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To address the issue that 2205 duplex stainless steel (DSS) of reboiler tube bundle is prone to stress corrosion cracking (SCC) under high temperature, high chloride, and dissolved oxygen (DO), the SCC mechanism of 2205 DSS was investigated in this paper in an oxygen–chloride synergistic corrosion environment. To characterize the fracture morphology of SCC under different oxygen–chloride conditions, the slow strain rate tensile (SSRT) test was used. SSRT tests were performed on 2205 DSS in high temperature (100°C–200°C), high salt (0–150,000 mg/L), and different DO (0–20 mg/L) corrosive environments. As the DO (0–20 mg/L), chloride ion concentration (0–150,000 mg/L), and temperature (100°C–200°C) increased, so did the elongation, internal product work, and stress corrosion cracking tendency of 2205 DSS. A stress corrosion sensitivity index F(A) calculation model was established, incorporating the interaction of temperature, chloride ions, and dissolved oxygen. The rupture of the passivation film and the superposition of anodic dissolution are the failure mechanisms of 2205 DSS. Transgranular stress corrosion cracking is caused by the rupture of the passivation film, which accelerates the failure process and eventually causes 2205 DSS to rupture. [ABSTRACT FROM AUTHOR]

Stainless-steel is extensively utilized in the key structural components of the main equipment in the nuclear island of pressurized water reactor nuclear power plants. The operational experience of nuclear power plants demonstrates that stress corrosion is one of the significant factors influencing the long-term safe operation of stainless steel in the high-temperature water of pressurized water reactor nuclear power plants. This study is based on the stress corrosion crack growth rate data of 316SS and 304SS stainless steel in the simulated primary water environment of pressurized water reactor nuclear power plants. Data mining and modeling were conducted using multiple machine learning algorithms, including Random Forest (RF), eXtreme Gradient Boosting (XGBoost), Support Vector Regression (SVR), and Gaussian Process Regression (GPR), and the Sharpley Additive explanation (SHAP) method was employed to analyze the interpretability of the model. The results indicate that the stress corrosion crack growth rate prediction model based on XGBoost outperforms other models in all assessment indicators. Compared with empirical equations, XGBoost exhibits high flexibility and excellent data-driven learning capabilities. In the test set, 90% of the prediction errors are within the range of experimental values, with the maximum error multiple being 2.5, which significantly improves the prediction accuracy. Moreover, the distribution of SHAP values is consistent with the theoretical study of the stress corrosion behavior of stainless-steel, effectively reflecting the impact of cold working, temperature, and stress intensity factor on the stress corrosion crack growth rate, thereby proving the reliability of the model's prediction results. The achievements of this study hold significant reference value and application prospects for the prediction of the stress corrosion behavior of stainless-steel in a high-temperature and high-pressure water environment of pressurized water reactor nuclear power plants. [ABSTRACT FROM AUTHOR]

This review aims to study the process plant damage mechanisms published by previous research, such as general corrosion, localised corrosion, and stress corrosion cracking. This review was conducted by analysing the current application of the common inspection method and technique and focusing on the phased array ultrasonic testing application. In order to further the current study, the review seeks direction on evaluating phased array corrosion mapping techniques to detect corrosion and metal loss during plant operation and minimise the plant’s need for maintenance. This systematic literature review provides a better understanding of the current damage mechanisms and shows the possibility of an extended future study. [ABSTRACT FROM AUTHOR]

Fractography of stress corrosion cracking (SCC) of 20% cold worked Type 304 H stainless steel containing δ-ferrite was studied using a compact tension (CT) specimen in oxidizing primary water with a scanning electron microscope (SEM) and electron back scattered diffraction (EBSD). The stress corrosion crack propagated mostly in transgranular stress corrosion cracking (TGSCC) mode and sometimes in intergranular stress corrosion cracking (IGSCC) mode. TGSCC paths were along the {111} plane with both high resolved shear stress and high resolved tensile stress. IGSCC preferentially propagated along the grain boundary perpendicular to the loading axis. The findings in this work suggest that TGSCC proceeds through formation of a weakening zone at the head of the crack tip by interaction of slip and corrosion and then cracking of the weakened zone by tensile stress.

ABSTRACTIn this study, Al-Zn-Mg-Cu alloy components were prepared using wire arc additive manufacturing (WAAM). Through multi-scale characterisation technology, performance testing and slow strain rate tensile (SSRT) testing, the microstructure, mechanical properties and stress corrosion cracking (SCC) susceptibility of WAAM Al-Zn-Mg-Cu components were studied, revealing the generation mechanism of inhomogeneity and anisotropy. The results show that with the increase of WAAM thermal cycles, the matrix precipitates (MPs), grain boundary precipitates (GBPs) and precipitation-free zones (PFZ) evolve in different paths and increase to varying degrees, resulting in performance decrease and increase in stress corrosion susceptibility, so the inhomogeneity is mainly attributed to differences in precipitated phases. The Inter-layer inclined to the scanning direction and the Inner-layer inclined to the building direction led to anisotropy in tensile strength and SCC behaviour, so the anisotropy is mainly attributed to the grain orientation and fracture mode.

