Hydrogen Embrittlement Susceptibility Research Articles

Effect of Quenching Cooling Rate on Hydrogen Embrittlement of Precipitation-Hardened Martensitic Stainless Steels

Effect of Quenching Cooling Rate on Hydrogen Embrittlement of Precipitation-Hardened Martensitic Stainless Steels

Susceptibility of X17CrNi16-2 martensitic stainless steel to hydrogen embrittlement after conventional and deep cryogenic heat treatment

A low carbon/ high chromium martensitic stainless steel, X17CrNi16-2, was heat treated using two different hardening and tempering regimes (1050 °C/480 °C or 980 °C/600 °C) — promoting either a high strength or high toughness state, respectively − and further combined with deep cryogenic treatment (DCT) at −196 °C for 24 h. Over recent years DCT has been recognized as a promising technique to improve the properties of steel, predominantly with respect to its tensile strength, toughness and wear resistance. The influence of DCT on the hydrogen embrittlement resistance of martensitic stainless steel has not yet, however, been reported.A slow strain rate tensile test (SSRT) with simultaneous cathodic hydrogen charging was selected as the method to assess potential susceptibility to hydrogen embrittlement (HE). Relatively low-intensity hydrogen charging, utilizing a constant current density of 0.1 mA/cm2, in a non-corrosive, slightly alkaline buffer solution, led to a clear reduction in the ultimate tensile stress. This reduction, and therefore the HE susceptibility, was more pronounced in the steel with a higher strength (i.e. that subject to the 1050 °C/ 480 °C heat treatment condition). Furthermore, DCT did not appear to have any impact on the steel’s mechanical properties in the presence of hydrogen. Fractographic analysis showed clear evidence of HE in the hydrogen-charged specimens.This paper presents results of the SSRT tests and further fractography results, and discusses the impact of conventional and deep cryogenic treatment on HE susceptibility.

Unveiling the roles of initial phase constituents and phase metastability in hydrogen embrittlement of TRIP-assisted VCrCoFeNi medium-entropy alloys

Medium-entropy alloys (MEAs) that exhibit transformation-induced plasticity (TRIP) from face-centered cubic (FCC) to body-centered cubic (BCC) are considered promising for liquid hydrogen environments due to their remarkable cryogenic strength. Nonetheless, studies on hydrogen embrittlement (HE) in BCC-TRIP MEAs have not been conducted, although the TRIP effect and consequent BCC martensite usually deteriorate HE susceptibility. In these alloys, initial as-quenched martensite alters hydrogen diffusion and trap behavior, and deformation-induced martensitic transformation (DIMT) provides preferred crack propagation sites, which critically affects HE susceptibility. Therefore, this study aims to investigate the HE behavior of BCC-TRIP MEAs by designing four V10Cr10Co30Fe50–xNix (x = 0, 1, 2, and 3 at%) MEAs, adjusting both the initial phase constituent and phase metastability. A decreased Ni content leads to a reduced fraction and mechanical stability of FCC, which in turn increases HE susceptibility, as determined through electrochemical hydrogen pre-charging and slow-strain rate tests The permeation test and thermal desorption analysis reveal that the hydrogen diffusivity and content are affected by initial BCC fraction, interconnectivity of BCC, and refined FCC. As these initial phase constituents differ between the alloys with FCC- and BCC- dominant initial phase, microstructural factors affecting HE are unveiled discretely among these alloy groups by correlation of hydrogen-induced crack behavior with hydrogen diffusion and trap behavior. In alloys with an FCC-dominant initial phase, the initial BCC fraction and DIMT initiation rate emerge as critical factors, rather than the extent of DIMT. For BCC-dominant alloys, the primary contributor is an increase in the initial BCC fraction, rather than the extent or rate of DIMT. The unraveled roles of microstructural factors provide insights into designing HE-resistant BCC-TRIP MEAs.

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.

Change in Hydrogen Trapping Characteristics and Influence on Hydrogen Embrittlement Sensitivity in a Medium-Carbon, High-Strength Steel: The Effects of Heat Treatments.

