Stress Corrosion Cracking Behavior Research Articles

Effects of Minor Sr Addition on Biocorrosion and Stress Corrosion Cracking of As-Cast Mg-4Zn Alloys

Microstructure, biocorrosion, and stress corrosion cracking (SCC) behavior of as-cast Mg-4Zn-xSr alloys (x ≤ 0.4, in mass%) are studied by scanning electron microscopy, immersion testing, slow strain rate tensile testing, etc. A minor Sr addition (≤0.2%) in Mg-4Zn alloy can reduce the average corrosion rate and the corrosion current density in Hank’s solution, resulting from grain refinement, dispersion of the smaller secondary phase particles, and the more-protective corrosion product film. Thus, a minor Sr addition (≤0.2%) can improve both strength and plasticity of the Mg-4Zn alloy without increasing the SCC susceptibility, and the Mg-4Zn-0.1Sr alloy exhibits the best comprehensive properties.

Finite element simulation of stress corrosion cracking in austenitic stainless steel using modified Lemaitre damage model

The material failure due to stress corrosion cracking (SCC) is widely observed phenomena in many of the industrial applications. Many-a-times it causes drastic loss to the organisation. In the present work, the study is performed to evaluate the stress corrosion cracking (SCC) behaviour of SS304. The Lemaitre damage model is widely employed to evaluate the failure or damage of the engineering materials. In the present work, the Lemaitre damage model is modified by incorporating the effect of temperature and Chloride concentration to analyse SCC by recording the initiation of cracks over a period of time. The finite element analysis is performed over a rectangular specimen of SS304 by applying tensile loading under different testing temperatures and Chloride concentrations. It is observed that with the increase in temperature and Chloride concentration the number of cracks initiated increases and the time required for crack initiation decreases. Further, it is found that the effect of temperature is prominent for the initiation of crack during SCC in comparison to the Chloride concentration within the testing range.

Stress Corrosion Cracking Behavior of 2024 and 7075 High-Strength Aluminum Alloys in a Simulated Marine Atmosphere Contaminated with SO2

The stress corrosion cracking (SCC) of high-strength 2024-T351 and 7075-T651 aluminum alloys in simulated marine atmospheric medium containing HSO3− was investigated. The results showed that the presence of HSO3− could significantly accelerate the corrosion process of 2024-T351 and 7075-T651 high-strength aluminum alloy. This process was attributed to the enhanced anodic dissolution and hydrogen embrittlement caused by the HSO3−. The SCC susceptibility showed an increasing trend in both of aluminum alloys with increasing HSO3− concentration. Meanwhile, the hydrogen generated by HSO3− was shown to change the failure mode of these two aluminum alloys.

Stress Corrosion Cracking Behavior of Cold Worked 316L Stainless Steel in Chloride Environment

Stress Corrosion Cracking Behavior of Cold Worked 316L Stainless Steel in Chloride Environment

Stress corrosion cracking behavior of rusted X100 steel under the combined action of Cl− and HSO3− in a wet–dry cycle environment

X100 steel is an important material used to construct marine pipelines; hence, understanding its stress corrosion cracking (SCC) behavior is important. Herein, we investigated the SCC mechanism of rusted X100 steel in a wet–dry cycle environment at various Cl− and HSO3− contents. Slow strain-rate testing revealed brittle fracture features at high HSO3− content, while electrochemical studies showed that HSO3− promotes increased cathode current density that contributes to stress corrosion cracking. We conclude that SCC cracking is initiated at pits formed by anodic dissolution, while the hydrogen-evolution mechanism dominates in a high HSO3− concentration environment.

An Investigation on Corrosion and Stress Corrosion Cracking initiation of a Ferritic Stainless Steel in a Tertiary Amine Solution

The present study focused on stress corrosion cracking (SCC) and corrosion behavior of ferritic stainless steel (grade 430) in activated methyl diethanolamine (aMDEA) solution, which is classified as a tertiary amine. In this regard, cyclic polarization and U-bend tests were performed in CO2 loaded aMDEA with different concentrations at 25 and 70 °C to observe corrosion behavior and also the possibility of crack initiation. Based on the obtained results, it was found that the corrosion rate increased in concentrated amine solutions. Also, by increasing temperature from 25 to 70 °C both corrosion rate and susceptibility to SCC initiation were intensified. Increment of amine concentration and also increase in temperature led to more absorption of CO2, generating a more acidic solution. Overall it could be stated that while for the grade 430 stainless steel investigated in this study corrosion and cracking was observed Therefore it could be concluded that in amine-containing environments this steel is not a very suitable alternative for carbon steels, which are commonly used in these environments.