Measurements of residual stresses inherited by pipes during the pipe manufacturing process were carried out, and the relationship of SCC with these stresses in the pipe metal was studied. The obtained correlations demonstrate the possibility of optimizing the pipe manufacturing process to reduce their susceptibility to stress corrosion. [ABSTRACT FROM AUTHOR]

In this study, an external semi-elliptical crack was modeled in a 3D API 5 L X52 pipeline with stress corrosion cracking (SCC). To make the crack, the finite element method (FEM) was used to obtain the failure pressure (Pf) and its mechanical behavior. The longitudinal crack had a constant length (2c) and varied with depth (a). The properties of X52 steel subjected to SCC using the slow strain rate technique (SSRT) were considered. True stress-strain curves were obtained in air and in an NS4 solution with pHs of 3.5 and 9.5 at temperatures of 25 and 50 °C. According to the SCC index calculated from the mechanical properties of the SSRT, the X52 steel is susceptible to SCC at pH 3.5 and 50 °C. The mechanical properties of the tensile test using the stress-strain curves decreased as the pH and temperature changed, compared to those carried out at room temperature. This was due to the corrosion and hydrogen embrittlement produced by the solution on the X52 steel. The failure pressure is sensitive to the stress-strain curve; if the stress-strain curve decreases, the failure pressure also decreases. Corrosion defects, such as longitudinal cracks in X52 steel, which could be susceptible to SCC in an NS4 solution, decrease the failure pressure (Pf) and its capacity to withstand pressures of up to 75 % in pipe-grade steel that transports hydrocarbons.

Stainless-steel is extensively utilized in the key structural components of the main equipment in the nuclear island of pressurized water reactor nuclear power plants. The operational experience of nuclear power plants demonstrates that stress corrosion is one of the significant factors influencing the long-term safe operation of stainless steel in the high-temperature water of pressurized water reactor nuclear power plants. This study is based on the stress corrosion crack growth rate data of 316SS and 304SS stainless steel in the simulated primary water environment of pressurized water reactor nuclear power plants. Data mining and modeling were conducted using multiple machine learning algorithms, including Random Forest (RF), eXtreme Gradient Boosting (XGBoost), Support Vector Regression (SVR), and Gaussian Process Regression (GPR), and the Sharpley Additive explanation (SHAP) method was employed to analyze the interpretability of the model. The results indicate that the stress corrosion crack growth rate prediction model based on XGBoost outperforms other models in all assessment indicators. Compared with empirical equations, XGBoost exhibits high flexibility and excellent data-driven learning capabilities. In the test set, 90% of the prediction errors are within the range of experimental values, with the maximum error multiple being 2.5, which significantly improves the prediction accuracy. Moreover, the distribution of SHAP values is consistent with the theoretical study of the stress corrosion behavior of stainless-steel, effectively reflecting the impact of cold working, temperature, and stress intensity factor on the stress corrosion crack growth rate, thereby proving the reliability of the model’s prediction results. The achievements of this study hold significant reference value and application prospects for the prediction of the stress corrosion behavior of stainless-steel in a high-temperature and high-pressure water environment of pressurized water reactor nuclear power plants.

Herein, the stress corrosion cracking (SCC) susceptibility of duplex (UNS S32205) and austenitic (UNS S31653) stainless steel (SS) reinforcements was evaluated using integrity assessment criteria. Mechanical properties were analyzed and compared by different SCC susceptibility factors. The integrity assessment was conducted applying Cosenza, Creazza, and Ortega ductility criteria, following three different standards (ACI 318-19, ASTM A615, and FIB). A conventional carbon steel (UNS G10080) reinforcement was also evaluated for comparative purposes, whose high residual stress value (>280 MPa) promoted a high corrosion growth rate. Duplex UNS S32205 SS grade showed a significant decrease in elongation, leading to failure after ductility assessment at high chloride concentrations. Fractographic analysis of both SS grades, duplex and austenitic, revealed less than 40% brittle areas at 8 wt.% Cl−, while UNS G10080 had over 85% at 4 wt.% Cl−. [ABSTRACT FROM AUTHOR]

The main purpose of this study is to investigate the influence of retrogression and re-aging post weld heat treatment (RRA-PWHT) on potentiodynamic corrosion (PC) and stress corrosion cracking resistance (SCC) of stir zone (SZ) of AA7075-T651 alloy butt joints developed using friction stir welding (FSW). FSW was employed to overcome the problems in fusion welding of AA7075-T651 alloy such as solidification cracking, heat affected zone (HAZ) softening, grain coarsening, dissolution of strengthening precipitates and inferior mechanical performance. The SZ of joints were subjected to potentiodynamic corrosion test in 3.56 wt% NaCl solution. The circumferential notch tensile (CNT) specimens were subjected to SCC test at various conditions of axial stress level in 3.56 wt% NaCl solution. The microstructural features of butt joints SZ were characterized using optical (OM), scanning electron (SEM) and transmission electron microscope (TEM). The results disclosed that RRA-PWHT joints exhibited greater PC and SCC resistance compared to as-welded joints. The threshold stress level for the failure of CNT specimens of parent metal, as-welded joints and RRA-PWHT joints was 242 MPa, 175 MPa and 198 MPa, respectively. The threshold stress level of RRA-PWHT joints and as-welded joints is 81.81% and 72.31% of parent metal threshold stress level. It is correlated to increase in vol% and coarsening of grain boundary precipitates with enrichment of copper at the grain boundaries.

