential barrier, leading to a larger hydrogen seepage current. In addition, the aggregation of hydrogen atoms in the steel weakens the chemical bonds between Fe atoms, leading to hydrogen embrittlement.

EFFECT OF SHOT PEENING DURATION ON FATIGUE LIFE OF GALVANIZED AND NON-GALVANIZED PEARLITIC HIGH STRENGTH HELICAL COMPRESSION SPRINGS

In this study, the effect of shot peening duration on the fatigue life of galvanized and non-galvanized springs was investigated. As the shot peening duration increased, the fatigue life of the compression springs decreased due to several embrittlement mechanisms on the spring surface. The surface roughness almost linearly increased with increasing shot peening durations. The best fatigue life was obtained with shot peening durations of 10 and 20 min for non-galvanized and galvanized springs, respectively. The non-galvanized specimens exhibited better fatigue performance than galvanized springs. The main reason for the decrease in the fatigue performance of galvanized springs is hydrogen embrittlement behavior. Free hydrogen generated in the acid bath during the galvanizing process is entrapped between the surface and the zinc layer. As a result, the compression strain that reflects crack onset and propagation was adversely affected by hydrogen embrittlement behavior.