Investigation of Stress Corrosion Cracking Behaviour of Mg-Al-Zn Alloys in Different pH Environments by SSRT Method

AbstractIn this study, stress corrosion behaviors of AZ31, AZ61 and AZ91 Mg alloys which contain different amounts of Al were investigated under acidic, basic and neutral environments having chloride ions using Slow Strain Rate Test (SSRT) method. Stress corrosion indexes (ISCC), ultimate tensile strength (UTS) and elongation of AZ31, AZ61, and AZ91 Mg alloys were determined and compared. Slow strain rate test showed that three Mg alloys in basic environments were the least stress corrosion susceptible, while the most stress corrosion susceptible occurred in acidic environments. Also, it has been shown that the stress corrosion indexes of AZ91 Mg alloys are less than AZ31 and AZ61 Mg alloys in all environments. UTS and elongation of AZ61 Mg alloys were higher than those of AZ31 and AZ91 in all media. The fracture of surface images also examined in the scanning electron microscope (SEM) and both intergranular stress corrosion cracking (IGSCC) and transgranular stress corrosion cracking (TGSCC) were observed in all three alloys.

Effect of cathodic potential on stress corrosion cracking behavior of different heat-affected zone microstructures of E690 steel in artificial seawater

In this work, the stress corrosion cracking (SCC) behavior of E690 steel base metal (BM) and different heat-affected zone (HAZ) microstructures, i.e., coarse grain HAZ (CGHAZ), fine grain HAZ (FGHAZ), and intercritical HAZ (ICHAZ), was investigated at different cathodic potentials in artificial seawater by slow strain rate tensile tests, scanning electron microscopy and electron back-scattered diffraction measurements. The results show that the HAZ microstructures and BM exhibit different SCC susceptibilities: FGHAZ < ICHAZ < BM < CGHAZ, which are controlled by anodic dissolution (AD) at the open circuit potential. With the cathodic potential equaling to −750 mV, the SCC susceptibility of the four microstructures increases because of the synergistic effect of AD and weak hydrogen embrittlement (HE). At -850 mV, AD is inhibited, and the SCC susceptibility of BM decreases, while the SCC susceptibility of the HAZ microstructures increases. At a potential below -850 mV, the SCC susceptibility of the four microstructures gradually increases because of the augment of HE, and the SCC susceptibility of the HAZ microstructures is higher than that of BM. The distinction reveals that the HAZ microstructures have the greater HE susceptibility than BM.

Effect of AC Current Density on the Stress Corrosion Cracking Behavior and Mechanism of E690 High-Strength Steel in Simulated Seawater

In this work, we studied the impact of alternating current (AC) density on the stress corrosion cracking (SCC) behavior and mechanism of E690 high-strength steel in simulated seawater with electrochemical measurements, U-bend immersion tests and slow strain rate tensile tests. Results demonstrate that AC enhances both anodic and cathodic processes, especially localized anodic dissolution and hydrogen evolution, which manifests as the increase in icorr with AC current density rising. Therefore, AC leads to higher SCC susceptibility. Accordingly, SCC is dominated by anodic dissolution (AD) at low AC current density while in a mixed control of AD and hydrogen embrittlement (HE) at high AC current density as a result of increasing hydrogen concentration. Besides, 50 A/m2 corresponds to the threshold hydrogen concentration of the “hydrogen-induced plasticity to HE” transformation, which is due to the different interactions of dislocation and hydrogen.