For studying the stress corrosion susceptibility of high manganese austenitic cryogenic steel HM400 in liquid ammonia medium, the slow strain rate test (SSRT) was used to investigate the stress corrosion susceptibility of high manganese austenitic cryogenic steel HM400 in four media: pure liquid ammonia (NH3), air+liquid ammonia (NH3+Air), 0.1 mg/L H2O+pure liquid ammonia (NH3+0.1 mg/L H2O) and air (Air) at room temperature. The fracture micro morphology, crack morphology, change of microstructure and mechanical properties of the samples before and after tests were characterized by scanning electron microscope (SEM), optical microscope (OM), X-ray diffractometer (XRD) and hardness tester. Results showed that strain strengthening occurred in high manganese austenitic cryogenic steel HM400 during tensile deformation. Moreover, HM400 steel possessed poor stress corrosion resistance in liquid ammonia medium, and hence it was not suitable as high parameterization and lightweight materials of liquid ammonia storage and transportation containers.

The stress corrosion cracking (SCC) behavior of X80 pipeline steel under Desulfovibrio desulfurican (D. desulfurican), alternating current (AC) and cathodic protection (CP) was studied by the constant load tests and slow strain rate tensile (SSRT) test. The results showed that both AC interference and relatively negative CP potential aggravated pitting corrosion and enhanced the SCC susceptibility under the constant load. In the saline soil environment containing D. desulfurican, the AC greatly contributed to the cracking tendency of X80 pipeline steel and resulted in the safe CP range that was too narrow for practical engineering application, thus requiring appropriate discharge methods.

The main purpose of this study is to investigate the influence of retrogression and re-aging post weld heat treatment (RRA-PWHT) on potentiodynamic corrosion (PC) and stress corrosion cracking resistance (SCC) of stir zone (SZ) of AA7075-T651 alloy butt joints developed using friction stir welding (FSW). FSW was employed to overcome the problems in fusion welding of AA7075-T651 alloy such as solidification cracking, heat affected zone (HAZ) softening, grain coarsening, dissolution of strengthening precipitates and inferior mechanical performance. The SZ of joints were subjected to potentiodynamic corrosion test in 3.56 wt% NaCl solution. The circumferential notch tensile (CNT) specimens were subjected to SCC test at various conditions of axial stress level in 3.56 wt% NaCl solution. The microstructural features of butt joints SZ were characterized using optical (OM), scanning electron (SEM) and transmission electron microscope (TEM). The results disclosed that RRA-PWHT joints exhibited greater PC and SCC resistance compared to as-welded joints. The threshold stress level for the failure of CNT specimens of parent metal, as-welded joints and RRA-PWHT joints was 242 MPa, 175 MPa and 198 MPa, respectively. The threshold stress level of RRA-PWHT joints and as-welded joints is 81.81% and 72.31% of parent metal threshold stress level. It is correlated to increase in vol% and coarsening of grain boundary precipitates with enrichment of copper at the grain boundaries. [ABSTRACT FROM AUTHOR]

The microrelief of thermally treated 40Kh steel after stress corrosion cracking (SCC) tests under the oxygen depolarization conditions has been analyzed. The microstructure formed after low and medium tempering contributes to the uniform formation of a microrelief during testing. Under the oxygen depolarization conditions, the device was tested with protective elements added to the design, which made it possible to preserve fractures during destruction, and the laser pointers helped to construct the dependence of deviation of capture with sample versus time. [ABSTRACT FROM AUTHOR]

Herein, the chloride-induced stress corrosion cracking (SCC) mechanisms of UNS S32205 duplex stainless steel (DSS) reinforcing bars in alkaline and carbonated solutions are studied. Electrochemical monitoring and mechanical properties were tested using linear polarization resistance and electrochemical impedance spectroscopy, coupled with the slow strain rate tensile test (SSRT) to evaluate the SCC behavior and unravel the pit-to-crack mechanisms. Pit initiation and crack morphology were identified by fractographic analysis, which revealed the transgranular (TG) SCC mechanism. HCO3− acidification enhanced the anodic dissolution kinetics, thus promoting a premature pit-to-crack transition, seen by the decrease in the maximum phase angle in the Bode plot at low frequencies (≈ 1 Hz) for the carbonated solution. The crack propagation rate for the carbonated solution increased by over 100% compared to the alkaline solution, coinciding with the lower phase angle from the Bode plots, as well as with the lower charge transfer resistance. Pit initiation was found at the TiN nonmetallic inclusion inside the ferrite phase cleavage facet, which developed TG-SCC. [ABSTRACT FROM AUTHOR]

