Stress Corrosion Cracking Behavior Research Articles

Effect of cold work and slow strain rate on 321SS stress corrosion cracking in abnormal conditions of simulated PWR primary environment

Abstract In this paper, stress corrosion cracking (SCC) behavior of 0%, 5%, 10% cold-worked (CW) 321 stainless steel (321 SS) in abnormal conditions of simulated pressurized water reactor (PWR) primary water was studied at two different slow strain rates of 4.2 × 10−6, 4.2 × 10−7. The experimental results show that with the increase of the degree of cold work, the internal grain of the sample is refined. The slip zone and deformation twins occur inside some grains. The SCC sensitivity of the strain rate of 4.2 × 10−7 S−1 is higher than the strain rate of 4.2 × 10−6 S−1. And the higher the degree of cold work, the higher the SCC sensitivity of the sample. Dynamic strain aging (DSA) occurs at 321 SS with different cold work degrees with a slow strain rate of 4.2 × 10−7 S−1. DSA makes the tensile zone near the fracture of 5% CW and 10% CW samples have higher vacancy defect density, which promotes the initiation and expansion of SCC crack.

Stress Corrosion Cracking Behavior of Alloy 600 Coupled to Magnetite under High-Temperature Caustic Conditions.

This study aims to investigate and explain the magnetite-accelerated stress corrosion cracking phenomenon of Alloy 600 under caustic conditions, based on the electrochemical behavior. After the SCC test that lasted for 300 h, no cracks were observed in any of the magnetite-free specimens, whereas cracks with a depth of 150 to 280 μm were generated in all the magnetite-deposited specimens. Furthermore, the electrochemical behavior of magnetite and Alloy 600 demonstrated that Alloy 600 behaved as an anode in the coupling system with magnetite. In this coupling system, the electrochemical potential of Alloy 600 can be shifted into the range potentially susceptible to stress corrosion cracking.

Effect of grain structure on the stress corrosion cracking (SCC) behavior of an as-extruded Mg-Zn-Zr alloy

Through investigating and comparing the microstructure and stress corrosion cracking (SCC) behavior of an as-extruded Mg-6.2Zn-0.8Zr (in wt.%) alloy before and after solid solution treatment (T4), the effects of grain structure on the SCC resistance and cracking modes have been disclosed. Slow strain rate testing (SSRT) results demonstrated that the SCC resistance decreased with the increased fraction of coarse grains. Failure analysis indicated that for the finely grain-structured samples, the cracking mode was dominated by the intergranular cracking. For the “bi-modal” grain-structured samples, the cracking mode was intergranular/transgranular mixed type. For the coarsely grain-structured samples, the cracking mode was transgranular.

Electrochemical characteristic and stress corrosion behavior of API X70 high-strength pipeline steel under a simulated disbonded coating in an artificial seawater environment

The electrochemical and stress corrosion cracking (SCC) behavior of API X70 pipeline steel under a disbonded coating in artificial seawater was studied using in situ electrochemical measurements and ex situ slow strain rate tensile (SSRT) tests. Results indicated that the electrochemical behavior differs significantly with distance from defect opening. SCC mechanism of X70 steel under the disbonded coating was typically controlled by the synergistic action of anodic dissolution (AD) and the effect of hydrogen, and the susceptibility to SCC at the bottom of the crevice was much higher than that close to the defect opening. Furthermore, the effect of hydrogen on the SCC process is discussed in particular using a quantitative relationship between the cathodic current density and SCC susceptibility.

Stress corrosion cracking behavior of warm forged 316L stainless steel at different orientations

Stress corrosion cracking (SCC) behavior of ∼20% warm forged 316L stainless steel (SS) round bar was evaluated for different cracking orientations relative to the applied deformation in hydrogenated and oxygenated high purity water at 325 °C. Different SCC crack growth rates (CGRs) obtained at three orientations demonstrates that the L-R orientation where cracking occurred in the plane of deformation has the highest SCC susceptibility, while the C-L orientation where cracking was oriented to run along the forging direction has the lowest SCC susceptibility. The anisotropic cracking behavior of warm forged 316L SS at different orientations, which is prominent in hydrogenated water, depends highly on the distribution of lamellar plastic strains that are produced during deformation in different planes.

