Stress Corrosion Cracking Behavior Research Articles

Effects of H2S/HS− on Stress Corrosion Cracking Behavior of X100 Pipeline Steel Under Simulated Sulfate-Reducing Bacteria Metabolite Conditions

The effect of H2S/HS−, which simulates the main metabolites of sulfate-reducing bacteria (SRB), on the electrochemical and stress corrosion cracking (SCC) behaviors of X100 steel was investigated in a near-neutral solution. The results showed that different H2S/HS− contents mainly affected the cathodic process of X100 electrochemical corrosion. As the concentration of H2S/HS− increased, the corrosion potential was shifted negatively, the corrosion current density was considerably increased, and the corrosion rate was linearly increased. Different rust layers with shifting structures were formed under different conditions and had different effects on electrochemical behaviors. However, sulfide mainly promoted local corrosion processes. With the synergistic effects of stress and H2S/HS−, SCC susceptibility was considerably enhanced. The accelerated process of hydrogen evolution by sulfide was crucial in enhancing SCC processes. In brief, the trace H2S/HS− generated by SRB metabolites played a positive role in promoting SCC.

Influence of Erbium, Cerium on the Stress Corrosion Cracking Behavior of AZ91 Alloy in Humid Atmosphere

AZ91 magnesium alloys modified by Er and Ce are fabricated (referred to as AZErCe) and their stress corrosion cracking (SCC) behaviors are studied by slow strain rate tensile (SSRT) method in air, humid atmosphere with and without chloride. The addition of Er and Ce promotes the formation of Al3Er and Al11Ce3 phase and reduces both the size and the volume fraction of β‐phase. AZErCe possess improved corrosion resistance and passivation characteristic compared to AZ91 due to the reduced micro‐galvanic corrosion and the more protective films. SSRT tests demonstrate that the joint addition of Er and Ce effectively improve the SCC resistance of AZ91 alloy. In particular, the representative fractography of AZErCe exhibits lesser effect of hydrogen embrittlement than AZ91. The improved SCC resistance of AZErCe can be ascribed to the presence of Er and Ce, which alleviate corrosion of Mg matrix and thus weaken the effect of hydrogen embrittlement on SCC resistance.

Study on Corrosion and Stress Corrosion Cracking Behaviors of AZ31 Alloy in Sodium Sulfate Solution

The potentiodynamic polarization test and slow strain rate tensile test were carried out in 3.5 wt.% Na2SO4 solution with different pH values (2, 7, and 12). It was found that the SCC susceptibility of AZ31 magnesium alloy in 3.5 wt.% Na2SO4 solution was deteriorated significantly with the decreasing pH. This was consistent with the electrochemical properties. There were filiform corrosion forms on the specimen surface after slow strain rate tensile test in 3.5 wt.% Na2SO4 solution, which indicated the characteristics of general corrosion. Moreover, there were multiple stress corrosion crack initiation sources. The SCC fracture of AZ31 magnesium alloy in air was a mix type, while it was cleavage fracture in 3.5 wt.% Na2SO4 solution.

Stress Corrosion Cracking Behavior of X80 Pipeline Steel in Acid Soil Environment with SRB

Self-designed experimental device was adopted to ensure the normal growth of sulphate-reducing bacteria (SRB) in sterile simulated Yingtan soil solution. Stress corrosion cracking (SCC) behavior of X80 pipeline steel in simulated acid soil environment was investigated by electrochemical impedance spectroscopy, slow strain rate test, and scanning electron microscope. Results show that the presence of SRB could promote stress corrosion cracking susceptibility. In a growth cycle, polarization resistance first presents a decrease and subsequently an increase, which is inversely proportional to the quantities of SRB. At 8 days of growth, SRB reach their largest quantity of 1.42 × 103 cells/g. The corrosion behavior is most serious at this time point, and the SCC mechanism is hydrogen embrittlement. In other SRB growth stages, the SCC mechanism of X80 steel is anodic dissolution. With the increasing SRB quantities, X80 steel is largely prone to SCC behavior, and the effect of hydrogen is considerably obvious.

Effects of Nitrogen and Tensile Direction on Stress Corrosion Cracking Susceptibility of Ni-Free FeCrMnC-Based Duplex Stainless Steels.

Stress corrosion cracking (SCC) behavior of Ni-free duplex stainless steels containing N and C (Febalance-19Cr-8Mn-0.25C-(0.03, 0.21)N, in wt %) was investigated by using a slow strain rate test (SSRT) in air and aqueous NaCl solution with different tensile directions, including parallel (longitudinal) and perpendicular (transverse) to the rolling direction. It was found that alloying N was effective in increasing the resistance to SCC, while it was higher along the longitudinal direction than the transverse direction. The SCC susceptibility of the two alloys was assessed based on the electrochemical resistance to pitting corrosion, the corrosion morphology, and the fractographic analysis.