Medium-carbon, high-strength steels are widely used in the field of hydrogen energy because of their good mechanical properties, and they can be readily tailored by heat treatment processes such as the normalizing-tempering (N&T) and quenching-tempering (Q&T) methods. The hydrogen embrittlement (HE) susceptibility of a medium-carbon, high-strength steel was investigated utilizing microstructural characterization with scanning electron microscopy (SEM), the electron backscatter diffraction (EBSD) technique, and transmission electron microscopy (TEM). A study was also conducted on the steel's hydrogen transport behavior as affected by the N&T and Q&T treatments. The steel contained more hydrogen traps, such as dislocations, grain boundaries, lath boundaries, and carbide interfaces, after the Q&T process, which was associated with a lower HE sensitivity when comparing the two treatments. In comparison, the N&T process produced larger-size and lesser-density carbides distributed along the grain boundaries, and this resulted in a relatively higher HE susceptibility, as revealed by the slow-strain-rate tensile (SSRT) tests of the hydrogen-charged steels and by the fractographic study of the fracture surface.

Hydrogen embrittlement susceptibility of AISI 4140 alloy-steel under cathodic protection and in H2S and CO2 environment

The susceptibility to hydrogen embrittlement (HE) of AISI 4140 steel when subjected to environments such as those found in offshore oil and gas fields is investigated. Hydrogen charging was carried out for 15 days using two different hydrogen sources, cathodic protection (CP) and corrosion in a saline solution containing high concentrations of H2S and CO2 (SC-sour corrosion). The steel specimens were austenitized at 850 °C, oil-quenched at ambient temperature, followed by tempering for 18 min at 350, 450, and 600 °C. The effect of tempering temperatures on hydrogen embrittlement susceptibility was also investigated. Tensile strength testing, scanning electron microscopy (SEM), and fractography analysis were used to correlate the HE with microstructural and environmental conditions. The results revealed that both hydrogen charging conditions increased the steel hardness and decreased ductility, with this effect being more pronounced at lower tempering temperatures and SC-hydrogen charging. Fracture surfaces of the steel tempered at 600 °C with hydrogen charged exhibited predominantly ductile behavior with the presence of dimples, while at 350 and 450 °C surface fractures showed cleavage facets as a consequence of brittle behavior. In general, the AISI 4140 steel hydrogen embrittlement index (%EI) was higher for hydrogen charging induced by SC compared to CP.

Comparison between slow strain rate test and constant load test on notched specimens for HSLA steels HE susceptibility evaluation

The assessment of hydrogen embrittlement (HE) susceptibility in high-strength steels, intended for use in subsea components that are exposed to cathodic protection for corrosion control, is of great importance. Therefore, the present study investigates the behavior of AISI 4340 steel with hardness of 32, 36 and 40 HRC. The investigation involves employing slow strain rate test (nSSRT) and constant load test (CLT) on notched specimens with three different notch root radii. These tests were carried out under two different levels of cathodic protection (−1100 and −950 mVAg|AgCl) in a 3.5 % wt NaCl aqueous solution. The outcomes from the tests on notched specimens were compared with the hydrostatic stress profile obtained through finite element analysis (FEA). Additionally, the post-test fracture surfaces were analyzed using scanning electron microscopy (SEM). The test results revealed a higher hydrogen embrittlement index (HEI) with increasing material hardness and the applied cathodic potential. Moreover, a smaller notch radius was associated with a higher HEI. A clear correlation was observed between HEI and the extent of intergranular fracture in the test samples. Furthermore, the results from the nSSRT tests were correlated with the threshold stress (σth) obtained from CLT. It was evident that a relationship of σth = 90 %σnSSRT_min could be employed for a faster determination of this parameter.

Effect of mechanical strength on the hydrogen embrittlement susceptibility and fracture behavior of a modified AISI 4130 steel

Effect of mechanical strength on the hydrogen embrittlement susceptibility and fracture behavior of a modified AISI 4130 steel

Effect of Mn alloying on the hydrogen-assisted cracking behavior in multiphase/duplex stainless steel

There remains debate on whether Mn is beneficial or detrimental to hydrogen embrittlement in stainless steel. In this work, a series of stainless steels were designed to study the change of hydrogen embrittlement sensitivity, crack propagation, and hydrogen trapping behaviors upon Mn addition. The results suggest that adding 4 wt.% Mn increased hydrogen embrittlement susceptibility, whereas adding 8 wt.% Mn decreased hydrogen embrittlement sensitivity. Forming banded α'-martensite through austenitic grain is the main reason for the increased hydrogen embrittlement sensitivity when adding 4 wt.% Mn, by adsorbing hydrogen, promoting crack initiation, and accelerating crack propagation.