Influence of different heat-affected zone microstructures on the stress corrosion behavior and mechanism of high-strength low-alloy steel in a sulfurated marine atmosphere

The stress corrosion cracking (SCC) behavior and mechanism of the simulated heat-affected zone (HAZ) of high-strength low-alloy (HSLA) steel in a sulfurated marine atmosphere were surveyed in detail using electrochemical measurements and slow strain rate tensile (SSRT) tests combined with microstructure analysis. The SCC of the simulated HAZs is controlled by both anodic dissolution (AD) and hydrogen embrittlement (HE), which are attributed to the synergistic effect of Cl− and SO42−, as Cl−-induced localized dissolution causes microcrack initiation, and SO42--catalyzed acid regeneration facilitates microcrack propagation. The intercritical HAZ and fine-grained HAZ present high crack numbers because of the high amount of prior austenite grain boundaries (PAGBs), lath bainite boundaries (LBBs), and martensite/austenite (M/A) constituents, which act as preferential sites for hydrogen trapping and crack initiation. However, coarse-grained HAZ exhibits the highest SCC susceptibility because of the coarse PAGBs, wide lath bainites (LBs), and high local dislocation density, which promote crack propagation.

Magnetite-accelerated stress corrosion cracking of alloy 600 in water containing 100 ppm lead oxide at 315 °C

The purpose of this work is to verify the effect of magnetite coupled with Alloy 600 on stress corrosion cracking (SCC) behavior in water containing 100 ppm PbO at 315 °C. SCC tests were conducted using U-bend specimens partially covered with magnetite, simulating a condition wherein magnetite was deposited on steam generator tubes. The maximum crack depths of the Alloy 600 specimens coupled with magnetite were 20–68% greater than those of the uncoupled specimens for a given test time. The coupling of magnetite to Alloy 600 led to the fast growth of oxide films, resulting in the formation of relatively Cr-depleted inner oxides with defects. The corrosion potential of Alloy 600 was 90 mV lower than that of magnetite at 80 °C, indicating that the corrosion of Alloy 600 could be stimulated by galvanic coupling with magnetite. The accelerated stress corrosion and altered film properties were discussed from the viewpoint of a galvanic coupling effect.

Effect of non-conventional heat treatment of API X60 pipeline steel on corrosion resistance and stress corrosion cracking susceptibility

PurposeThe purpose of this paper is to study the effect of heat treatment (HT) applied to an API X60 steel in corrosion resistance and stress corrosion cracking (SCC) susceptibility through slow strain rate tests (SSRT) in NS4 solution and congenital water (CW) to assess external and internal SCC, respectively.Design/methodology/approachAPI X60 steel was heat treated at a temperature of 1,200°C for 30 min followed by water quenching. Specimens from this steel were machined according to NACE TM 198. SSRT were performed in a constant extension rate tests (CERT) machine at room temperature at a strain rate of 1 × 10–6s–1. For this purpose, a glass cell was used. Corrosion behavior was evaluated through polarization curves (PCs).FindingsThe SCC index obtained from SSRT indicates that the steel heat treated could be susceptible to SCC in CW and NS4 solution; the mechanism of SCC was hydrogen embrittlement. Thus, CW may promote the SCC phenomenon in pipelines. HT improves the steel corrosion resistance. Higher corrosion rate (CR) was observed when the steel is exposed to CW. The corrosion process in X60 steel shows that the oxidation reaction in the anodic branch corresponds to an activation process, and the cathode branches reveal a diffusion process.Originality/valueThe purpose of the heat treatment applied to X60 steel was to generate a microstructure of acicular ferrite to improve the corrosion resistance and SCC behavior.

Effect of Heat Treatment Anomaly on the Stress Corrosion Cracking Behavior of 17-4 PH Martensitic Stainless Steel

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 eNaCl/eair 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.

