Effect of hydrogen on the mechanical properties of alloy 945X (UNS N09945) and influence of microstructural features

Demetriou, Velissarios; Robson, James; Preuß, Michael; Morana, Roberto

doi:10.1016/j.msea.2016.12.088

Cited by 29 publications

(8 citation statements)

References 24 publications

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“…To explain the effect of hydrogen on this phenomenon, a hydrogen-enhanced strain-induced void (HESIV) mechanism was suggested, which was observed in our previous study [17]. According to the HESIV theory, voids can be easily formed by the hydrogen at the intersections of hydrogen trapping sites such as carbide interfaces, lath boundaries, and dislocations [17,36,37]. To analyse the causes of the IG fracture and stair morphology observed in the HSC fracture surface (Figure 7), the FE-TEM images of the fracture surfaces were extracted using FIB, as shown in Figure 10a,b.…”

Section: Effect Of Type-ii Boundary Microstructure On the Hsc Behaviour Of The Wjsmentioning

confidence: 97%

Hydrogen Stress Cracking Behaviour in Dissimilar Welded Joints of Duplex Stainless Steel and Carbon Steel

Park

Moon

et al. 2021

Metals

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As the need for duplex stainless steel (DSS) increases, it is necessary to evaluate hydrogen stress cracking (HSC) in dissimilar welded joints (WJs) of DSS and carbon steel. This study aims to investigate the effect of the weld microstructure on the HSC behaviour of dissimilar gas-tungsten arc welds of DSS and carbon steel. In situ slow-strain rate testing (SSRT) with hydrogen charging was conducted for transverse WJs, which fractured in the softened heat-affected zone of the carbon steel under hydrogen-free conditions. However, HSC occurred at the martensite band and the interface of the austenite and martensite bands in the type-II boundary. The band acted as an HSC initiation site because of the presence of a large amount of trapped hydrogen and a high strain concentration during the SSRT with hydrogen charging. Even though some weld microstructures such as the austenite and martensite bands in type-II boundaries were harmless under normal hydrogen-free conditions, they had a negative effect in a hydrogen atmosphere, resulting in the premature rupture of the weld. Eventually, a premature fracture occurred during the in situ SSRT in the type-II boundary because of the hydrogen-enhanced strain-induced void (HESIV) and hydrogen-enhanced localised plasticity (HELP) mechanisms.

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Section: Effect Of Type-ii Boundary Microstructure On the Hsc Behaviour Of The Wjsmentioning

confidence: 97%

Hydrogen Stress Cracking Behaviour in Dissimilar Welded Joints of Duplex Stainless Steel and Carbon Steel

Park

Moon

et al. 2021

Metals

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“…The calculated hydrogen concentration ratio terminates at different points, corresponding to a variation in samples' thickness. Obviously, a steep concentration gradient is generated along the sample, which is a common feature in FCC metals during cathodic charging [30,53,54]. In this alloy, the aging process annealed out most of the internal stress induced by water quenching, and electropolishing before hydrogen charging guaranteed the surfaces free from residual stresses.…”

Section: Pre-damages Induced By Cathodic Chargingmentioning

confidence: 99%

“…Hydrogen-assisted intergranular cracking was observed in the precipitation hardened nickel-based superalloys. Different from the debonding mechanism proposed for intergranular cracking in the presence of  phase [28,30,53], in this study, we introduced a new parameter, i.e. GB resistance to slip transmission, to understand the stress incompatibility between the adjacent grains and its impact on the propensity for GB cracking.…”

Section: Hydrogen-assisted Intergranular Cracking During Deformationmentioning

confidence: 99%

Effect of electrochemical charging on the hydrogen embrittlement susceptibility of alloy 718

Wang

Wan

et al. 2019

Acta Materialia

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The susceptibility of age-hardened nickel-based 718 superalloy to hydrogen embrittlement was studied by the controlled electrochemical charging combined with slow strain-rate tensile tests (SSRT) and advanced characterization techniques. We proposed some novel ideas of explaining hydrogen embrittlement mechanisms of the studied material in regard to two cracking morphologies: transgranular and intergranular cracking. It is for the first time to report that electrochemical charging alone could cause slip lines, surface and subsurface cracks on nickel-based superalloys. The formation of pre-damages was discussed by calculating the hydrogen concentration gradient generated during cathodic charging. Predamages were proved to result in transgranular cracks and lead to the evident reduction of mechanical properties. In addition, the STRONG (Slip Transfer Resistance of *Manuscript_clean Click here to download Manuscript: Revised Manuscript_clean_A-19-1789_R1.docx Click here to view linked References Neighbouring Grains) model was used to analyze the dependence of hydrogen-assisted intergranular cracking on the microscopic incompatibility of the grain boundaries. The results show that in the presence of hydrogen, grain boundaries with a lower dislocation slip transmission are more prone to cracking during loading and vice versa.

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“…In contrast, for the HEDE mechanism cracking occurs as a consequence of the reduction in the cohesive strength of the lattice under the influence of hydrogen. This mechanism for nickel alloys is reported to take place at grain boundaries frequently associated with δ-phase precipitation [7,[10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Hydrogen embrittlement of single-phase strain-hardened nickel-based UNS N08830 alloy

Burille

Scheid

Ferreira

et al. 2021

Materials Science and Engineering: A

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This work evaluated the hydrogen embrittlement resistance of the nickel-based UNS N08830 alloy through a hydrogen charging study, slow strain rate (SSR), and fracture toughness tests. The microstructure evaluation showed large-size austenitic grains with no evidence of second phase precipitation, a high fraction of low-angle grain boundaries, and texture of {100} and {111} planes in the rolling direction. From SSR tests results, strain to fracture and reduction of area embrittlement indexes of 25.3 and 42.1% were found, respectively. A modest drop in fracture toughness of approximately 20% was observed. From fractography, it was observed a prevailing mixed micromechanism of fracture comprised of microvoids coalescence and quasi-cleavage flat facets in secondary cracks aligned with the rolling direction. The quasi-cleavage flat facets showed nanovoids at the slip line intersections, which in turn confirmed Hydrogen-Enhanced Localized Plasticity (HELP) as the prominent embrittlement mechanism. Because of the material's crystallographic texture, a good part of hydrogen was not transported to a direction normal to the applied stress as it would happen for pure diffusion but instead followed the dislocations in the rolling direction. That effect caused that less hydrogen was concentrated in the main crack tip, which inevitably increased the overall energy for fracture.

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Effect of hydrogen on the mechanical properties of alloy 945X (UNS N09945) and influence of microstructural features

Cited by 29 publications

References 24 publications

Hydrogen Stress Cracking Behaviour in Dissimilar Welded Joints of Duplex Stainless Steel and Carbon Steel

Hydrogen Stress Cracking Behaviour in Dissimilar Welded Joints of Duplex Stainless Steel and Carbon Steel

Effect of electrochemical charging on the hydrogen embrittlement susceptibility of alloy 718

Hydrogen embrittlement of single-phase strain-hardened nickel-based UNS N08830 alloy

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