Effect of electrochemical charging on the hydrogen embrittlement susceptibility of a low-alloyed tempered martensitic steel submitted to high internal pressure

The influence of hydrogen on the mechanical behavior of a quenched and tempered 42CrMo4 steel has been evaluated by means of high internal pressure fracture tests carried out on hydrogen precharged notched cylindrical specimens. The notched cylindrical specimens were precharged for 3 h time with 1.2 mA/cm2 in two different aqueous media: 1 M H2SO4 added with 0.25 g/l As2O3 and 3.5% of NaCl solution. Hydraulic fracture tests were performed at different ramps of pressure: 7000, 220, 80, 60 and 30 MPa/h, respectively. Hydrogen damage was more marked when the acid aqueous medium (1 M H2SO4 + 0.25 g/l As2O3) was employed. In this case, a higher hydrogen concentration was introduced, leading to hydrogen decohesion micromechanisms (HEDE) near the notched region, especially when tests were performed at 60 MPa/h. Hydrogen embrittlement susceptibility is discussed in terms of the microstructural singularities and the operative fracture micromechanisms observed in each case.

Sub-stoichiometry and vacancy structures in V/Nb carbide precipitates by cluster expansion and first-principles calculations

Carbide precipitates, particularly V/Nb carbides, play a vital role in modulating many properties, including strength, hardness, wear resistance and hydrogen embrittlement (HE) susceptibility of steels. Our work presented a comprehensive study employing a cluster expansion (CE) approach combined with first-principles calculations to investigate the sub-stoichiometry induced by C vacancies within V/Nb carbides, an important aspect lacking sufficient understanding. Ground-state sub-stoichiometric V/Nb carbide compounds as the C composition varies were predicted, consistent with experimental observations. The predictions were further supported by the good agreement between the calculated bulk moduli and experimental measurements. The elastic moduli of carbides were shown to monotonically decrease as the C composition decreases, attributed to pd bonds being replaced by dd bonds with the introduction of vacancies. We have demonstrated that C vacancies in the carbides would arrange into particular patterns, with notable preference to form 3NN vacancy pairs and triplets. Such vacancy pattern formation was elucidated to be mainly driven by the elastic interaction between vacancies. The present study provides critical new knowledge regarding sub-stoichiometry and vacancy structures in carbide precipitates in steels. The findings are critical for an accurate understanding of the structures and properties of carbides and offer essential inputs for engineering steels of enhanced performance.

Influence of Calcareous Deposits on Hydrogen Embrittlement Susceptibility of Q460 Steel.

Cathodic protection is widely used to protect structural steel from corrosion in marine environments. However, an inappropriate cathodic potential may lead to hydrogen embrittlement (HE). Therefore, this study investigates the relationship between cathodic protection potential, structure and composition of calcareous deposits, and hydrogen embrittlement susceptibility of Q460 steel. The slow strain rate test results and fracture analysis reveal that Q460 steel had the smallest HE susceptibility when covered with the calcareous deposits formed under -1.1 VSCE. The deposits have a relatively thin calcium-rich inner layer and a condensed magnesium-rich outer layer, which can significantly inhibit hydrogen entry. A sustained deposition reaction during slow strain rate testing (SSRT) in artificial seawater can also decrease the HE susceptibility of Q460 steel.

Hydrogen embrittlement of FeCrAl alloys: The significant role of Laves phase and AlN particles

The addition of Nb to FeCrAl alloy enhanced its mechanical properties owing to the precipitated-phase strengthening effect. However, the additive amount and its effect on hydrogen embrittlement (HE) susceptibility have to be evaluated before implementation, as the hydrogen produced by fission and corrosion in the reactor may affect its mechanical properties. Therefore, hydrogen pre-charged tensile bar specimens were tested, and the HE mechanism was investigated. The results demonstrate that though FeCrAl alloys show low HE susceptibility, the Nb-doped FeCrAl alloys still exhibit a slightly higher HE susceptibility than Nb-free FeCrAl alloys. Their reduced ductility was mainly caused by decohesion and cracking of Fe2(Nb, Mo) precipitates and quasi-cleavage cracking induced by AlN inclusions. The underlying HE mechanisms for the Nb-doped FeCrAl alloys are hydrogen-enhanced localized plasticity (HELP) and HELP-mediated hydrogen-enhanced decohesion (HEDE).