Stress Corrosion Cracking Behavior of Tungsten Inert Gas Welded Age-Hardenable AA6061 Alloy

The effects of two temper conditions (T4 and T6 heat treatments) upon the stress corrosion cracking (SCC) of AA6061 plates have been investigated in this work. AA6061 alloys were double-side-welded by the tungsten inert gas (TIG) welding method. SCC behavior of both the as-welded and as-received alloys was reported. Optical microscopy (OM) and scanning electron microscopy (SEM) were used to determine the precipitate structure of the thermal-altered zones and the base metal (BM), and also the hardness variations were examined using microhardness testing (Vickers hardness). The small-size precipitate structures in the T6 tempered alloy and the coarser precipitate structures in the T4 tempered alloy were found by microstructural investigations. As a result, T4 temper heat treatment of this alloy considerably reduced its susceptibility to stress corrosion cracks due to relatively coarse and more separate precipitate morphology. In welded specimens, SCC failure occurred in the area between the heat-affected zone (HAZ) and the base metal. Stress corrosion resistance in the fusion zone was strong in both temper conditions. The aim of this work was to obtain the effects of heat treatment and welding on SCC behavior of the age-hardenable aluminum alloy. The authors conclude that a deep insight into the SCC resistance of AA6061 alloy indicates the precipitate particle distributions and they are the key point for AA6061 alloy joints in chloride solution.

Stress corrosion cracking behavior of X90 pipeline steel and its weld joint at different applied potentials in near-neutral solutions

X90 pipeline steel is a new generation of pipeline steel developed after X80 and X100 pipeline steels, and it is now a new research hotspot at home. In order to thoroughly study the effect of applied potential on the soil stress corrosion cracking (SCC) behavior of X90 pipeline steel, we investigated the SCC behaviors of base metal and weld joint samples in the straight-weld pipe of X90 pipeline steel at different applied potentials in near-neutral solution using electrochemical measurements methods and slow strain rate testing (SSRT). Besides, the fracture surfaces were observed through scanning electron microscope (SEM) and the mechanisms of the corrosion cracking behaviors were analyzed. And the following research results were obtained. First, the polarization curves of the base metal and weld joint samples in the NS4 solution present the typical characteristics of anodic dissolution but no activation–passivation phenomenon happens. Second, in the NS4 solution, the base metal and weld joint samples present SCC sensitivity. The SCC sensitivity indicator which is expressed by yield loss percentage elongation and yield loss percentage elongation area decreases firstly and then increases with the negative increase of the applied potential, and the SCC sensitivity of weld joint is higher than that of base metal. Third, there are three mechanisms on the SCC behaviors of base metal and weld joint samples, i.e., anodic dissolution mechanism when the applied potential is open circuit potential (EOCP), anodic dissolution and hydrogen embrittlement mechanism when the applied potential is −850 mV, and hydrogen embrittlement mechanism when the applied potential is −1000 mV and −1200 mV. It is concluded that the research results can provide a technical support and theoretical basis for the large-scale application of X90 pipeline steel.

Effect of strain rate and sulfate reducing bacteria on stress corrosion cracking behaviour of X70 pipeline steel in simulated sea mud solution

In order to reduce the damage to the operation of oil and gas pipelines，the stress corrosion cracking (SCC) behavior of X70 pipeline steel in the South China Sea mud simulation solution under different strain rates and diverse growth days of sulfate-reducing bacteria (SRB) was investigated through slow strain rate test, scanning electron microscopy, and energy-dispersive spectroscopy. Results showed that the sensitivity of SCC initially increased and then decreased with the increase of strain rate when the number of SRB growth days was fixed. When the strain rates were 1 × 10−6 s−1 and 4 × 10−6 s−1, greater SRB growth days indicate more sensitivity of the SCC. When the strain rate increased to 7.5 × 10−6 s−1, the degree of the SCC in metals under the aseptic solution was small, and serious SCC would occur when SRB existed in the environment. The SCC sensitivity was maximum under the synergistic effect of strain rate of 4 × 10−6 s−1 and SRB number of 5.7 × 106 cells/ml.