Investigation of the stress corrosion cracking behavior in annealed 5083 aluminum alloy sheets with different texture types

Al–Mg alloys are commonly employed for anti-corrosion parts in marine and rail vehicles. However, the corrosion resistance of these alloys is affected by the alloy microstructure. In this study, 5083 aluminum alloy sheets with different recrystallized textures (a low-intensity texture, a cube-based texture, and a brass-based texture) were obtained by cold rolling and annealing. The stress corrosion cracking and short crack propagation behavior were investigated based on the microstructural characterization, intergranular corrosion, electrochemical corrosion, and slow strain rate testing. The results showed that the tested samples exhibited large differences in stress corrosion properties, although they had a similar resistance to intergranular corrosion. The sample dominated by the brass texture exhibited the best resistance to stress corrosion cracking (SCC) with an ISSRT of 11.7%, while the sample with the low-intensity texture exhibited the worst resistance to SCC with an ISSRT of 29.7%. Moreover, the stress corrosion crack in the sample dominated by the brass texture propagated along a more tortuous path. The crack was deflected at brass texture grains, which was attributed to the combined effects of the relatively large twist angle between the grain boundaries of brass grains and neighboring grains and the low grain boundary energy configuration of {011} orientation grains.

Effect of Cr and N on Stress Corrosion Cracking Behavior of Fe-18Mn Steel

High-Mn steels developed for offshore industries require good resistance to stress corrosion cracking (SCC) in seawater. Elements like Cr and N are often added to improve the resistance to SCC. In this study, the SCC behavior of Fe18Mn3Cr0.1N and Fe19Mn19Cr0.6N steels in artificial seawater was examined. Slow strain rate tests were conducted at a nominal strain rate of 10-6/sec in air and artificial seawater under anodic and cathodic applied potentials. The tensile ductility drop in artificial seawater was compared to air and evaluated as the resistance to SCC. It was found that both specimens showed intergranular cracking in artificial seawater under both anodic and cathodic applied potentials. The intergranular SCC was more severe under anodic applied potential than cathodic applied potential. However the sensitivity to SCC in artificial seawater was substantially reduced in Fe19Mn19Cr0.6N specimen with higher Cr and N content, as compared to the Fe18Mn3Cr0.1N specimen under both applied potentials. Potentiodynamic tests in artificial seawater showed an increase in pitting corrosion potential, rather than corrosion potential, with increasing Cr and N content in high-Mn steel. The SCC behavior of high-Mn steels with different Cr and N contents was discussed based on micrographic and fractographic observations. Key words: stress corrosion cracking, high-Mn steel, artificial seawater

Effects of Nb on stress corrosion cracking of high-strength low-alloy steel in simulated seawater

In this study, simulated heat-affected zone (HAZ) of Nb-free and Nb-bearing steel were obtained, and SEM, TEM, and slow strain rate tensile (SSRT) tests were performed to investigate the effect of Nb on the stress corrosion cracking (SCC) behavior of high-strength low-alloy (HLSA) steel in simulated seawater with or without hydrogen charging. The addition of Nb significantly refined the grains and uniformed the microstructure of HLSA. Nb hardly affected the SCC susceptibility of BM and HAZ without hydrogen-charging. However, after charging with 10 mA cm−2, the SCC resistance of Nb-bearing steel, especially the coarse grain HAZ (CGHAZ) improved drastically, and the process of crack initiation and propagation was inhibited owing to the hydrogen trap function of NbC precipitates.

Enhancement of stress corrosion cracking of AZ31 magnesium alloy in simulated body fluid thanks to cryogenic machining

Magnesium and its alloys have recently attracted great attention as potential materials for the manufacture of biodegradable implants. Unfortunately, their inadequate resistance to the simultaneous action of corrosion and mechanical stresses in the human body have hampered their use as implant materials. This work aims at evaluating the Stress Corrosion Cracking (SCC) susceptibility of the AZ31 Mg alloy after being machined under cryogenic cooling. The SCC behaviour was evaluated by means of Slow Strain Rate Tests (SSRTs) in Simulated Body Fluid (SBF) at 37 °C. Prior to testing, a full characterization of the machined surface integrity, including microstructural observations, residual stress, nano-hardness measurements and surface texture analysis was carried out together with the assessment of the corrosion properties through potentiodynamic polarization curves. In addition, the morphology of the fracture surfaces after SSRTs was analysed by means of 3D optical profiler and Scanning Electron Microscopy (SEM). The improved corrosion resistance due to the increased extension of the nano-surface layer and to the compressive residual stresses represents the reason of the reduced SCC susceptibility of cryogenically machined AZ31 samples as compared to dry machined ones.

