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The susceptibility to hydrogen embrittlement behavior was investigated in an interstitial Mn–N austenitic steel HR183 and stainless steel 316L. Hydrogen was introduced by cathodic hydrogen charging at 363 K. HR183 has stronger austenite stability than 316L despite its lower nickel content, the addition of manganese and nitrogen inhibited martensitic transformation during the slow strain rate tensile deformation. Due to the diffusion of hydrogen being delayed by the interstitial solution of nitrogen atoms and the uniform dislocation slips, hydrogen permeates more slowly in HR183 than 316L, contributing to an 84.79 μm thinner brittle fracture layer in HR183 steel. Hydrogen charging caused elongation losses in both 316L and HR183 steels associated with the hydrogen-enhanced localized plasticity (HELP) and hydrogen-enhanced decohesion (HEDE) mechanism. However, the hydrogen embrittlement susceptibility of HR183 is 3.4 times lower than that of 316L according to the difference in elongation loss between the two steel after hydrogen charging. Deformation twins trapped a lot amount of hydrogen leading to brittle intergranular fracture in 316L. The multiple directions of slip in HR183 steel suppressed the strain localization inside grains and delayed the adverse effects conducted by HELP and HEDE mechanism, eventually inhibiting server hydrogen embrittlement in the HR183 steel. This study is assisting in the development of low-cost stainless steel with excellent hydrogen embrittlement resistance that can be used in harsh hydrogen-containing environments. [Display omitted] • SIM was suppressed by adding manganese and nitrogen with low nickel content. • Interstitial nitrogen affected the solubility of hydrogen in FCC lattice and slowed down the permeation of hydrogen. • The HELP and HEDE mechanism conducted hydrogen embrittlement in interstitial Mn–N austenitic steel. • Multiple directions of slip alleviated the adverse effect of HELP and HEDE mechanism. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • The hydrogen-induced cracking behavior in nickel-economized austenitic stainless steels is systematically explained. • A Higher Mn alloying leads to a lower strength/elongation loss in NEASSs. • The hydrogen embrittlement performance of NEASS is essentially influenced by its deformation mode during SSRT tests. • The fracture mode of the brittle-fracture zone is determined by the initiation and propagation behavior of HICs • For NEASSs with plastic deformation dominated by dislocation slip exhibit lower HE susceptibility. [ABSTRACT FROM AUTHOR]

[Display omitted] • A low-cost composite (LMC-CS) was designed, which simultaneously exhibited high strength and low HE susceptibility. • Austenitic layer blocks and absorbs the majority of hydrogen, maintaining ductile failure in LMC-CS after fracture. • Semi-coherent composite interface is generated inside DRX grains by the limited element diffusion. • The semi-coherent composite interface deeply trapped hydrogen, thereby hindering hydrogen-induced crack initiation. 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 (1 1 ¯ 0) α-Fe // ( 1 ¯ 1 1 ¯ ) γ-Fe and [1 1 1] α-Fe // [1 1 0] γ-Fe and the Nishiyama–Wassermann orientation relationship with ( 1 ¯ 1 ¯ 0) α-Fe // ( 1 ¯ 11) γ-Fe and [0 0 1] α-Fe // [ 01 1 ¯ ] 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. [ABSTRACT FROM AUTHOR]

Hydrogen-induced damage is an inevitable challenge in pipeline safety applications, especially, the fusion welded joints owing to microstructure heterogeneity caused by welding process. In this work, X100 pipeline steel was subjected to friction stir welding (FSW) at rotation rates of 300–600 rpm under water cooling, and the relationship among the microstructure, hydrogen diffusivity, and hydrogen embrittlement (HE) behavior of the nugget zone (NZ) were studied. The NZ at 600 rpm had the highest effective hydrogen diffusion coefficient (D eff) of 2.1 × 10−10 m2/s because of the highest dislocation density and lowest ratio of effective grain boundary. The D eff decreased with decreasing rotation rate due to the decrease of dislocation density and the increase of ratio of effective grain boundary, and the lowest D eff of 1.32 × 10−10 m2/s was obtained at 300 rpm. After hydrogen charging, the tensile strength of all specimens decreased slightly, while the elongation decreased significantly. As the rotation rate decreased, the elongation loss was obviously inhibited, and ultimately a lowest elongation loss of 31.8% was obtained at 300 rpm. The abovementioned excellent mechanical properties were attributed to the fine ferrite/martensite structure, low D eff , and strong {111}//ND texture dramatically inhibiting hydrogen-induced cracking initiation and propagation. • FSW of X100 steel was performed in water cooling, producing defect-free weld. • The diffusion behavior of hydrogen in the NZ was studies. • The effect of hydrogen on deformation and fracture behavior was analyzed. • The NZ with fine ferrite/martensite present high HE resistance. [ABSTRACT FROM AUTHOR]