Effect of Microalloying of V, Nb and Mo on Hydrogen Embrittlement Susceptibility of 2 GPa-grade Medium-carbon Si–Cr Spring Steel with Tempered Martensite Microstructure

Effect of Microalloying of V, Nb and Mo on Hydrogen Embrittlement Susceptibility of 2 GPa-grade Medium-carbon Si–Cr Spring Steel with Tempered Martensite Microstructure

Correlation between in-Situ small punch and conventional test result in evaluating hydrogen embrittlement susceptibility of API X70 base and weld under hydrogen gas mixture

The presence of microstructural heterogeneity within welded joints, combined with environmental factors, can have detrimental effects on the service life of engineering structural components. This study explores the effect of hydrogen/methane (H2/CH4) gas mixture under various volume fractions of hydrogen on the deformation and fracture behavior of a welded API X70 pipeline material employing the small punch test method. The welded metal showed more vulnerable to hydrogen-assisted fracture in comparison to the base metal, as evinced by a notable reduction in the volume fraction of hydrogen required for the transition from ductile to brittle behavior. The hydrogen embrittlement indexes obtained through the small punch test method are more severe than those obtained through conventional test methods. The direct utilization of small punch test results for the assessment of hydrogen compatibility in structural materials may yield overly conservative estimations. Quantitative parameters derived from the small punch test of both materials, along with fracture morphologies, were analyzed to establish a correlation between the hydrogen embrittlement indexes obtained through the small punch test and those obtained through conventional test methods. The small punch test method appears capable of detecting hydrogen embrittlement sensitivity resulting from adverse microstructural features existing in the metal matrix.

Establishing industrial Zn‑Ni brush electroplating process without post-plating hydrogen embrittlement relief baking

Transitioning from carcinogenic cadmium (Cd) to zinc‑nickel (Zn‑Ni) coating in aircraft components to prevent corrosion poses a challenge of hydrogen embrittlement (HE) of the substrate. While post-plating baking addresses HE in Zn‑Ni coated components, the economic repair of damaged coatings using the Zn‑Ni brush plating process without baking remains problematic. Therefore, in this work, the HE susceptibility of Zn‑Ni brush electroplating, both with and without baking has been investigated by subjecting plated notched specimens to a sustained load test (SLT) in accordance with ASTM F519. Baked specimens after plating passed the SLT, while unbaked specimens exhibit severe HE and fail. Adjusting electroplating parameters alone, such as plating current density and total plating electric charge, did not reduce HE vulnerability of the Zn‑Ni brush plating process without baking. However, optimizing the pre-plating grit blasting process (pressure, working distance), along with reducing the total plating electric charge, and introducing a 72 h delay between electroplating and subsequent SLT, enable plated specimens to exhibit no HE and to pass SLT without requiring baking.

Hydrogen Embrittlement Susceptibility of Linear Friction Welded Medium Carbon Steel Joints

Hydrogen Embrittlement Susceptibility of Linear Friction Welded Medium Carbon Steel Joints

Hydrogen Diffusion and Trapping Behaviour in DP Steels: An Electrochemical Hydrogen Permeation Study

