Stress Corrosion Crack Propagation Research Articles

Effect of cold work level on the crack propagation behaviour of 316LN stainless steel in high-temperature pressurized water

We investigated the microstructure, mechanical properties, and stress corrosion cracking (SCC) propagation behaviour of 316LN austenitic stainless steel with various cold work (CW) levels. CW increased the crack growth rate of 316LN. The stress corrosion crack growth rate (SCCGR) for 316LN with 5% CW was approximately 6.52% higher than that of the solution-annealed state; 10%, 20%, and 30% CW resulted in 1.20, 3.18, and 6.10 times higher SCCGRs, respectively. A larger residual strain and proliferation of slip bands via cold deformation augmented the SCCGR. The SCC propagation mechanism of 316LN changed with increasing CW levels owing to slip bands.

Revealing the environmental-assisted degeneration mechanism of an Al-containing dual-phase high entropy alloy in supercritical water

A dual-phase high entropy alloy (DP-HEA) containing 7.82 wt% Al was synthesized to withstand corrosive supercritical water. The long-term corrosion and quasi-static tensile tests reveal superior resistance to such environmental-assisted degeneration. The outstanding corrosion resistance can be attributed to the high aluminum content in B2 phase, which forms a continuous Al2O3 layer for protection, while the FCC phase is selectively corroded. Under external stress, stress corrosion cracking (SCC) initiates from surface oxide and penetrates uncompact mixed Cr/Al-rich oxide in deteriorated FCC regions or corroded phase interface, though network-shaped B2 can inhibit SCC propagation, which supports the brittle film rupture model.

A phase‐field framework for stress corrosion cracking prediction in elastoplastic metallic materials

AbstractTo capture the stress corrosion cracking (SCC) in metallic materials, a phase‐field framework considering localized plastic deformation and stress states is established. A new function of critical energy release rate is proposed to describe the degradation of cracking resistance of materials in the SCC process. This proposed framework can reproduce SCC results consistent with experimental observations in C‐ring steel SCC tests, especially capturing the directionally characteristic of the cracks. Furthermore, the influences of localized plastic deformation and stress states on the SCC process are studied. This novel phase‐field framework can capture (1) the influences of coupled electricity, mechanics to the SCC mechanisms; (2) the contribution of plastic strain energy as the driving force for the phase‐field; (3) the potential and preferential crack initiation and propagation morphology within the complex stress and strain domain; and (4) the dependence of SCC rate and propagation direction on stress state and localized plastic deformation.

A review on AI-driven environmental-assisted stress corrosion cracking properties of conventional and advanced manufactured alloys

Stress corrosion cracking (SCC) poses a significant challenge to the integrity and longevity of both conventional and advanced manufactured alloys, impacting critical industries such as aerospace, marine, and nuclear energy. This review explores the use of artificial intelligence (AI) to analyse and predict SCC properties. Traditional alloys such as steel, aluminium, and titanium, as well as advanced materials such as additive-manufactured and high-entropy alloys, exhibit unique SCC behaviours influenced by corrosive environments, mechanical stress, and temperature variations. AI techniques, including machine learning models, offer transformative approaches to understanding and mitigating SCC. Leveraging extensive datasets from experiments and field studies, AI can identify patterns and correlations that traditional methods might miss. Predictive modelling through supervised learning forecasts SCC initiation and propagation, aiding in material design and maintenance. Unsupervised and reinforcement learning enhances alloy composition and processing parameter optimisation for better SCC resistance. In conventional alloys, AI identifies specific SCC conditions, leading to improved protective measures. For advanced alloys, AI-driven insights tailor additive manufacturing processes and design high-entropy alloys with superior corrosion resistance. This review includes case studies demonstrating AI's effectiveness in predicting SCC across various alloy–environment combinations, highlighting successes and challenges. Despite hurdles such as data quality and integration, AI holds immense potential to revolutionise SCC research, enhancing understanding of SCC mechanisms and fostering innovations in alloy design and preventative maintenance.

