In situ electrochemical microcantilever bending test: A new insight into hydrogen enhanced cracking

Hajilou, Tarlan; Deng, Yun; Rogne, Bjørn Rune Sørås; Kheradmand, Nousha; Barnoush, Afrooz

doi:10.1016/j.scriptamat.2017.01.019

Cited by 87 publications

(36 citation statements)

References 29 publications

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“…This model fits very well with our observations. Another interesting idea was introduced recently by Hajilou et al [24]. The authors found similar plasticity suppression during the bending test using micro-sized cantilever of Fe-3%Si alloy under in-situ electrochemical hydrogen-charging.…”

Section: Dislocation Structures Characterized By Temmentioning

confidence: 83%

Hydrogen-assisted fatigue crack propagation in a pure BCC iron. Part II: Accelerated regime manifested by quasi-cleavage fracture at relatively high stress intensity range values

et al. 2018

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Abstract. Hydrogen effect on fatigue performance at relatively high values of stress intensity factor range, ΔK, of pure BCC iron has been studied with a combination of various electron microscopy techniques. Hydrogen-assisted fatigue crack growth rate is manifested by a change of fracture features at the fracture surface from ductile transgranular in air to quasi-cleavage in hydrogen gas. Grain reference orientation deviation (GROD) analysis has shown a dramatic suppression of plastic deformation around the crack wake in samples fatigued in hydrogen. These results were verified by preparing site-specific specimens from different fracture features by using Focused Ion Beam (FIB) technique and observing them with Transmission Electron Microscope (TEM). The FIB lamella taken from the sample fatigued in air was decorated with dislocation cell structure indicating high amount of plasticity, while the lamella taken from the quasi-cleavage surface of the sample fatigued in hydrogen revealed a distribution of dislocation tangles which corresponds to smaller plastic strain amplitude involved at the point of fracture. These results show that a combination of critical hydrogen concentration and critical stress during fatigue crack growth at high ΔK values triggers cleavage-like fracture due to reduction of cohesive force between matrix atoms.

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Section: Dislocation Structures Characterized By Temmentioning

confidence: 83%

Hydrogen-assisted fatigue crack propagation in a pure BCC iron. Part II: Accelerated regime manifested by quasi-cleavage fracture at relatively high stress intensity range values

et al. 2018

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“…In addition, the local H concentration, C σ , of the highly stressed regions in the DCB sample can be estimated using the following equation [46]:

C_{σ} = C_{0} e x p (σ_{h} V_{H} / R T)

where C 0 is the diffusion H concentration, σ h is the hydrostatic stress, V H is the partial molar volume of H in iron (2.1 × 10 −6 m 3 /mol), R is the gas constant and T is the ambient temperature. As this equation indicates, C σ decreased as the result of decreased C 0 .…”

Section: Discussionmentioning

confidence: 99%

Sulfide Stress Cracking Behavior of a Martensitic Steel Controlled by Tempering Temperature

Sun

Wang

et al. 2018

Materials

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A medium-carbon Cr–Mo–V martensitic steel was thermally processed by quenching (Q) at 890 °C and tempering (T) at increasing temperatures from 650 °C to 720 °C and the effect of tempering temperature, Tt, on sulfide stress cracking (SSC) behaviors was estimated mainly via double cantilever beam (DCB) and electrochemical hydrogen permeation (EHP) tests and microstructure characterization. The results indicate that the threshold stress intensity factor for SSC, KISSC, increased with increasing Tt. The overall and local H concentration around the inclusions decreased with increasing Tt, due to reductions in the amounts of solute atoms, grain boundaries and dislocations, which effectively prevented SSC initiation. Also, increasing Tt caused an increased fraction of high-angle boundaries, which evidently lowered the SSC propagation rate by more frequently diverting the propagating direction and accordingly restricted SSC propagation. The overall SSC resistance of this Q&T–treated steel was therefore significantly enhanced.

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“…GNDs are regarded as the fingerprint of deformation. [44][45] In TEM investigations these appear as the hotspots of strain localization in the material, typically known by cell or microband nomenclature. 46 Although, a comparison between the phase and KAM maps (Figures 9[b] and [d]) indicated that the GND boundaries, which arise due to deformation, were present in both phases, qualitatively, they seem to form predominantly within austenite.…”

Section: Fractographymentioning

confidence: 99%

Hydrogen-Induced Stress Cracking of Swaged Super Duplex Stainless Steel Subsea Components

et al. 2019

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A recent subsea failure of two subsea connectors made of UNS S32760, a 25 wt% Cr super duplex stainless steel, led to an extensive root cause failure analysis. The components showed a single longitudinal crack along a swaged section, which arrested toward its thicker end. The brittle nature of the fracture surface, calcareous deposits on the component, and exposure to cathodic protection suggested hydrogeninduced stress cracking-a form of environmentally assisted cracking-as a plausible failure mechanism. Thus, the three causative factors promoting hydrogen-induced stress cracking, namely, a susceptible microstructure, a hydrogen bearing environment, as well as sufficiently high applied and residual stresses in the material were the focus of this investigation. This work details the material characterization work and presents a possible failure mechanism. The results showed that the failure developed from a combination of factors, typical for hydrogeninduced stress cracking. The measured hydrogen content in parts of the material exceeded 40 ppm, more than an order of magnitude higher than what is normally expected in super duplex stainless steels. Additionally, a highly anisotropic, coarse microstructure was observed, which in combination with the introduced cold-work from the swaging process and potential stress raisers from design and machining could have facilitated crack initiation, ultimately leading to the failure of the component. This hypothesis was reinforced by the presence of secondary cracks along the main, brittle fracture surface. Furthermore, mechanical testing results showed a detrimental effect on the material's properties due to the presence of residual hydrogen and the swaging operation.

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In situ electrochemical microcantilever bending test: A new insight into hydrogen enhanced cracking

Cited by 87 publications

References 29 publications

Hydrogen-assisted fatigue crack propagation in a pure BCC iron. Part II: Accelerated regime manifested by quasi-cleavage fracture at relatively high stress intensity range values

Hydrogen-assisted fatigue crack propagation in a pure BCC iron. Part II: Accelerated regime manifested by quasi-cleavage fracture at relatively high stress intensity range values

Sulfide Stress Cracking Behavior of a Martensitic Steel Controlled by Tempering Temperature

Hydrogen-Induced Stress Cracking of Swaged Super Duplex Stainless Steel Subsea Components

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