Stress corrosion cracking behavior of PH13-8Mo stainless steel in Cl– solutions

The stress corrosion cracking (SCC) behavior of PH13-8Mo precipitation hardening stainless steel (PHSS) in neutral NaCl solutions was investigated through slow-strain-rate tensile (SSRT) test at various applied potentials. Fracture morphology, elongation ratio, and percentage reduction of area were measured to evaluate the SCC susceptibility. A critical concentration of 1.0 mol/L neutral NaCl existed for SCC of PH13-8Mo steel. Significant SCC emerged when the applied potential was more negative than —0.15 VSCE, and the SCC behavior was controlled by an anodic dissolution (AD) process. When the applied potential was lower than —0.55 VSCE, an obvious hydrogen-fracture morphology was observed, which indicated that the SCC behavior was controlled by hydrogen-induced cracking (HIC). Between —0.15 and —0.35 VSCE, the applied potential exceeded the equilibrium hydrogen evolution potential in neutral NaCl solutions and the crack tips were of electrochemical origin in the anodic region; thus, the SCC process was dominated by the AD mechanism.

Investigating the influence of hydrogen on stress corrosion cracking of 2205 duplex stainless steel in sulfuric acid by electrochemical impedance spectroscopy

AbstractAs a nondestructive and sensitive method, electrochemical impedance spectroscopy (EIS) can be used to investigate the passivation and breakdown of passive films on steel. In this study, EIS, combined with slow strain rate test and scanning electron microscopy, was employed to study the stress corrosion cracking (SCC) behavior of 2205 duplex stainless steel in 0.5 m sulfuric acid solution under hydrogen-charging conditions. Results showed that the corrosion resistance of passive film on the hydrogen-charged specimen was lower than that for the specimen with no hydrogen charge. Hydrogen-induced cracking was evident after the specimens had been charged for 24 h. The phase shift in EIS, calculated from frequencies between 0.1 and 10 Hz, could be used to monitor the SCC process.

SCC of 2304 Duplex Stainless Steel—Microstructure, Residual Stress and Surface Grinding Effects

The influence of surface grinding and microstructure on chloride induced stress corrosion cracking (SCC) behavior of 2304 duplex stainless steel has been investigated. Grinding operations were performed both parallel and perpendicular to the rolling direction of the material. SCC tests were conducted in boiling magnesium chloride according to ASTM G36; specimens were exposed both without external loading and with varied levels of four-point bend loading. Residual stresses were measured on selected specimens before and after exposure using the X-ray diffraction technique. In addition, in-situ surface stress measurements subjected to four-point bend loading were performed to evaluate the deviation between the actual applied loading and the calculated values according to ASTM G39. Micro-cracks, initiated by grinding induced surface tensile residual stresses, were observed for all the ground specimens but not on the as-delivered surfaces. Loading transverse to the rolling direction of the material increased the susceptibility to chloride induced SCC. Grinding induced tensile residual stresses and micro-notches in the as-ground surface topography were also detrimental.

The Effect of Loading Orientation on the Stress Corrosion Cracking of Al-Mg Alloys

The effect of loading orientation (S-L versus T-L) on intergranular stress corrosion cracking (IGSCC) behavior was assessed in AA5083 and AA5456 in two tempers (-H116, -H131) at nitric acid mass loss test (NAMLT) levels of 24 mg/cm2 and 40 mg/cm2. Regardless of temper or composition, loading in the T-L orientation demonstrated reduced susceptibility to IGSCC as a result of delamination toughening caused by fissure propagation in the L-T plane. Electron backscatter detection analysis confirmed these fissures to be intergranular, and the fissure size/density increased in plane strain constraint conditions toward the center of the specimen. Occurrence of these out-of-plane fissures was validated by testing on NAMLT of 10 mg/cm2 and 67 mg/cm2 AA5456-H116, although delamination propagation occurred only under full immersion in 0.6 M NaCl, and not testing (fatigue or slow rising displacement) conducted in moist air. These delamination phenomena are understood further through application of a hydrogen-enhanced d...