• The fundamentals on the use of machine learning in stress corrosion crack (SCC) risk analysis or assessment was reviewed. • Current state of the literature on the use of machine learning in stress corrosion cracking were summarized. • Knowledge gaps and challenges of using machine learning in SCC were discussed. • Future perspectives were highlighted. One of the greatest challenges faced by industries today is corrosion and of which, one of the most vital forms is stress corrosion cracking (SCC). It brings highest forms of risks to the industry. Performing risk assessment of stress corrosion cracking is critical to ensure that industrial equipment failure is avoided by employing proper maintenance techniques. With the advancement of digital technology and the fourth industrial revolution called Industrial Internet of Things (IIOT), coupled with the availability of computing power and data, advanced analytical tools like artificial intelligence and machine learning bring powerful algorithms for performing advanced corrosion risk assessment. A perusal of the literature reveals that a review focused on the use of machine learning in corrosion risk assessment of stress corrosion cracking is scarce. So, a comprehensive and up-to-date review on this subject is timely. In this work review we present an overview on the machine learning application in the risk assessment of stress corrosion cracking. First, the current state of the art is briefly summarized. The fundamentals of machine learning algorithms and stress corrosion cracking were presented. Existing knowledge gaps were identified and discussed while the challenges and the future perspectives on the employ of machine learning in corrosion risks assessment of stress corrosion cracking were outlined. [ABSTRACT FROM AUTHOR]

In this study, the influence of minor Ag addition on the microstructure, mechanical and corrosion properties of an Al-Zn-Mg-Cu-Zr (7449) alloy with Zn/Mg ratio of 4 was systematically investigated using various materials characterization techniques, Slow Strain Rate Test (SSRT), Potentiodynamic Polarization (PDP) and Intergranular Corrosion (IGC) measurements. Microstructure characterization by Scanning Electron Microscopy (SEM) and Differential Scanning Calorimetry (DSC) showed that Ag partitioning in the eutectic Mg(Zn,Cu,Al) 2 phase occurs resulting in an increase in its solvus line. After processing to the T4 condition, Ag was partially in solid solution with the excess forming an Ag-rich AlAgZnMgCu phase. Scanning-Transmission Electron Microscopy (STEM) showed evidence of quench-induced η -Mg(Zn,Cu,Al) 2 precipitates at the grain boundaries (GBs) in the T4 condition with ∼3 at.% Ag in the Ag-modified alloy. STEM and Atom Probe Tomography (APT) confirmed that ∼1 at. % Ag was present in both the matrix and GB precipitates in the Ag-modified alloy after T76 aging. Furthermore, the frequently reported decrease in the PFZ width with Ag addition was not observed after T76 aging, with both alloys having a similar PFZ width. Despite higher hardness/strength in the T4 condition with Ag addition, no enhanced age hardening response and alteration of the precipitation kinetics was observed during artificial aging at 121 °C. In fact, Ag addition in a 7xxx alloy with Zn/Mg ratio of 4 was found to be detrimental to mechanical properties, stress corrosion cracking, pitting and IGC resistance after T76 aging, which is attributed to the presence of the Ag-rich AlAgZnMgCu phase. [Display omitted] • Ag addition in 7449 leads to Ag partitioning in eutectic Mg(Zn,Cu,Al) 2 phase and an increase in its solvus temperature. • Ag is partly in solid solution after solution heat treatment. • Ag-rich AlAgZnMgCu phase forms with Ag addition in a 7xxx alloy with Zn/Mg ratio of 4. • Ag addition in a 7xxx alloy with Zn/Mg ratio of 4 did not improve alloy properties. [ABSTRACT FROM AUTHOR]

A passive film serves as a first defense of any material against the attack of a corrosive environment for any material. So, it is essential to understand the parameters affecting the characteristics of the passive film. The present work focused on investigating the effect of tensile load during stress corrosion cracking (SCC) condition on the characteristics of the passive film developed on a TRIP Fe 39 Mn 20 Co 20 Cr 15 Si 5 Al 1 high entropy alloy (HEA) in a 3.5 wt.% NaCl solution at room temperature. A constant load of ∼25% of the yield strength was applied to a flat dog-bone-shaped tensile specimen for 24 h in a 3.5 wt.% NaCl salt environment. For comparison purposes, a specimen with no-load was kept in a salt solution under similar conditions. Electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) techniques were used for passive film characterization. EIS results revealed that the passive film deposited on the no-load and load conditions exhibited a dense and stable structure. However, the passive film deposited on the no-load specimen showed relatively better resistance to corrosion ions. XPS results indicated that the passive film deposited on the no-load and load specimens consisted of Cr rich oxide and hydroxide, forming a monolayer type of passivation film. Nonetheless, the passive film on the no-load specimen exhibited higher concentrations of Cr than the passive film on the loaded specimen. XPS depth profile results showed that the film thickness was relatively greater for the no-load specimen than for the loaded specimen. This study underscores the critical influence of tensile load on the degradation of passive film properties of the HEA. [ABSTRACT FROM AUTHOR]

Herein, the stress corrosion cracking (SCC) susceptibility of duplex (UNS S32205) and austenitic (UNS S31653) stainless steel (SS) reinforcements was evaluated using integrity assessment criteria. Mechanical properties were analyzed and compared by different SCC susceptibility factors. The integrity assessment was conducted applying Cosenza, Creazza, and Ortega ductility criteria, following three different standards (ACI 318-19, ASTM A615, and FIB). A conventional carbon steel (UNS G10080) reinforcement was also evaluated for comparative purposes, whose high residual stress value (>280 MPa) promoted a high corrosion growth rate. Duplex UNS S32205 SS grade showed a significant decrease in elongation, leading to failure after ductility assessment at high chloride concentrations. Fractographic analysis of both SS grades, duplex and austenitic, revealed less than 40% brittle areas at 8 wt.% Cl−, while UNS G10080 had over 85% at 4 wt.% Cl−.