Characterization of internal and intergranular oxidation in Alloy 690 exposed to simulated PWR primary water and its implications with regard to stress corrosion cracking

Oxidation testing of Ni-base Alloy 690 was conducted in simulated PWR primary water, and the internal and intergranular (IG) oxidation layers were systematically characterized by analytical transmission electron microscopy to obtain insight into its IG stress corrosion cracking (IGSCC) resistance and behavior. The internal oxidation layer consisted of upper NixFe1-xCr2O4 and innermost Cr2O3. Each internal oxidation layer had a crystallographic orientation relationship with the Alloy 690 matrix, indicating that the layers formed through solid-state reactions between inward diffusing oxygen and the alloying elements. Strong evidence that the Cr2O3 layer formed through the outward grain boundary diffusion of Cr was found, leaving severe Cr depletion along the grain boundary with a steep composition gradient toward the surface. The innermost Cr2O3 layer had a continuous and compact band-shaped morphology around the surface grain boundary. This Cr2O3 layer was revealed to be protective of the inward grain boundary diffusion of oxygen from the surface and therefore responsible for the prevention of grain boundaries from IG oxidation. IG Cr carbides suppressed the internal and IG oxidation further. The key findings obtained in this work may present the main reason for the high resistance of Alloy 690 to IGSCC under PWR normal operating conditions.

Elucidating the role of microstructural modification on stress corrosion cracking of biodegradable Mg4Zn alloy in simulated body fluid.

This paper investigates the effect of microstructure modification by heat treatment on stress corrosion cracking (SCC) behavior of Mg4Zn alloy in simulated body fluid (SBF). Mg4Zn alloy in as cast, solution heat treated and peak aged conditions was susceptible to SCC in SBF when strained at 3.6 × 10-6 s-1. SCC index based on fracture energy is least for solutionized alloy (0.84), while 0.88 for as cast and peak aged alloys. Fractographic analysis indicates predominantly intergranular SCC for solution treated alloy initiated by anodic dissolution near grain boundaries. As cast and peak aged alloy shows mainly transgranular failure due to hydrogen embrittlement adjacent to secondary phase particles.

Dynamic stress corrosion cracking in silicon crystal

We investigated, experimentally, the stress corrosion cracking (SCC) phenomenon in dynamic cracks propagating on two low energy cleavage systems (LECSs) of silicon crystal, (111)[ $$11\,\bar{{2}}$$ ] and (110)[ $$1\,\bar{{1}}\,0$$ ], under air and under Ar at atmospheric pressure. We used our high resolution Coefficients of Thermal Expansion Mismatch (CTEM) method to initiate and propagate the cracks. An important variable in this investigation was the gradient of the energy release rate (ERR) flow to the crack front for unit length of crack advance, $$dG_{0}/da$$ , denoted $$\varTheta $$ , in units of $$\hbox {J}/\hbox {m}^{2}/\hbox {mm}$$ . The CTEM method is capable of manipulating the value of $$\varTheta $$ . When loaded by low ERR gradient, e.g., when $$\varTheta <0.5\hbox { J}/\hbox {m}^{2}/\hbox {mm}$$ , in air, a complex and diverse SCC behavior was revealed; the cleavage energy strongly depends on $$\varTheta $$ , the environment and crystallographic structure. For higher $$\varTheta $$ , the cleavage energy is higher than that at vacuum and remains constant during crack propagation. We further show that at $$\varTheta \,0.5\hbox { J}/\hbox {m}^{2}/\hbox {mm}$$ , the SCC mechanisms vanish for both LECSs, and the cracks initiate and propagate at cleavage energy higher than that in vacuum, or the Griffith barrier of $$2\gamma _{\mathrm{s}}$$ , twice the free surface energy of the cleavage plane. This investigation suggests that the large scatter existing in the literature for the experimental cleavage energies of the current LECSs of silicon crystal and the still existing debate regarding the susceptibility of silicon crystal to SCC, is caused by the different value of $$\varTheta $$ in the various past experiments. We further suggest that $$\varTheta $$ should be stated when discussing the quasi static and dynamic cleavage energy of brittle crystals.