Effect of alternating current on stress corrosion cracking behavior and mechanism of X80 pipeline steel in near-neutral solution

The influence of alternating current (AC) density on stress corrosion cracking (SCC)behavior and the mechanism of X80 pipeline steel was investigated in NS4 near-neutral solution by slow strain rate tensile tests (SSRT), surface analysis techniques, data acquisition technique, and electrochemical measurements. Results showed that the SCC susceptibility of X80 pipeline steel was improved with the increasing of AC density, and the SCC mechanism was collectively controlled by anodic dissolution (AD) and hydrogen embrittlement (HE). When the AC density was below 10 A m−2, the corrosion enhanced because of a vibrating effect. However, when the AC density was no less than 30 A m−2, SCC susceptibility enhanced because of the hydrogen evolution reaction. With regard to potential acquisition, only a very small percentage about 1.5%–2% of AC was involved acting as faradaic current, which resulted in hydrogen evolution reaction and then improved the SCC susceptibility.

Nucleation behavior of intergranular stress corrosion cracking in austenitic stainless steel

Nucleation behavior of intergranular stress corrosion cracking in austenitic stainless steel

Comparative study on the stress corrosion cracking of X70 pipeline steel in simulated shallow and deep sea environments

The stress corrosion cracking (SCC) behavior of X70 steel in simulated shallow and deep sea environments was studied using potentiodynamic polarization measurement, a slow strain rate tensile (SSRT) test and scanning electron microscopy (SEM). The results indicate that the predominant cathodic reaction changes from an oxygen reduction reaction to the hydrogen evolution reaction as the dissolved oxygen (DO) content decreases. In the simulated deep sea environment, the SCC susceptibility of X70 steel decreased first, reached its lowest point at 15MPa and then increased as the simulated sea hydrostatic pressure (HP) further increased. This is consistent with the regularity for the change of the cathodic hydrogen evolution reaction current density iH at Ecorr, which indicates that the HP may influence the SCC susceptibility of X70 steel by changing the permeated hydrogen concentration.

Effect of laser shock peening on the stress corrosion cracking of AZ31B magnesium alloy in a simulated body fluid

Stress corrosion cracking (SCC) behavior of AZ31B Magnesium (Mg) alloy with and without Laser Shock Peening (LSP) was studied using slow strain rate tension (SSRT) method in a simulated body fluid (SBF) at 36.5±0.5°C. The effects of two-sided simultaneous LSP on microstructure, residual stress, surface roughness and electrochemical property of AZ31B samples were investigated by using optical microscopy, X-ray diffraction (XRD) method, true color material confocal microscopy, transmission electron microscopy (TEM) and electrochemical polarization experiment. The experimental results show that based on the optimal laser processing parameters, surface nanocrystallization could be induced in the AZ31B surface layer. Comparing with the original samples, the corrosion potential increased 131mV, the corrosion current density decreased by 85.4% and the SCC susceptibility index (ISCC) decreased by 47.5% after LSP. Based on the experimental observations, the improvement mechanism of SCC resistance for AZ31B with LSP was also analysed and revealed.

Influence of Changes in Pressure and Temperature of Supercritical Water on the Susceptibility to Stress Corrosion Cracking of 316L Austenitic Stainless Steel

The supercritical water reactor (SCWR) is one of the Generation IV designs. The SCWR is characterized by its high efficiency, low waste production, and simple design. Despite the suitable properties of supercritical water as a coolant, its physicochemical properties change sharply with pressure and temperature in the supercritical region. For this reason, there are many doubts about how changes in these variables affect the behavior of the materials to general corrosion or to specific types of corrosion such as stress corrosion cracking (SCC). Austenitic stainless steels are candidate materials to build the SCWR due to their optimum behavior in the light water reactors (LWRs). Nevertheless, their behavior under the SCWR conditions is not well known. First, the objective of this work was to study the SCC behavior of austenitic stainless steel 316 type L in deaerated supercritical water at 400°C/25 MPa and 30 MPa and 500°C/25 MPa to determine how variations in pressure and temperature influence its behavior with regard to SCC and to make progress in the understanding of mechanisms involved in SCC processes in this environment. Second, the oxide layer formed at 400°C/30 MPa/<10 ppb O2 was analyzed to gain some insight into these processes.

Effect of Heat Treatment on Stress Corrosion Cracking Behavior and Electrochemical Characteristic of Welded Ti-6Al-4V Alloy during Slow Strain Rate Test

Effect of Heat Treatment on Stress Corrosion Cracking Behavior and Electrochemical Characteristic of Welded Ti-6Al-4V Alloy during Slow Strain Rate Test

Effects of strain rate on stress corrosion of S355 steel in 3.5% NaCl solutions

The stress corrosion of S355 steel in 3.5% NaCl solution under the different strain rates was analyzed with the slow strain rate test (SSRT), the stress corrosion cracking (SCC) behaviors of S355 steel under the different strain rates in the solution were investigated, and the fracture morphologies and compositions of corrosion products under the different strain rates were analyzed with scanning electron microscopy (SEM) and energy dispersive spectrometerry (EDS), respectively. The experimental results show that the SCC sensitivity index is the highest when the strain rate is 2×10-6, and the medium corrosion is the main reason resulting in the highest SCC sensitivity index. The SCC sensitivity index is the least when the strain rate is 5×10-6, and the stress is the main reason resulting in the stress corrosion. The SCC sensitivity index is the middle when the strain rate is 9×10-6, the interaction of stress and medium is the stress corrosion fracture mechanism.