Intergranular corrosion and stress corrosion cracking properties evaluation and mechanism study of multi-microalloyed 2519 Al alloy

In this paper, the microstructure of the alloy has been modulated by the multivariate microalloying technique, aiming to reveal the intrinsic relationship and mechanism of intergranular corrosion and stress corrosion cracking. The addition of V to 2519 alloy changed the distribution characteristics of grain boundary precipitates and the dislocation density was reduced by 22.5 %, and the intergranular and stress corrosion cracking properties of the alloy were improved by 14.1 % and 40.7 %, respectively. Interestingly, grain deflection with <XXY>/48°-58° axial angle relationship was found during stress corrosion crack propagation and the alloy had the best stress corrosion resistance.

A Study on the Propagation of Chloride-Induced Stress Corrosion Cracking for Austenitic Stainless Steel at Corrosion Environment

Austenitic stainless steels have been widely used in the petrochemical industry, nuclear power plants and the ship industry due to their high toughness and corrosion resistance. However, these materials are susceptible to environmentally-assisted degradation, such as chloride-induced stress corrosion cracking (CISCC). In this respect, this study investigated CISCC crack propagation rate for austenitic stainless steels, such as type 304L and type 316L, in the corrosion environment. Considering the environment of the spent nuclear fuel canister used in the dry storage system, the test chamber is always maintained at 3.5% NaCl and related humidity (RH) 95% at 60℃. For initiation of CISCC, a test procedure, which has nine pre-cracking procedures for a CT specimen, is suggested. In a test procedure, crack transitioning, which induces the environmental corrosion crack, is observed after mechanical precracking. To determine the CISCC crack length corresponding to each test step, the direct current potential drop (DCPD) method is measured in real-time. In addition, the CISCC crack observed after final fracture is measured using optical microscopy in order to improve the accuracy of the measured crack length. In the test results, CISCC crack resistance of type 316L is better than that of type 304L. Finally, the test results show that the CISCC crack propagation rate is 2.784E-11 m/s for type 304L and is 9.93E-11 m/s for type 316L.

Quantification of SCC mechanisms in austenitic alloys under PWR primary water conditions

Abstract In order to achieve a full mechanistic understanding of stress corrosion cracking (SCC), the key operating mechanisms need to be identified but also quantified. In this study, we summarize and rationalize key findings from the last 15 years of high-resolution characterization of SCC in our group. A comprehensive characterization of a set of austenitic alloys with different Ni content and constant Cr level, tested under simulated pressurized water reactor (PWR) primary water conditions at various temperatures, has revealed evidence for at least two operating mechanisms: one diffusion-related and the other deformation-related. For their relevance to the nuclear industry, two additional alloys with increased Cr content were also studied (A800 and A690). Key precursors for SCC initiation and propagation are identified and their effect on alloy degradation discussed. A list of key materials’ properties that ensure low SCC susceptibility is proposed.

A comparative study on the passive film and SCC behavior of Ti-6Al-3Nb-2Zr-1Mo alloy at various test temperatures in simulated seawater

In this work, the electrochemical and stress corrosion cracking (SCC) behavior of Ti-6Al-3Nb-2Zr-1Mo alloy in simulated seawater at various solution temperatures were systematically studied. Results show rising test temperature increases the point defect density in passive film and deteriorates the stability. Therefore, SCC is promoted by localized anodic dissolution (AD). At 25 °C, SCC initiates in αp phase, and β phase hinders SCC propagation on account of the lower electrochemical activity induced by element segregation. While at 4 °C, the SCC propagation rate is higher than that at 25 °C, as the SCC propagation resistance of β phases decreases.