Sulfide Stress Corrosion Cracking Behavior of G105 and S135 High-Strength Drill Pipe Steels in H2S Environment

Slow strain rate testing was employed to investigate the sulfide stress corrosion cracking (SSCC) behavior of low-carbon high-strength drill pipe steels (G105 and S135) in the simulated drilling environment containing H2S. Results reveal that both G105 and S135 steels have a high SSCC susceptibility in the simulated drilling environment containing H2S. In the range of experimental slow strain rate, the SSCC sensitivity of drill pipe steel increases with the decrease in slow strain rate, and the ductility and fracture properties of drill pipe steels also decrease obviously. With the increase in the steel strength, the SSCC sensitivity of the drill pipe steel increases, and the S135 drill pipe steel has higher SSCC sensitivity than G105. There is no obvious plastic deformation on the fracture surface of G105 and S135 steels in H2S solution. The cracks of fracture sprout on the surface of the specimen, the instantaneous fracture zone is in the middle, and the fracture can be divided into the cracking and the final fracture zone. The SSCC mechanisms of two drill pipe steels are hydrogen embrittlement. The hydrogen enters the steel and reduces the binding force of the iron atom, resulting in cleavage fracture.

HISCC behavior of SUS301L-MT stainless steel laser-arc hybrid welding joints

The hydrogen-induced stress corrosion cracking (HISCC) behavior of SUS301L-MT stainless steel laser-arc hybrid welding (LAHW) joints was investigated using slow strain rate tensile (SSRT) method in 3.5 wt.% NaCl solution under different cathodic potentials. With the negative shift of applied potentials from open circle potential (OCP) to −1400 mV[Formula: see text], the HISCC susceptibility index ([Formula: see text]) decreased from 0.15 (OCP) to 0.06 (−400 mV[Formula: see text]), then increased to 0.28 (−1400 mV[Formula: see text]). The specimens tested in air and under OCP to −800 mV ruptured in weld metal zone with ductile features of dimples. While with the potential turned more negative, the specimens ruptured in base metal zone with brittle features of transgranular cleave in martensite, intergranular failure and secondary cracks [Chen et al., Int. J. Adv. Manuf. Technol. 73, 1695 (2014)].

Feature of stress corrosion cracking of degraded gas pipeline steels

Stress corrosion cracking (SCC) of steels can reduce the structural integrity of gas pipelines. To simulate in-service degradation of pipeline steels in laboratory the method of accelerated degradation consisted in subjecting specimens to electrolytic hydrogenation, to loading up the certain plastic deformation and heating of specimen at 250°C was recently developed. The purpose of this paper was to analyse mechanical and SCC behaviour of in-service and in-laboratory degraded gas pipeline steels and to reveal some fractographic features of SCC. Three pipeline steels of the different strength (17H1S, which is equivalent of API X52, API X60 and API X70) were investigated. The characteristics of the as-received pipeline steels with different strength were compared with the properties of pipeline steels after in-service and in-laboratory degradation. An influence of the NS4 solution on SCC resistance of 17H1S and API X60 steels in the as-received state and after the accelerated degradation, using slow strain rate tension method, was analysed. The noticeable decrease of plasticity for 17H1S and API X60 steels after long-term operation was shown. Deep microdelaminations revealed in the central part of fracture surfaces for the operated steels can be considered as the signs of dissipated damaging in the metal caused by texture and hydrogen absorbed by metal. Comparison of the SCC tests results showed that the characteristics of both steels in the as-received state were insignificantly changed under the influence of the environment. At the same time, the degraded steels were characterized by a high sensitivity to SCC. It was shown fractographically that it associated with cracking along interfaces of ferrite and pearlite grains with secondary deep intergranular cracks formation and also by delamination between ferrite and cementite inside pearlite grains. The similar fracture mechanism at SCC tests was revealed for near the outer surface of the specimens and in the central part of the fracture surfaces of in-laboratory degraded specimens. These results demonstrated the key role of hydrogen during SCC and in-bulk cracking as well.

Hydrogen atoms on the SCC behavior of SUS301L-MT stainless steel laser-arc hybrid welded joints

Laser-arc hybrid welding (LAHW) process has been applied for excellent manufacturing the new generation subway vehicles underframe using cold rolled SUS301 L stainless steel. However, the effects of hydrogen atoms on the stress corrosion cracking (SCC) behavior are still unclear, which is probably a latent risk for the application. Here, in combination with the microstructures and fracture morphologies analysis, the effects of hydrogen atoms on SCC behavior of SUS301L-MT (MT = 15% cold rolling, middle tensile) stainless steel LAHW welded joints and the base metal (BM) was investigated by slow strain rate tensile (SSRT) method during applied cathode potentials on the specimen in 3.5 wt.% NaCl solution. The results indicated that the SUS301L-MT ASS LAHW welded joints exhibited lower SCC susceptibility than that of BM, particularly at very negative cathode potential, −1200 mV and −1400 mV, the SCC susceptibility of the welded joints (～0.3) is 2 times lower than that of BM (～0.6), due to the high solubility of hydrogen atoms and low hydrogen embrittlement (HE) susceptibility of weld metal (WM). We hope this study can help to assist LAHW process widely apply for the manufacturing of new generation subway vehicles underframe as well as other welding structures.

