Stress Corrosion Cracking Mechanism Research Articles

Anisotropic stress corrosion cracking susceptibility of Mg-8Gd-3Y-0.5Zr alloy

This study investigates the stress corrosion cracking (SCC) behavior of a Mg-8Gd-3Y-0.5Zr alloy in a 3.5 wt.% NaCl solution using slow strain rate tensile (SSRT) testing. The results reveal that SCC susceptibility increases as the strain rate decreases, with hydrogen embrittlement (HE) becoming more dominant at lower strain rates, leading to brittle fracture. Anodic dissolution (AD) plays a more significant role at higher strain rates, resulting in mixed fracture modes. Additionally, the mechanical properties and SCC resistance are strongly influenced by the sample orientation. TD-oriented samples show higher SCC susceptibility than RD-oriented ones due to the alignment of Gd- and Y-rich precipitates and grain boundaries, which act as initiation sites for SCC. These precipitates form micro-galvanic couples with the Mg matrix, accelerating localized corrosion and HE. The findings provide insights into the SCC mechanisms of VW83 alloy and highlight the importance of optimizing microstructure and processing conditions to improve its corrosion resistance.

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.

Stress corrosion cracking behaviors of carbon steel in liquid ammonia

As a carbon-free hydrogen-rich energy carrier, ammonia has gained increasing attention and application in the context of carbon peaking and carbon neutrality. This study evaluated the stress corrosion cracking (SCC) sensitivity of four target materials, A516-70, 16MnDR, 15MnNiDR, and Q370DR, in a liquid ammonia environment at 25 °C and 1.03 MPa by slow stress rate tests to determine their SCC sensitivity index. The microstructure, grain size, misorientation, hardness, strength, and micro-fracture morphology of these materials were compared to analyze the SCC mechanism. The results showed that 15MnNiDR exhibited significant SCC sensitivity while both 16MnDR and A516-70 demonstrated certain levels of SCC sensitivity in liquid ammonia. However, Q370DR showed no SCC sensitivity under these conditions. The misorientations observed align with the strains experienced by each respective carbon steel in liquid ammonia. An unstable passivation film formed on the surface of 15MnNiDR steel when exposed to liquid ammonia whereas Q370DR developed a stable oxide film which contributed to its weak SCC sensitivity.

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.

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.

Review on Environmentally Assisted Static and Fatigue Cracking of Al-Mg-Si-(Cu) Alloys

This paper reviews the relevant literature and covers the main aspects of the environmentally assisted cracking of Al-Mg-Si-(Cu) alloys. Apart from a brief overview of the major microstructural and mechanical properties, it presents research results on the corrosion sensitivity and stress corrosion susceptibility of Al-Mg-Si alloys. Possible mechanisms of stress corrosion cracking and corrosion fatigue in aluminum alloys, such as anodic dissolution and/or interaction with hydrogen, are considered. A number of factors, including atmospheric or solution conditions, applied stress, and material properties, can affect these mechanisms, leading to environmentally assisted cracking. Specific attention is given to Al-Mg-Si alloys with copper, which may increase the sensitivity to intergranular corrosion. The susceptibility to both intergranular corrosion and stress corrosion cracking of Cu-containing Al-Mg-Si alloys is mostly associated with a very thin layer (segregation) of Cu on the grain boundaries. However, the effect of Cu on the corrosion fatigue and fatigue crack growth rate of Al-Mg-Si alloys has received limited attention in the literature. At the current state of the research, it has not yet been holistically assessed, although a few studies have shown that a certain content of copper can improve the resistance of aluminum alloys to the environment with regard to corrosion fatigue. Furthermore, considerations of the synergistic actions of various factors remain essential for further studying environmentally assisted cracking phenomena in aluminum alloys.

New insights into stress corrosion cracking mechanism of Alloy 600 in boiling water reactor (BWR) environment

Several mechanisms have been proposed to explain the intergranular stress corrosion cracking (IGSCC) of Alloy 600 in BWR, but slip-dissolution at grain boundaries remains the most recognized cause. However, it is still uncertain whether the above degradation is accompanied by selective internal oxidation (SIO) as a precursor. Following new insights into the creviced bent beam (CBB) test, relevant evidence was discovered. Additionally, the results of First Principle Calculation indicate interstitial O actively competes for chromium in IG carbides to form chromium oxides during the SIO process, instead of passively waiting for the oxidation/decomposition of carbides to provide a chromium source.