In this work, electrochemical monitoring of stress corrosion cracking (SCC) behavior of a X70 steel in acidic synthetic soil solution during the slow strain rate test (SSRT) was performed by electrochemical noise (EN) using the conventional arrangement of symmetrical electrodes and electrochemical emission spectroscopy (EES) using the asymmetrical arrangement replacing the second working electrode for a platinum micro-cathode. The statistical method, fast Fourier transform, and discrete wavelet transform were used for analyzing the potential and current signals recorded by both arrangements. The results showed that EN arrangement was more effective to detect the crack initiation at a point close to yield strength despite stress-induced asymmetry in one of the electrodes. For the EES arrangement, the micro-cathode had a strong influence on the electrochemical noise of the current and potential under stress conditions. From the transient features, statistical parameters, and wavelet analysis, a discontinuous transgranular SCC mechanism was found. The resistance values obtained by EN measurements had better correlation with the electrochemical impedance spectroscopy results (EIS) than EES measurements. [ABSTRACT FROM AUTHOR]

With the rapid development of the construction of high-pressure, large-diameter and long-distance X80 pipelines in China, Stress Corrosion Cracking (SCC) has become an important factor threatening the safe operation of pipelines. Herein, the key influencing factors of SCC of X80 pipeline steel in soil environment were summarized and analyzed. The influence of Alternating Current (AC) stray current on the SCC behavior of X80 pipeline steel and its influencing mechanism were analyzed, and it was pointed out that the alternating current and the elastic stress can cooperate with each other to jointly promote the anodic dissolution of X80 pipeline steel and destroy the state of dense corrosion product film on the steel surface, further accelerating the corrosion. In addition, the research status of the SCC mechanism of pipeline steel caused by Sulfate Reducing Bacteria (SRB) in soil environment was reviewed. It was concluded that the microbiologically-assisted cracking mechanism of X80 pipeline steel was mainly associated with the physiological activity of bacteria, its metabolites and the formation of biological film. Finally, suggestions on the selection of cathodic protection potential of X80 pipeline steel under SRB were proposed. Further, it is also recommended to include the microbial factors into the SCC evaluation system of pipeline steel. Therefore, the research results can provide theoretical guidance for the design and safety service of high-strength steel pipeline in China.

The welded structural materials of nuclear power plants (NPPs) are susceptible to environmentally-assisted cracking (EAC), represented by stress corrosion cracking (SCC), in prolonged high-temperature and high-pressure water environments, posing a significant threat to plant safety. This study aims to provide a critical review for the crack growth driving force at the tip of SCC in the safe end dissimilar metal welded joint (DMWJ) of NPPs. Firstly, SCC's background, importance, and current research status are introduced. Secondly, a review and analysis are conducted on SCC's initiation and growth stages, focusing on experimental methods, predictive models of crack growth rate, crack tip mechanical states, and influencing factors, clarifying the main achievements and challenges in current experimental and theoretical research. Finally, a method to mitigate crack tip driving force is proposed, followed by an in-depth analysis from a mechanical perspective on the relationship between crack growth driving force and crack growth resistance, highlighting future research trends. This review provides theoretical references and technical support for addressing the issue of SCC in welded structural materials of NPP primary circuit. [ABSTRACT FROM AUTHOR]

Herein, the chloride-induced stress corrosion cracking (SCC) mechanisms of UNS S32205 duplex stainless steel (DSS) reinforcing bars in alkaline and carbonated solutions are studied. Electrochemical monitoring and mechanical properties were tested using linear polarization resistance and electrochemical impedance spectroscopy, coupled with the slow strain rate tensile test (SSRT) to evaluate the SCC behavior and unravel the pit-to-crack mechanisms. Pit initiation and crack morphology were identified by fractographic analysis, which revealed the transgranular (TG) SCC mechanism. HCO3− acidification enhanced the anodic dissolution kinetics, thus promoting a premature pit-to-crack transition, seen by the decrease in the maximum phase angle in the Bode plot at low frequencies (≈ 1 Hz) for the carbonated solution. The crack propagation rate for the carbonated solution increased by over 100% compared to the alkaline solution, coinciding with the lower phase angle from the Bode plots, as well as with the lower charge transfer resistance. Pit initiation was found at the TiN nonmetallic inclusion inside the ferrite phase cleavage facet, which developed TG-SCC.