Effect of laser shock peening on stress corrosion cracking of TC4/2A14 dissimilar metal friction stir welding joints

Stress corrosion cracking (SCC) of welded joints is a significant issue that affects the widespread application of multimetal welded structures in aerospace, transportation, and other fields. This paper investigates the effect of laser shock peening (LSP) on the SCC of TC4/2A14 friction stir welded (FSW) joints with dissimilar metals. The microstructural evolution, mechanical properties, and corrosion behavior with and without LSP treatment were investigated using optical microscopy, transmission electron microscopy, X-ray analysis, electrochemical testing, and slow strain rate tensile testing (SSRT). The results showed that the LSP significantly refined the grains and induced work-hardening on the near-surface of the material. After LSP, the compressive residual stresses on the surface of the titanium and aluminium sides were −817.6 MPa and −153.6 MPa for the joint, respectively. Corrosion resistance was also improved, with the self-corrosion current density on the Al side of the joints reduced by 77% and the SCC susceptibility index (Issrt) reduced from 0.140 to 0.121. The enhanced SCC resistance of the LSP-treated TC4/2A14 dissimilar metal FSW joints is primarily due to grain refinement, work-hardening effect, and high-level compressive residual stress. These factors not only enhance the material strength and improve the pitting resistance of the joints but also prevent the initiation and propagation of SCC.

Stress corrosion crack propagation behaviour of MAO ceramic coating on Mg alloy

This study investigates the impact of static tensile loads on magnesium (Mg) alloys with and without ceramic coatings in simulated body fluids (SBF) using a combination of numerical simulation and experimental methods. The surface of an AZ31B Mg alloy was treated with a ceramic coating via micro-arc oxidation (MAO). Subsequently, bare Mg-alloy and MAO ceramic-coated specimens were subjected to static tensile stress testing using a tensiometer. After immersion for 12 h in SBF, the surface morphology and electrochemical corrosion of the stressed specimens were analysed. Notably, under the same tensile stress, the Mg alloy in the SBF exhibited more severe corrosion damage than the ceramic-coated specimen. Furthermore, there was a direct correlation between the corrosion rate of the ceramic coating and the magnitude of the applied tensile stress. Overall, the MAO ceramic coating exhibited superior corrosion resistance compared to the bare Mg alloy, even after undergoing static tensile stresses. The study demonstrates that MAO ceramic coatings can enhance the corrosion resistance of biodegradable Mg implants by protecting them from the combined effects of bodily stresses and fluids.

Assessing the release, transport, and retention of radioactive aerosols from hypothetical breaches in spent fuel storage canisters

Interim dry storage of spent nuclear fuel involves storing the fuel in welded stainless-steel canisters. Under certain conditions, the canisters could be subjected to environments that may promote stress corrosion cracking leading to a risk of breach and release of aerosol-sized particulate from the interior of the canister to the external environment through the crack. Research is currently under way by several laboratories to better understand the formation and propagation of stress corrosion cracks, however little work has been done to quantitatively assess the potential aerosol release. The purpose of the present work is to introduce a reliable generic numerical model for prediction of aerosol transport, deposition, and plugging in leak paths similar to stress corrosion cracks, while accounting for potential plugging from particle deposition. The model is dynamic (changing leak path geometry due to plugging) and it relies on the numerical solution of the aerosol transport equation in one dimension using finite differences. The model’s capabilities were also incorporated into a Graphical User Interface (GUI) that was developed to enhance user accessibility. Model validation efforts presented in this paper compare the model’s predictions with recent experimental data from Sandia National Laboratories (SNL) and results available in literature. We expect this model to improve the accuracy of consequence assessments and reduce the uncertainty of radiological consequence estimations in the remote event of a through-wall breach in dry cask storage systems.

Pioneering research on the role of strain burst in the early-stage stress corrosion crack propagation

This work pioneered the study on the effect of cyclic-loading-induced strain burst on Stage-1b stress corrosion crack (SCC) growth under alternating static and cyclic loading. Results show that Stage-1b growth occurred by microcrack initiation and its linking to the main crack's tip. Increasing static hold duration caused crack growth rate per cycle to increase after an incubation period. This was because the occurrence of strain burst induced a high strain rate, leading to film rupture, and thus microcrack initiation. The effects of different stress levels and durations of static hold, and their interactions with cyclic loading, on crack growth were systematically studied.