Advanced high-strength steels (AHSSs) are widely used in the automotive industry as they possess high strength-to-weight ratio. This allows designing light vehicles with better passenger safety, lower fuel consumption, and CO2emissions. Dual-phase (DP) steels are very attractive among the AHSSs because of their optimal combination of high tensile strength (up to 1.2 GPa), high ductility (10 % or more), and good formability due to their two-phase microstructure (ferrite and martensite). However, the use of DP steel is associated with an increased risk of mechanical degradation in the presence of hydrogen environment, i.e., hydrogen embrittlement (HE). The HE susceptibility of DP steel is mainly determined by hydrogen entry, diffusion, and trapping events in the microstructure (i.e., hydrogen interaction with metal). There are various methods to study the above mechanism in metals like hydrogen charging-tensile test, thermal desorption spectroscopy, silver decoration, scanning kelvin probe microscopy, electrochemical hydrogen permeation, etc. Among these, electrochemical hydrogen permeation using Devanathan - Stachurski (DS) cell is a simple and most widely used technique.In this work, electrochemical hydrogen permeation was used to understand the role of microstructural features on hydrogen diffusion and trapping behaviour in DP-980 steel. It was identified that the phase fraction and its morphological features influence the hydrogen diffusion behaviour. The challenges in layout, design and integration of conventional DS cell into a tensometer and the effect of pre-strain (ex-situ) and tensile stress (in-situ) loading on hydrogen diffusion and trapping in DP-980 will be discussed. The applied elastic stress (i.e., 50 % of YS) during the permeation test resulted in a slight increase in Dapp from 5.4 ± 0.1 × 10- 7 to 5.9 ± 0.69×10-7 cm2s-1 and a slight reduction in NT from 1.08 ± 0.01 × 1021 to 1.0 ± 0.13× 1021 sites cm-3 compared to the no-stress condition. At 110 % of YS, the highest value of iss is 169 ±10.6 (µAcm-2) and a significant increase in the value of Capp to 3.6 ± 0.3 × 10-4 (molHcm-3 ), whereas no significant change in values of Dapp and NT were observed at 110 % YS compared to no stress and 50 % of YS. This could be due to the elastic deformation of martensite at 110 % of YS. The lattice expansion of martensite under elastic tensile stress can accommodate more interstitial hydrogen, thereby higher steady-state permeation current is observed. At 125 % of YS, the value of Dapp (2.86×10-7 cm2s-1) is approximately 50 % less compared to the value observed for the un-stressed specimen (5.4 ± 0.1×10-7 cm2s- 1). The value of NT (2.11×1021 cm-3) is approximately two times higher than that of the value (1.08×1021 cm-3 ). Plastic deformation of both ferrite and martensite results in increased dislocation density (hydrogen trap sites) at 125 % of YS. The sample failed during the hydrogen permeation test and when it is subjected to 125 % YS. It exhibited distinct fractographic features along the thickness of the sample. Quasi-cleavage and intergranular cracks were observed near the cathodic surface. Whereas, dimples and microvoids which are complete ductile features, were observed near the anodic surface. At 125 % of YS a significant decrease in the value of DL 0.6×10-6 cm2s-1 was observed. Whereas the value of NTrev increased to 4.0 ± 0.2×1019 cm-3 from 3.0 ± 0.15×1019 cm-3.An attempt was made to study the hydrogen transport behaviour at the local spot by appropriate modification of conventional DS cell. The fabrication challenges and the potential application of such an instrument will be elucidated.

Effect of microstructure on hydrogen embrittlement and hydrogen-induced cracking behaviour of a high-strength pipeline steel weldment

Hydrogen embrittlement (HE) and hydrogen-induced cracking (HIC) behaviour of a X65 steel pipeline weldment were investigated using slow strain rate tensile (SSRT) testing of specimens that were specifically extracted from different zones of the weldment (i.e., weld metal (WM), heat-affected zone (HAZ), and base metal (BM)). The WM was found to be the most susceptible zone to HE and HIC, while BM the least. Analysis of microstructure, fracture surface, secondary crack formation, and mechanical behaviour revealed that the high HE susceptibility of WM is correlated to microstructural features including Ti-rich inclusions, martensite/austenite (M/A) constituents, and prior austenite grain boundaries (PAGBs).

A strategy for simultaneously enhancing mechanical strength and hydrogen embrittlement resistance: Exceptional performance of laminated metal composite in hydrogen environments

High-strength metallic materials with low hydrogen embrittlement (HE) susceptibility have always been regarded as ideal commercial materials in the hydrogen energy field. This work proposed a low-cost laminated metal composite (LMC-CS) consisting of austenitic stainless steel (ASS) layer and martensitic steel (MART) layer, which simultaneously achieved high mechanical strength with excellent HE resistance. The ASS layers provide additional strain-hardening capability and the MART layer contributes high strength to LMC-CS after H-charging. Additionally, the composite interface displays semi-coherent characteristics, and the atomic arrangement on both sides follows the Kurdjumov-Sachs orientation relationship with (11¯0)α-Fe // (1¯11¯)γ-Fe and [111]α-Fe // [110]γ-Fe and the Nishiyama–Wassermann orientation relationship with (1¯1¯0)α-Fe // (1¯11)γ-Fe and [001]α-Fe // [011¯]γ-Fe., which coordinates deformation between layers and hinders hydrogen-induced cracks initiation at the interface. The as-designed LMC-CS achieves an ultimate tensile strength of 1102 MPa and an elongation loss of 14.8% after long-time hydrogen charging with sides sealed, outperforming a wide range of metallic materials. This work provides a fresh perspective on developing commercial materials with high strength and superior HE resistance for application in severe hydrogen environments.