In this research, the stress corrosion cracking (SCC) behavior of X80 pipeline steel in a Xinzhou soil environment at different temperatures and applied potentials was studied with a slow strain rate test (SSRT), potentiodynamic polarization curve measurements, and scanning electron microscopy (SEM). When a higher anodic potential was applied, anodic dissolution occurred at the crack tip and on the crack wall. The cracking mechanism of X80 steel in Xinzhou soil solution is anodic dissolution (AD). At positive cathodic potentials, X80 steel is under an anodic polarization state at the crack tip and under a cathodic polarization state at the crack wall. The SCC of X80 steel is affected by the combined effects of anodic dissolution (AD) and hydrogen embrittlement (HE). At more negative cathodic potentials, both crack tips and crack walls are under cathodic polarization. The SCC of X80 steel is dominated by hydrogen embrittlement (HE). SCC susceptibility has the same variation trend with potentials at different temperatures. The susceptibility to SCC increases notably as the temperature increases at weak cathodic potentials and open circuit potential due to the effect of temperature on the corrosion potential and the diffusion of atoms. [ABSTRACT FROM AUTHOR]

The paper presents the susceptibility of AE44 magnesium alloy to electrochemical corrosion and stress corrosion cracking (SCC). The evaluation of the intensity of the interaction of the corrosive environment was carried out using the corrosion tests and the Slow Strain Rate Test (SSRT). Corrosion tests performed in 0.1 M Na2SO4 solution (immersion in solution and under cathodic polarization conditions) revealed that the layer of corrosion products was much thicker after immersion test. The results of SSRT showed that the AE44 alloy deformed in the solution was characterized by higher plasticity compared to the alloy deformed in the air after immersion in solution. Moreover, the fractures were characterized by different morphology. In the case of an alloy deformed in the solution under cathodic polarization many microcracks on the fracture were observed, which were not observed in the case of the alloy deformed in the air.

A 3-dimensional (3D) fuel performance analysis program, able to simulate normal operating conditions and accident conditions for PWR fuel behaviors, was developed based on the Multiphysics Object-Oriented Simulation Environment (MOOSE) finite-element framework. By taking fission products swelling, densification and expansion of pellet, thermal and irradiation creep, gap heat transfer, fission gas release, and cladding crack propagation into consideration, detailed fuel behaviors have been simulated in a multiphysics coupling way. Local defects in fuel pellet caused during manufacturing and filling processes known as the missing pellet surface (MPS) can cause abnormal stress distribution of the cladding and it could even lead to cladding failure. Taking Stress Corrosion Cracking (SCC) phenomenon into consideration, a simulation of PWR fuel rodlet that consists of a pellet with an MPS defect and an intact pellet was conducted. The fuel rod has experienced with sorts of events, including normal operating conditions and a high-power ramp event. The simulation results indicated that: 1) The MPS defect affects the temperature and displacement distribution in the vicinity of the MPS defect. When the pellets are in contact with the cladding, the inner surface of the cladding presents a large tensile hoop stress, which accelerates the crack propagation. 2) During the ramp event, the crack propagation rate was higher than that under normal condition and crack length expanded by about 0.1 µm.

In this work, electrochemical monitoring of stress corrosion cracking (SCC) behavior of a X70 steel in acidic synthetic soil solution during the slow strain rate test (SSRT) was performed by electrochemical noise (EN) using the conventional arrangement of symmetrical electrodes and electrochemical emission spectroscopy (EES) using the asymmetrical arrangement replacing the second working electrode for a platinum micro-cathode. The statistical method, fast Fourier transform, and discrete wavelet transform were used for analyzing the potential and current signals recorded by both arrangements. The results showed that EN arrangement was more effective to detect the crack initiation at a point close to yield strength despite stress-induced asymmetry in one of the electrodes. For the EES arrangement, the micro-cathode had a strong influence on the electrochemical noise of the current and potential under stress conditions. From the transient features, statistical parameters, and wavelet analysis, a discontinuous transgranular SCC mechanism was found. The resistance values obtained by EN measurements had better correlation with the electrochemical impedance spectroscopy results (EIS) than EES measurements.

This paper presents a current research trend based on the best papers awarded in 2019 and 2020 by Materials Transactions. The summary includes the 8 papers carefully selected from the articles in the research areas of materials physics, microstructures of materials, mechanics of materials, materials chemistry, materials processing, and engineering materials and their applications. Four out of the 8 best papers are those specially selected for young scientists who are the age of 35 or younger. Here, brief summary is given for the introduction of high quality papers published in Materials Transactions. [ABSTRACT FROM AUTHOR]

• Corrosion coupons bent different angles can simulate the column material under different stress conditions. • The corrosion degree of the coupon with 20° bend is higher than other coupons. • In the study time range, the corrosion rate first decreased, then increased and finally decreased. • In a certain temperature range, the temperature can promote the corrosion rate of 316 L stainless-steel. Stress corrosion is the main factor that results in corrosion and fractures of rectifying columns in the process industries. Stress corrosion of rectifying columns can result in significant economic losses to chemical industries, while also having a major impact on the quality of products produced, particularly polysilicon. This gives rise to the need for research involving stress corrosion of rectifying columns. Corrosion coupons, including those with welds and bends, were used to simulate various stress conditions of stainless steel. For the experiments, a 1.5 wt.% hydrochloric acid and 2.5 wt.% sodium chloride solution was prepared to simulate realistic working conditions for the steel. The experimental methods include static coupon experiment, electrochemical experiment, scanning electron microscope and X-ray diffraction. The corrosion products of the coupons consisted mostly of grey-green materials with loose surface layers and small amounts of black matter. The corrosion products were confirmed to be FeCl 2 and Fe 2 O 3 , and the corrosion degree of the bent 20° coupon was found to be greater than that of other types of coupons. Under low temperature conditions, the corrosion rate of the coupons initially decreased over time before increasing and then decreasing again. At high temperatures, the corrosion rate began to decrease earlier than at low temperatures. The bending tendency of the 20° hanging piece was the greatest and that of the 30° hanging piece was the smallest. Higher temperatures promoted stress corrosion, with increases in temperature resulting in more significant corrosion effects. The results reported herein provide a theoretical basis and technical guidance for important anticorrosion and safety designs for distillation columns to be used in the semiconductor polysilicon rectification process. [ABSTRACT FROM AUTHOR]