Stress Corrosion Cracking of High-Strength Ni-Base Alloys in Pressurized Water Reactor Primary Water Containing KOH vs. LiOH

The stress corrosion cracking (SCC) behavior of high-strength Ni-base Alloys X-750 and 718 has been investigated to assess the effect of replacing LiOH with KOH as the pH moderator in pressurized water reactor (PWR) primary circuit coolant. The SCC initiation behavior of X-750 was evaluated by multitensile specimen constant load test in either LiOH- or KOH-containing PWR primary water. The SCC growth behavior of X-750 and Alloy 718 was evaluated on compact tension specimens with on-the-fly changes between LiOH- and KOH-containing water in three different PWR primary water chemistries. Direct current potential drop technique was used for in situ monitoring of crack initiation time and crack extension in SCC initiation and propagation tests, respectively. The results suggest no significant effect of KOH vs. LiOH on the SCC initiation or propagation of the tested materials.

Stress Measurement of Stainless Steel Piping Welds by Complementary Use of High-Energy Synchrotron X-rays and Neutrons

Probabilistic fracture mechanics (PFM) is increasingly recognized as a viable approach for evaluating the structural integrity of nuclear components, such as piping, primarily affected by stress corrosion cracking (SCC). PFM analysis requires several input parameters, among which welding residual stress is critically important due to its significant influence on SCC initiation and propagation. Recently, a novel technique involving a double-exposure method (DEM) utilizing synchrotron X-rays was introduced as an effective means for measuring welding residual stress with high spatial resolution. In this paper, we applied DEM to assess the residual stress of a plate specimen, which was extracted from a welded pipe through electrical discharge machining. Consequently, detailed stress maps under a plane stress state were generated. Additionally, the residual stress distributions in the welded pipe under a triaxial stress state were evaluated using neutron diffraction. Based on these findings, we proposed a methodology to acquire detailed stress maps of welded pipes by combining high-energy synchrotron X-rays and neutron diffraction.

Electrochemical potential dependence of SCC initiation in X60 pipeline steel in near-neutral pH environment

Stress corrosion crack (SCC) in pipelines directly affects the long-term safety service and has a major impact on the continuity of oil and gas delivery. The near-neutral pH SCC propagation process has been widely reported in the past decades, while the crack initiation mechanism is rarely studied in-depth. Here, the crack initiation behavior of ×60 pipeline steel under different electrochemical potential levels was investigated by interrupted slow strain rate tensile testing (SSRT) and microstructural characterization. The experimental results show that the SCC initiation is dominated by hydrogen-facilitated anodic dissolution (AD) under the open circuit potential (OCP) environment, while it is by the hydrogen embrittlement (HE) under −1.1 and −1.2 VSCE cathodic potentials. All the SCC cracks in ×60 pipeline steel show transgranular features, pathing through the grains in different crystallographic orientations, which showed dependence on the electrochemical potential of the steel: initiation via slip-enhanced dissolution of {110}//ND or {112}//ND texture under OCP environment, but mostly by quasi-cleavage cracking of {100}//ND texture under −1.1 and −1.2 VSCE cathodic potentials.

Insights into the stress corrosion cracking propagation behavior of Alloy 690 and 316 L stainless steel in KOH versus LiOH oxygenated water

The stress corrosion cracking (SCC) propagation behavior of 20% cold worked 316 L stainless steel (SS) and Alloy 690 was investigated in high-temperature oxygenated water. No discernable effect was observed at the same pH level for LiOH or KOH. Increasing pH could dramatically enhance the crack growth rates (CGRs) due to the dissolution of Cr-rich oxide film and the weakening of passivity in high pH regimes. The similarities in SCC behavior and cracking characteristics indicate that the cracking mechanism of both austenite alloys occurs by a slip-dissolution model.