Stress corrosion cracking behavior and mechanism of 2205 duplex stainless steel under applied polarization potentials

In this work, a non-steady electrochemical model for assessing stress corrosion cracking (SCC) of 2205 duplex stainless steel (DSS) under applied polarization potentials was proposed, and the SCC mechanism was revealed. With the negative shift of potentials, hydrogen enhances SCC susceptibility by deteriorating passive film, inhibiting repassivation and causing serious damage. In particular, at −850 mV (vs. SCE), the synergetic effect of anodic dissolution (AD) and hydrogen embrittlement (HE) causes severe pitting and SCC. The negative shift of applied potentials changes the preferential pit/SCC initiation site due to high hydrogen concentration in austenite.

Study of stress corrosion cracking susceptibility of irradiated ferrite-martensitic stainless steel 07Kh12NMFB in supercritical water. Part 2. Development of corrosion crack identification technique and analysis of autoclave test results

The studies of stress corrosion cracking have been carried out for the stainless ferritic-martensitic steel with chromium content of 12% irradiated to a damage neutron dose of ~12 dpa. This steel was chosen as a candidate material for the internals of supercritical water-cooled reactors (SWCR).The first part of the paper was devoted to autoclave testing of specially designed disk specimens under constant load in a supercritical water environment (at 450°C and 250 atm pressure). In this part of the article the developed technique for corrosion cracks identification is presented and analysis of autoclave tests results is performed.As a result of the experiments performed, the threshold stress values below which stress corrosion cracking initiation doesn’t occur. The values of threshold stresses are determined for the studied steel irradiated at temperatures of 390 and 550°C. Possible mechanisms of stress corrosion cracking of the studied steel are analyzed and directions for further research are proposed.

In vitro evaluation of stress corrosion cracking susceptibility of PEO-coated rare-earth magnesium alloy WE43

Controlling material degradation in complex mechanobiological environments is the current challenge in advancing biodegradable magnesium implants for orthopaedic applications. Understanding stress corrosion cracking (SCC) mechanisms of magnesium alloy-coating systems in physiological fluids facilitates the design of magnesium implants with excellent biomedical performance. In this study, we investigated the SCC behaviour of a medical grade PEO-coated magnesium alloy WE43 under different loading conditions. Constant loadings tests (CLT) and slow strain rate tests (SSRT) were conducted to evaluate the SCC susceptibility of this alloy-coating system under in vitro conditions. Fracture surfaces of the non-coated and PEO-coated specimens were characterised by scanning electron microscopy to reveal the SCC mechanisms under different loading configurations. The experimental results showed that the alloy-coating system exhibits a high SCC resistance in SSRT conditions. However, high stress levels and plastic deformations lead to a significant acceleration of the SCC process. Moreover, the fracture surface analysis demonstrated that the brittle nature of the PEO coating deteriorates the mechanical integrity of the alloy under critical mechanical loadings, which results in an increased susceptibility towards stress corrosion cracking of the coated WE43.

Data Mining Applied to the Electrochemical Noise Technique in the Time/Frequency Domain for Stress Corrosion Cracking Recognition

In this paper, time/frequency domain data processing was proposed to analyse the EN signal recorded during stress corrosion cracking on precipitation-hardening martensitic stainless steel in a chloride environment. Continuous Wavelet Transform, albeit with some limitations, showed a suitable support in the discriminatory capacity among transient signals related to the different stress corrosion cracking mechanisms. In particular, the aim is to propose the analysis of electrochemical noise signals under stress corrosion cracking conditions in the time–frequency domain by using the Hilbert–Huang approach. The Hilbert–Huang Transform (performed by the Empirical Mode Decomposition approach) was finally proposed to carry out an identification of the corrosion mechanisms in comparison to conventional data processing methods. By using this approach, a detailed simultaneous decomposition of the original electrochemical noise data in the time and frequency domain was carried out. The method gave useful information about transitions among different corrosion mechanisms, allowing us to (i) identify a specific characteristic response for each corrosion damaging phenomenon induced by stress corrosion cracking, (ii) time each corrosion of the damaging phenomenon, and (iii) provide a topological description of the advancing SCC damaging stages. This characteristic evidences that the Hilbert–Huang Transform is a very powerful technique to potentially recognize and distinguish the different corrosion mechanisms occurring during stress corrosion cracking.