POTENTIAL MITIGATION STRATEGIES FOR PREVENTING STRESS CORROSION CRACKING FAILURES IN HIGH-BURNUP CANDU FUEL

Potential mitigation strategies for preventing stress corrosion cracking (SCC) failures in CANDU fuel cladding that are based on lessons learned on both domestic and international fronts are discussed in this paper. Although SCC failures have not been a major concern in CANDU reactors in recent decades, they may resurface at higher burnup for conventional fuels or with nonconventional fuels that are currently being investigated, such as MOX or thoria-based fuels. The motivation of this work is to provide the foundation for considering possible remedies for SCC failures. Three candidate remedies are discussed, namely improved fabrication methods for fuel appendages, barrier-liner cladding, and fuel doping. In support of this effort, recent advances in experimental characterization methods are described—methods that have been successfully used in non-nuclear materials that can be used to further elucidate SCC behaviour in CANDU fuel. The overall objective is to outline a path forward for characterizing material behaviour as an essential part of investigating remedies to SCC failure. This will allow increased fuel discharge burnup, maximum linear power, and plant manoeuvrability, while maintaining a high degree of reliability.

Effect of plastic deformation on the electrochemical and stress corrosion cracking behavior of X70 steel in near-neutral pH environment

This work investigated the effect of plastic deformation on the electrochemical and stress corrosion cracking (SCC) behavior of X70 steel in near-neutral pH environment. The deformation-induced increase in electrochemical activity, dislocation density and heterogeneity, and surface roughness accelerated the corrosion, especially the cathodic reactions. Hydrogen absorption and permeation into the steel is promoted by the plastic deformation, resulting in the high hydrogen content of the pre-deformed steels. Moreover, the SCC susceptibility increases with plastic elongation, which is attributed to the enhanced anodic dissolution and hydrogen absorption.

Stress Corrosion Cracking Behavior of 4.19%Zn-1.34%Mg (A7N01S-T5) Aluminum Alloy Welded Joints

The fracture toughness behavior of Al-Zn-Mg alloy, A7N01S-T5, welded joints was investigated using three points bending test with the J integral approach. The microstructures of the welded joints were examined using optical microscopy, microhardness, and transmission electron microscopy. The heat affected zone (HAZ) had the best crack propagation resistance, and the weld zone (WZ) and base metal (BM) behaved similarly. The stress corrosion cracking (SCC) behavior of the welded joints was investigated under a constant loading condition. The threshold stress intensity factor of SCC and the cracks’ propagation rate were tested. The microstructure of the fracture was examined using optical microscope and scanning electron microscope. The results showed that both the BM and the HAZ were susceptible to SCC and the HAZ was smaller than the BM, but no cracks were detected in the WZ. A greater amount of H+ and a higher concentration of Zn and Mg accumulated at the crack front tips, which led to the SCC resistance ...

Effects of Applied Strain and Sensitization on SCC Behavior of 304 Stainless Steel in Atmospheric Corrosion Environments

Austenitic stainless steels have relatively good corrosion resistance due to the formation of a Cr-rich passive film. However, in atmospheric corrosion environments near seashore, austenitic stainless steels can suffer from localized attacks such as pitting corrosion and crevice corrosion. This is due to the formation of thin water layers containing high concentration of chloride ions on the stainless steels. In addition, when the steels are subjected to tensile stress or deformation, stress corrosion cracking (SCC) can occur from pits. Since it is well-know that sensitization can enhance SCC susceptibility of austenitic stainless steels, it is needed to clarify the effect of deformation and sensitization on the SCC of the steels in atmospheric corrosion environments. In this study, crack initiation and propagation behavior of sensitized 304 stainless steels was investigated under a MgCl2 solution droplet. The experimental results demonstrated that cracks were initiated from pits by applying plastic deformation. It was confirmed that hydrogen evolution was observed during propagation of the cracks. In the presentation, SCC mechanism of sensitized 304 stainless steels in atmospheric corrosion environments will be discussed.