Stress corrosion cracking behavior of 310S stainless steel in supercritical water at different temperature

The stress corrosion cracking (SCC) behavior and tensile properties of 310S stainless steel were studied by slow strain rate tensile (SSRT) tests, which were carried out in oxygenated supercritical water at the temperature of 400, 550, and 620 °C, respectively. The distribution of chemical composition of oxide, tensile properties, fracture morphology of the materials were analyzed for evaluating the SCC susceptibility of 310S stainless steel, respectively. The results show that both the elongation and tensile strength decreased significantly with the increase of the temperature, implying that a higher temperature may lead to a higher SCC susceptibility. The remarkable changes of the morphology of the fracture surface and gauge surface of 310S stainless steel were observed at different temperatures, that is, from an entire ductile fracture at lower temperature to a brittle fracture at higher temperature. The temperature has significant effects on morphologies and thickness. Oxides with double layer were observed. TEM analysis revealed that the inner oxide layer is composed of Cr and O, and Ni‐enrichment can be observed to segregate at the metal‐oxide interface.

HCl Çözeltisinde AISI 304 Paslanmaz Çeliğinin Gerilim Korozyon Çatlaması Davranışı

Korozif ortamlarda calisan metalik malzemeler, ozellikle dusuk karbonlu paslanmaz celikler farkli korozif ortamlarda gerilim korozyon catlagi davranisi bakimindan ciddi sonuclar dogurabilmektedir. Bu calisma AISI 304 kalite paslanmaz celik uzerinde bir U-bukum ile gerilim yaratilarak farkli seyreltilerdeki asidik ortamlarda meydana gelen gerilim korozyon catlamasi (GKC) davranisini incelemeyi amaclamistir. Bu ortamlarda farkli surelerde bekletilen numunelerin yuzey puruzluluk degerleri ve agirlik kayiplari da gozlemlenmistir. Korozyon davranisi metalografik incelemeler ve agirlik kayiplari ile tespit edilmistir. Gerilim korozyon catlagi %10 HCl iceren cozelti icerisinde 288. saatte meydana gelmeye baslarken %15 HCl iceren cozelti icerisinde 144. saatte meydana gelmistir. Bu da HCl oraninin artmasinin GKC mekanizmasini hizlandirdigi anlamina gelmektedir. AISI 304 ostenitik paslanmaz celik malzemesinde HCl cozeltisi icerisinde GKC mekanizmasinin tane sinirlari yaninda U-bukumden kaynaklanan soguk deformasyon sonucu olusan kayma bantlarinda da gerceklestigi gozlemlenmistir. Ayrica korozif ortam icerisinde bekletilen tum numunelerde agirlik kaybi ve yuzey puruzlulugunun arttigi gorulmustur.

Effect of loading mode on fracture behavior of CrNiMoV steel welded joint in simulated environment of low pressure nuclear steam turbine

Stress corrosion cracking (SCC) behaviors of 30Cr2Ni4MoV welded joint in simulated environment of low pressure nuclear steam turbine were addressed with different fracture positions in the welded joint by constant loading test (CLT) and slow strain rate test (SSRT). The fracture of the welded joint happened near the fusion line which was ascribed to the interaction between stress and galvanic effect for CLT, while in welded metal with the weakest strength for SSRT. The mismatch between galvanic corrosion and strength of welded joint determined the fracture location and SCC sensitivity of the welded joint when the two different loading modes were applied.

Synergistic Effect of AC and Cl- on Stress Corrosion Cracking Behavior of X80 Pipeline Steel in Alkaline Environment

Synergistic Effect of AC and Cl- on Stress Corrosion Cracking Behavior of X80 Pipeline Steel in Alkaline Environment