Influence of AC/DC on stress corrosion cracking of Ti-6Al-3Nb-2Zr-1Mo alloy in simulated marine solution

The study investigated the influence of alternating current (AC) and direct current (DC) on stress corrosion cracking (SCC) behavior of Ti-6Al-3Nb-2Zr-1Mo (Ti80) alloy in simulated marine solution with different pH levels. Electrochemical measurements, slow strain rate tensile (SSRT) tests and fracture morphology analysis were used to evaluate SCC behavior. Under conditions of pH = 2 or 1, AC enhances SCC susceptibility by disrupting the passive film, primarily attributed to anodic dissolution and hydrogen embrittlement. When both AC and DC coexist, the excessively negative potential intensifies the hydrogen evolution reaction, leading to hydrogen embrittlement dominating the SCC mechanism of Ti80.

Understanding the non-steady electrochemical mechanism on SCC of 304 SS under applied polarization potentials

In this work, the non-steady electrochemical model on stress corrosion cracking (SCC) was established, which was verified by SCC of 304 SS with various microstructures. SCC mechanism depends on applied potentials including anodic dissolution (AD), hydrogen embrittlement (HE) and AD+HE, and the potential range for each mechanism was determined with the critical potentials on slow/fast scan potentiodynamic curves. The quantitative relationship of SCC susceptibility and applied potentials is acquired with the model, which is effective for assessing SCC. It was verified by 304 SS with various microstructures, which presents similar non-steady electrochemical characteristics and SCC susceptibility.

Effect of low dose irradiation of heavy ion on electrochemical corrosion and IASCC behavior of austenitic steel

The impacts of low dose irradiation on the behavior of electrochemical corrosion and irradiation assisted stress corrosion cracking for 321 stainless steel were studied using Fe2+ ion irradiation to simulate neutron radiation damage in primary circuit environment of pressurized water reactor. Low dose irradiation can improve the pitting resistance and reduce the cracking tendency of the alloy in B-Li solution to a certain extent, which was related to the δ phase content on the near-surface of the sample: The higher δ phase content on the near-surface of the 2 dpa irradiated sample was observed by grazing incident X-ray diffraction. In addition, the pits was significantly increased near micro-cracks for the unirradiated sample, indicating that the existence of pits induced the initiation of cracks. The research results provided an important reference for the failure mechanism of irradiation assisted stress corrosion cracking of core components.

Effect of alternating current on the electrochemical behavior and stress corrosion cracking of TA2 in simulated marine environment

This study investigated the effect of alternating current (AC) on the electrochemical and stress corrosion cracking (SCC) behavior and mechanism of TA2 in a simulated marine solution. The increase in the open circuit potential and charge transfer resistance indicated that the passivation film remained undamaged by varying AC densities, indicating a low risk of SCC. However, under the synergistic effect of AC and direct current (DC), the potential significantly shifted negatively, leading to hydrogen evolution reactions and the formation of a hydride layer. This hydride-induced hydrogen embrittlement posed a potential risk to the integrity of TA2.

Stress corrosion cracking behavior on carbon steel under the synergistic effect of chloride and bicarbonate ions in alternating wet-dry environment

The stress corrosion cracking mechanism of X80 carbon steel under the combined actions of chloride and bicarbonate ions in alternating wet-dry environment was investigated by performing slow strain rate tensile test and in-situ electrochemical detection during the SCC process under constant load. The results showed that the oxidation and reduction reaction cycle of iron oxide during wet-dry cycle would accelerate the corrosion process. The pitting under the corrosion product layer at high concentrations of chloride and bicarbonate was the origin of SCC under the action of stress concentration, which made steel display high SCC susceptibility.