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The paper presents the susceptibility of AE44 magnesium alloy to electrochemical corrosion and stress corrosion cracking (SCC). The evaluation of the intensity of the interaction of the corrosive environment was carried out using the corrosion tests and the Slow Strain Rate Test (SSRT). Corrosion tests performed in 0.1 M Na2SO4 solution (immersion in solution and under cathodic polarization conditions) revealed that the layer of corrosion products was much thicker after immersion test. The results of SSRT showed that the AE44 alloy deformed in the solution was characterized by higher plasticity compared to the alloy deformed in the air after immersion in solution. Moreover, the fractures were characterized by different morphology. In the case of an alloy deformed in the solution under cathodic polarization many microcracks on the fracture were observed, which were not observed in the case of the alloy deformed in the air. [ABSTRACT FROM AUTHOR]

The paper describes structure and properties of dissimilar stainless steels welded joints between duplex 2205 and austenitic 316L steels. Investigations were focused on environmentally assisted cracking of welded joints. The susceptibility to stress corrosion cracking (SCC) and hydrogen embrittlement was determined in slow strain rate tests (SSRT) with the strain rate of 2.2 × 10−6 s−1. Chloride-inducted SCC was determined in the 35% boiling water solution of MgCl2 environment at 125°C. Hydrogen assisted SCC tests were performed in synthetic sea water under cathodic polarization condition. It was shown that place of the lowest resistance to chloride stress corrosion cracking is heat affected zone at duplex steel side of dissimilar joins. That phenomenon was connected with undesirable structure of HAZ comprising of large fractions of ferrite grains with acicular austenite phase. Hydrogen assisted SCC tests showed significant reduction in ductility of duplex 2205 steel while austenitic 316L steel remains almost immune to degradation processes. SSR tests of dissimilar welded joints revealed a fracture in the area of austenitic steel.

In the last years, electrochemical noise (EN) has demonstrate that is capable of detect the initiation of cracks during the slow strain rate tests (SSRT). In this research, EN has been used as a tool to detect stress corrosion cracking (SCC) in low carbon steel (X52) exposed to a synthetic soil solution called NS4 at room temperature with pH of 5, 8 and 10. The electrochemical potential and current noise were measured simultaneously during SSRT. Relation between EN and SCC process was analyzed. EN readings of current consisted of transients with high intensity and frequency during all SSRT tests. EN readings of potential at the maximum strength (UTS) and before fracture, increase intensity and amplitude of the transients, attributed to beginning of cracking. Localized index (LI) values indicate a mix corrosion type (general and localized corrosion) during SSRT tests. According to SCC index obtained from mechanical properties, it is clear that X52 steel has low SCC susceptibility. Scanning electron microscopy (SEM) observations were carried out in the fracture surface and longitudinal sections. The specimens tested in NS4 solution with pH 5 were the most likely to present SCC, additionally in this condition a brittle fracture with transgranular appearance was observed.

The environmental performance of 316L grade stainless steel, in the form of tensile specimens containing a single corrosion pit with various aspect ratios, under cyclic loading in aerated chloride solutions is investigated in this study. Results from environmental tests were compared and contrasted with those obtained using finite element analysis (FEA). Fractography of the failed specimens obtained from experiments revealed that fatigue crack initiation took place at the base of the shallow pit. The crack initiation shifted towards the shoulder and the mouth of the pit for pits of increasing depth. This process is well predicted by FEA, as the strain contour maps show that strain is the highest around the centric strip of the pit. However, for shallow pits, local strain is uniformly distributed around that strip but begins to concentrate more towards the shoulder and the mouth region for increasingly deep pits. [ABSTRACT FROM AUTHOR]

A full failure analysis was applied to a set of failed stainless steel (SS) nozzle and sealing disk. The set was taken from a pressure relief valve (PRV) installed on a piping carrying hydrocarbon gas. The investigation included both experimental and numerical analysis. Experimental analysis confirmed the failure mode in the present case to be high-stress-regime transgranular stress corrosion cracking (TGSCC) promoted by susceptible microstructure and the presence of a chloride- and H 2 S-bearing working fluid. Finite element modelling (FEM) was used for the numerical analysis to model the evolution of tensile residual stress associated with the observed SCC. FEM results have shown that the tensile stresses, required for crack initiation and propagation, were associated with the service conditions, especially thermal history, of the nozzle set. FEM results have shown very close (almost exact) agreement with the experimental results obtained in terms of crack directions, relative stress levels and locations of dominance for each type of stress. The present results are thought to be very useful in designing/re-designing similar parts for better performance, under extreme thermal conditions, and for avoiding such failure in future. • FEM was used successfully to accurately model residual stresses. • Local weather conditions can strongly affect parts' thermal history. • SCC was initiated by service-induced residual stresses in 326 SS. • SCC crack morphology is dependent on stress magnitude and direction. [ABSTRACT FROM AUTHOR]