Effect of Thermo-Mechanical Processing on Initiation and Propagation of Stress Corrosion Cracking in 304L Austenitic Stainless Steel

Despite the high corrosion resistance of austenitic stainless steels (SSs), a significant reduction of stress corrosion cracking (SCC) resistance has been reported in cases of high residual stress and metastable microstructural features. In this study, the effect of thermo-mechanical processing (TMP) on the initiation and propagation of SCC in 304L SS was studied. To better understand the SCC mechanisms, three TMPs conditions—welded, solution annealed at 1050 °C for tens of seconds, and straightened—were used. The research focused on analyzing the initial microstructure, residual stress, and hardness along the depth direction to assess SCC resistance and establish correlations with the observed SCC modes. Experimental results demonstrated that transgranular SCC was observed in regions exhibiting elevated residual stress induced by welding and straightening processes. Furthermore, the presence of strain-induced martensite transformation and slip bands formed during plastic deformation were identified as additional factors contributing to the susceptibility of SCC. The study findings highlighted that the magnitude and distribution of residual stresses, in conjunction with microstructural evolution, could be varied depending on the specific TMP condition, leading to different SCC susceptibilities, cracking modes, and directions.

Insights into the effects of δ-ferrite on crack tip stress/strain and stress corrosion cracking propagation behavior of austenite weld metal: A numerical and experimental study

The effects of δ-ferrite on stress corrosion cracking behaviors of austenite weld metal were analyzed by a ferrite-crack model. The results show that the δ-ferrite might inhibit the crack propagation initially once the crack tip meets it by reducing the local plastic strains. Thereafter, the crack might still propagate either along the δ-ferrite boundary (intergranular, IG) or across the δ-ferrite (transgranular, TG). The IG cracking will accumulate much more plastic strains at the crack tip and tends to promote crack growth. The TG cracking might be enhanced by the oxidation-induced embrittlement of the δ-ferrite.

Innovative prevention of stress corrosion crack propagation in nuclear power pipe welds

Abstract Failure caused by stress corrosion cracking (SCC) is inevitable during the long-term service of nuclear power pipe welds. This is mainly due to the propagation of microcracks in the deposited metal, which seriously affects the operation safety of nuclear power pressure pipes. Overlay welding is practical for pressure pipe repair welding, which can introduce compressive residual stress inside the weld seam. In this work, a diagonal T-pipe joint was fabricated using tungsten inert gas arc welding with ERRS-3 wire, and an overlay weld was also fabricated using tungsten inert gas arc welding with ERRS-3 wire under circumstances of water in the pipe and no water in the pipe. And then the contour method and finite element method were employed to measure and calculate the residual stress distribution in the diagonal T-pipe joint. Both results showed that overlay welding can introduce compressive residual stresses into the pipe joint. The compressive residual stress zone area inside the weld seam with water in the pipe is larger than that without water in the pipe, and the compressive residual stress zone area varies at different positions of the weld seam. This work is expected to promote the application of overlay weld technology in the diagonal T-shaped pipe joint repair and prevent stress corrosion crack propagation of nuclear power pipe welds.

Characterisation of stress corrosion durability and time-dependent performance of cable bolts in underground mine environments

Premature failures of cable bolt caused by stress corrosion cracking (SCC) has been more and more often observed with the increasing depth of underground mines. Investigating and predicting this failure are critical in maintaining and accessing the integrity of the reinforcement system. In this study, with application of the designed SCC-AE testing system, the SCC failure processes of cold-drawn cable bolts used in underground reinforcement system was investigated using the acoustic emission (AE) techniques in simulated underground conditions. Damage evolution of the specimens was monitored with AE in real-time. The scanning electron microscopy was adopted to examine the fractographic features of the failed specimen. Through the integrated analysis of specimens’ elongation, the evolution of acoustic activities and fractographic features, three different stages during SCC failure processes were determined including cracks initiation due to the local corrosion, cracks propagation characterised as tear ridges appearance and fast fracture failure evidenced by the shear lips. The parameters of elongations, AE signals in each failure stage were investigated and the SCC propagation rates were determined. As a result, this study confirms the AE technique in combination with the designed testing system can give important insights into the SCC failure as well as the possibilities of real-time SCC monitoring in underground reinforcement systems.