Improving Corrosion and Stress Corrosion Cracking Performance of Machined Biodegradable Alloy ZX20 by HF-Treatment

The treatment with hydrofluoric acid (HF-treatment) was suggested to be an effective way of improving the corrosion resistance of Mg alloys, including Mg-Zn-Ca (ZX) ones used for biodegradable implants. However, the effect of the HF-treatment on the stress corrosion cracking (SCC) susceptibility of ZX alloys has not been reported yet, although this phenomenon can induce premature brittle failures of the metallic medical devices, and thus, it is critical for their in-service structural integrity. In the present study, the effect of the HF-treatment on the microstructure, cytotoxicity, corrosion rate, mechanical properties, and fracture and side surface characteristics of the as-cast ZX20 alloy were investigated with the use of scanning electron microscopy, immersion, and slow-strain rate tensile testing in Hanks’ solution and indirect cell viability tests. It is found that the HF-treatment exerts no cytotoxic effect and results in a significant reduction in corrosion rate (up to 6 times of magnitude) and SCC susceptibility indexes (up to 1.5 times of magnitude). The observed improvement of corrosion and SCC performance of the alloy by the HF-treatment is found to be attributed to three effects, including (i) formation of the protective surface film of MgF2, (ii) removal of surficial contaminations originating from sample preparation procedures, and (iii) dissolution of surficial secondary phase particles. The mechanism of corrosion and SCC in the specimens before and after the HF-treatment are discussed.

The synergistic effect of parallel magnetic field and sulfate-reducing bacteria on stress corrosion cracking of buried X80 pipeline steel

In this work, the synergistic effect of parallel magnetic field and sulfate-reducing bacteria (SRB) on stress corrosion cracking (SCC) of X80 pipeline steel in buried soil environments was investigated for the first time by electrochemical experiments, slow strain rate tensile tests (SSRT) and surface characterization. The results showed that the parallel magnetic field suppressed electrochemical corrosion in a sterile environment; the SCC susceptibility decreased with increasing magnetic field strength (0–100 mT). The magnetic field and SRB synergistically promoted the formation of a dense film layer on the surface of the specimen in the inoculated SRB environment. The dense film layer suppresses the local corrosion of the metal and therefore the SCC susceptibility is reduced. The suppression effect no longer increased significantly when the magnetic field strength reached 75 mT. The synergy between the parallel magnetic field and the SRB was responsible for the reduced susceptibility of the SCC. This work contributed to a more in-depth study of the mechanisms of pipeline SCC and the development of pipeline SCC prevention technologies.

Stress corrosion cracking failure of X80 carbon steel U-bend caused by Desulfovibrio vulgaris biocorrosion

Sulfate reducing bacteria (SRB) are widely present in oil and gas industry, causing pitting corrosion on pipeline steel. Stress corrosion cracking (SCC) often occurs in the presence of mechanical stress before pitting perforation failure, leading to economic losses and even catastrophic accidents. In this study, stress distribution simulation using the finite element method (FEM), corrosion analysis techniques and electrochemical corrosion measurements were employed to investigate the SCC mechanism of X80 pipeline steel caused by Desulfovibrio vulgaris, which is a common SRB strain used in microbiologically influenced corrosion (MIC) studies. It was found that D. vulgaris MIC caused sharp microcracks on an X80 U-bend coupon after only 2 weeks of immersion at 37 °C in the deoxygenated ATCC 1249 culture medium inoculated with D. vulgaris. The X80 U-bend coupon's weight loss-based uniform corrosion rate for the 12 cm2 surface was 60% of that for the unstressed flat square coupon (2.3 mg cm−2 vs. 3.8 mg cm−2). This was likely because the square coupon had wide MIC pits, providing a larger effective surface area for more sessile cells (4.2×108 cells cm−2 on square coupon vs. 2.4×108 cells cm−2 on U-bend coupon) to attach and harvest more electrons. An SCC failure occurred on an X80 U-bend pre-cracked at the outer bottom after a 6-week immersion in the D. vulgaris broth. Apart from MIC damage, this could also be because D. vulgaris metabolism increased the availability hydrogen atoms on the steel surface, and promoted the diffusion of hydrogen atoms into the metal lattice, thus increasing the brittleness of the steel.