Slow strain rate tests and constant strain corrosion tests were employed to study the effect of pre-strain on stress corrosion cracking behavior and initiation mechanism of E690 steel in simulated marine atmosphere. Results revealed that pre-strain can result in enhancement of both anodic and cathodic reactions of E690 steel in simulated marine atmosphere. Intergranular corrosion and microcracks formed after 4 days of exposure in sulfite-containing marine atmosphere at constant pre-strain, which consequently caused detrimental effects on the mechanical properties and subsequent SCC behavior of E690 steel. The presence of sulfite and high-angle grain boundaries of prior austenite grain boundaries (PAGBs) accounted for the intergranular corrosion and SCC initiation along PAGBs. • The detrimental effect of exposure in marine atmosphere at different pre-strain on subsequent SCC behaviors was revealed. • Intergranular corrosion and microcracks were initiated in sulfite-containing marine atmosphere at constant pre-strain. • The mechanism of intergranular corrosion and SCC initiation along PAGBs was revealed based on EBSD analysis. [ABSTRACT FROM AUTHOR]

The paper examines the effect of deviation in heat treatment due to sudden furnace breakdown and its impact on the stress corrosion cracking (SCC) susceptibility of 17-4 PH stainless steel used in pyro bolts for solid rocket boosters. The SCC susceptibility of the alloy was examined in 3.5% NaCl solution using slow strain rate test. The reduction in ductility was used as a parameter to evaluate the SCC susceptibility. The results indicated that the measured ductility ratios εNaCl/εair of the alloy in both heat-treated conditions were comparable (0.88 and 0.95). Furthermore, the fracture surface examination of the alloy exhibited typical ductile cracking morphology ruling out the environmental cracking susceptibility of the alloy. However, the poor elongation of the altered heat-treated sample was found to be due to the copper precipitation (~ 10 nm) during slow cooling of the alloy during the furnace break down. This was further confirmed by the measured impact toughness and hardness which was found to be less for the altered heat-treated sample. [ABSTRACT FROM AUTHOR]

Highlights • A simulation-informed method for Common Cause Failure (CCF) Analysis is developed. • Physical failure mechanisms are explicitly incorporated by simulation models. • Simulation-based CCF data is integrated with existing CCF data by Bayesian method. • Probabilistic Validation characterizes and propagates epistemic uncertainty. Abstract Common Cause Failures (CCFs) are critical risk contributors in complex technological systems as they challenge multiple redundant systems simultaneously. To improve the CCF analysis in Probabilistic Risk Assessment (PRA), this research develops the Simulation-Informed Probabilistic Methodology (S-IPM) for CCFs. This new methodology utilizes simulation models of physical failure mechanisms to capture underlying causalities and to generate simulation-based data for the CCF probability estimation. To operationalize the S-IPM in PRA, a computational algorithm is developed that generates simulation-based estimates of CCF parameters and, using the Bayesian approach, integrates them with the data-driven CCF parameters (if relevant data available) from the existing PRA. This computational algorithm is equipped with the Probabilistic Validation that quantifies the degree of confidence in the simulation-based parameter estimates by characterizing and propagating epistemic uncertainty in multiple levels of analysis. The S-IPM can (i) provide more realistic CCF probability estimates by considering CCF data generated from simulations; (ii) reflect as-built, as-operated plant conditions, considering the updates in design, operational, and maintenance policies; and (iii) contribute to more effective prevention and mitigation of CCFs by providing "cause-specific" quantitative risk insights. The paper shows a case study that applies S-IPM to the CCFs of emergency service water pumps of NPPs. [ABSTRACT FROM AUTHOR]

This study examines the stress corrosion cracking (SCC) behavior of the Fe 39 Mn 20 Co 20 Cr 15 Si 5 Al 1 (at.%) high entropy alloy in a salt solution at room temperature. The research employs slow strain-rate tensile tests and advanced analytical techniques, such as electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM), to understand the SCC behavior. Results show that the alloy has a high susceptibility to SCC. The TEM analysis supports a slip-step dissolution model for SCC. The EBSD results suggest that cracks form at boundaries between martensite and austenite phases and propagate through interphase and inter-variant boundaries. Reducing such boundaries may mitigate the alloy's SCC susceptibility. • SCC study of TRIP HEA with predominately HCP ε – martensite phase. • SCC behavior of the HEA dependent of the strain-rate. • SCC susceptibility index (I SCC) very high at 10−6 s−1 strain rate (55%). • Transgranular type of brittle fracture for the specimen showing highest I SCC. • Crack propagation along HCP-FCC interphase and HCP-HCP phase boundaries. [ABSTRACT FROM AUTHOR]