Microstructural evolution and corrosion behavior of friction stir processed fine‐grained AZ80 Mg alloy

AbstractFriction stir processing (FSP) and subsequent aging heat treatment were used to modify the microstructure of AZ80 magnesium alloy. The influence of FSP and aging heat treatment on the corrosion behavior was systematically studied by using potentiodynamic polarization, immersion, and slow strain rate tensile tests. The results revealed that FSP led to grain refinement, rapid dissolution of β‐phase, and the deflection of c‐axis from transverse direction (TD) and processing direction (PD) by approximately 55° and 25°, respectively, improving the static corrosion and stress corrosion cracking (SCC) resistance. The aging heat treatment rendered a little influence on the grain size and slightly affected the grain orientation. The content of β‐phase in FSP‐5 and FSP‐24 samples was 8.1 and 21.8 wt.%, respectively. Static corrosion and SCC resistance of FSP‐5 and FSP‐24 samples were lower than those of the FSP samples. Compared with FSP‐5 sample, the amount of β‐phase and the proportion of Al2O3 increased in FSP‐24 sample, leading to enhanced static corrosion and SCC resistance. SCC behavior was controlled by anodic dissolution, whereas the presence of hydrogen accelerated the SCC.

Enhanced Stress Corrosion Cracking Resistance of Ultrafine-Grained Cu-Cr-Zr Alloy Fabricated via Equal-Channel Angular Pressing

The microstructure evolution and stress corrosion cracking (SCC) behaviors of ultrafine-grained (UFG) Cu-Cr-Zr alloys processed by equal-channel angular pressing (ECAP) and coarse-grain (CG) Cu-Cr-Zr alloys within NaNO2 solution were systematically investigated in the current study. After deformation by eight ECAP passes, the grain size was refined to ~200 nm. The slow strain rate tensile (SSRT) tests showed that the ultimate tensile strength (UTS) of CG samples in solution was slightly lower than that in the air, and the elongation was decreased from 57.3% to 52.6%. In contrast, both the UTS and elongation of UFG samples in air and solution were almost identical. In NaNO2 solution, the CG fracture surface showed an obvious dissolution, microvoids, and minor cracks, while the surface of the UFG fracture was relatively smooth. The resistance of UFG samples to SCC could be significantly enhanced compared with CG samples. The grain boundary volume fraction of UFG alloy was dramatically increased, which reduced the formation of pitting corrosion. In addition, the uniform distribution of Cr particles also improved the corrosion resistance of UFG alloys.

Effect of Cl− Concentration on the SCC Behavior of 13Cr Stainless Steel in High-Pressure CO2 Environment

An effect of Cl− concentration on the stress corrosion cracking (SCC) behavior of 13Cr stainless steel was investigated by employing electrochemical measurements and the slow strain rate tensile tests. These tests were conducted in various solutions with different concentrations of NaCl at 90 °C under 3 MPa CO2 with 3 MPa N2. The results indicate that the passive film of the specimen formed in the 10% NaCl solution has the best protective effect on the matrix. The SCC susceptibility does not increase with increasing the chloride ion concentration, the lowest SCC susceptibility occurs when the NaCl concentration is 10%, and the specimens show higher SCC susceptibility in the 5% NaCl and 20% NaCl solutions.

A study on the stress corrosion cracking susceptibility of friction stir welded Ti-6Al-4V alloy joints

The stress corrosion cracking (SCC) susceptibility of a friction stir welded (FSW) Ti-6Al-4V alloy was assessed through the slow strain rate tensile (SSRT) examinations in air and 3.5% NaCl solution at three temperatures of 25 °C, 37 °C and 80 °C. SSRT results showed that FSW deteriorated the SCC behavior of Ti-6Al-4V in all tested conditions. The fractography of the fractured specimens by SEM revealed that a dimpled fracture mode predominated in the failure of the heat affected zone of the FSWed specimens. Also, it was found that increasing the test temperature resulted in decreasing the fracture toughness of the base and weld metals. The microhardness examination of the welded specimen indicated that the stir zone (SZ) showed higher hardness values than that of the heat affected zone (HAZ). This behavior was attributed to the formation of finer and coarser grains in the SZ and HAZ, respectively.