Review of stress corrosion cracking of pipeline steels in "low" and "high" pH solutions

This paper reviews the current understanding of the mechanisms of stress corrosion cracking of pipeline steels. The similarities, the differences and the influencing factors are considered for the high pH stress corrosion cracking caused by a concentrated bicarbonate-carbonate solution, and for the low pH stress corrosion cracking due to a diluter solution. For high pH stress corrosion cracking, it is well accepted that the mechanism involves anodic dissolution for crack initiation and propagation. In contrast, it has been suggested that the low pH stress corrosion cracking is associated with the dissolution of the crack tip and sides, accompanied by the ingress of hydrogen into the pipeline steel. But the precise influence of hydrogen on the mechanism needs to be further studied. (C) 2003 Kluwer Academic Publishers.

Environmental influence on the stress corrosion cracking of rock bolts

In order to understand rock bolt Stress Corrosion Cracking (SCC), a series of experiments have been performed in Linearly Increasing Stress Test (LIST) apparatus. One series of experiments determined the threshold stress of various bolt metallurgies (900 MPa for Steel A, and 800 MPa for Steel B and C). The high values of threshold stress suggest that SCC begins in rock bolts when they are sheared by moving rock strata. Typical crack velocity values have been measured to be 2.5 x 10(-8) m s(-1), indicating that there is not much benefit for rock bolt steel of higher fracture toughness. Another series of experiments were performed to understand the environmental conditions causing SCC of steel A and galvanised Steel A rock bolt steel. SCC only occurred for environmental conditions for which produce hydrogen on the sample surface, leading to hydrogen embrittlement and SCC. Fracture surfaces of LIST samples failed by SCC were found to display the same fracture regions as fracture surfaces of rock bolts failed in service by SCC: Tearing Topography Surface (TTS), Corrugated Irregular Surface (CIS), quasi Micro Void Coalescence (qMVC) and Fast Fracture Surface (FFS). Water chemistry analysis were carried out on samples collected from various Australian mines in order to compare laboratory electrolyte conditions to those found in underground mines.

Material influence on the stress corrosion cracking of rock bolts

Rock bolt stress corrosion cracking (SCC) has been investigated using the linearly increasing stress test (LIST). One series of experiments determined the threshold stress of various bolt metallurgies (900 MPa for 1355AXRC, and 800 MPa for MAC and MA840B steels). The high values of threshold stress suggest that SCC begins in rock bolts when they are sheared by moving rock strata. SCC only occurred for environmental conditions which produce hydrogen on the sample surface, leading to hydrogen embrittlement and SCC. Different threshold potentials were determined for a range of metallurgies. Cold work was shown to increase the resistance of the steel to SCC. Rock bolt rib geometry does not have a direct impact on the SCC resistance properties of the bolt, although the process by which the ribs are produced can introduce tensile stresses into the bolt which lower its resistance to SCC. (C) 2004 Elsevier Ltd. All rights reserved.

A study on stress corrosion cracking and hydrogen embrittlement of AZ31 magnesium alloy

The stress corrosion cracking (SCC) behavior and pre-exposure embrittlement of AZ31 magnesium alloy have been studied by slow strain rate tensile (SSRT) tests in this paper. It is showed that AZ31 sheet material is susceptible to SCC in distilled water, ASTM D1.387 solution, 0.01 M NaCl and 0.1 M NaCl solution. The AZ31 magnesium alloy also becomes embrittled if pre-exposed to 0.01 M NaCl solution prior to tensile testing. The degree of embrittlement increased with increasing the pre-exposure time, It is proposed that both the pre-exposure embrittlement and SCC were due to hydrogen which reduces the cohesive strength. i,e,. hydrogen embrittlement, (c) 2005 Elsevier B.V. All rights reserved.

Assaigs Stress Corrosion Cracking (SCC)

En aquest projecte es presenta la realització d’un sistema d’assaig de la corrosió sota tensió (stress corrosion cracking, SCC) i un estudi de l’efecte de l’SCC sobre dos acers d’eina per matrius d’estampació en calent. L’SCC és la formació i propagació d’esquerdes en un material degut a la interacció de tres factors: un medi corrosiu, un material susceptible i una tensió estàtica aplicada. Aquestes esquerdes són difícils de detectar i poden provocar fallades catastròfiques inesperades i, en concret, s’ha detectat aquest fenomen en matrius refrigerades d’estampació en calent. Es pretén dissenyar i construir un dispositiu d’assaig SCC per tal d’utilitzar-lo per l’estudi dels materials 1.2367 i 1.2343 en condicions d’aigua de xarxa, aigua destil·lada i inhibidor. Aquests assaigs es realitzen a les temperatures de 40 i 80ºC ja que un estudi previ ha simulat les condicions de temperatura als canals de refrigeració de les matrius d’estampació en calent i s’ha vist que aquestes són les temperatures assolides. La raó d’estudiar aquests materials és perquè són dos acers d’eina per treball en calent convencionals, usats en l’àmbit de les matrius refrigerades d’estampació en calent i en general en processos de conformat en calent (forja, moldeig). S’estudia el comportament a tracció d’aquests materials en aquestes condicions comparant-lo amb el mateix assaig però en condicions en aire, i s’avaluen les diferències en la tensió màxima, la ductilitat, el mecanisme de fractura o l’esquerdament sofert. Es fa un estudi fractogràfic de les mostres mitjançant microscòpia electrònica de rastreig (SEM) i un estudi de les superfícies laterals i del secondary cracking mitjançant microscòpia òptica. Es comparen els diferents resultats obtinguts i es determina en quines condicions s’ha desenvolupat SCC i en quines no, en quina intensitat i quines opcions hi ha per evitar-lo.

Slow Strain Rate Testing and Stress Corrosion Cracking of Ultra-Fine Grained and Conventional Al-Mg Alloy

Stress corrosion cracking susceptibility was investigated for an ultra-fine grained (UFG) AI-7.5Mg alloy and a conventional 5083 H111 alloy in natural seawater using slow strain rate testing (SSRT) at very slow strain rates between 1E(-5) s(-1), 1E(-6) s(-1) and 1E(-7) s(-1). The UFG Al-7.5Mg alloy was produced by cryomilling, while the 5083 H111 alloy is considered as a wrought manufactured product. The response of tensile properties to strain rate was analyzed and compared. Negative strain rate sensitivity was observed for both materials in terms of the elongation to failure. However, the UFG alloy displayed strain rate sensitivity in relation to strength while the conventional alloy was relatively strain rate insensitive. The mechanical behavior of the conventional 5083 alloy was attributed to dynamic strain aging (DSA) and delayed pit propagation while the performance of the UFG alloy was related to a diffusion-mediated stress relaxation mechanism that successfully delayed crack initiation events, counteracted by exfoliation and pitting which enhanced crack initiation. (C) 2014 Elsevier B.V. All rights reserved.

Stress corrosion cracking control measures /

Includes bibliographical references and index.

Stress corrosion cracking and hydrogen embrittlement of an Al-Zn-Mg-Cu alloy

The age hardening, stress corrosion cracking (SCC) and hydrogen embrittlement (HE) of an Al-Zn-Mg-Cu 7175 alloy were investigated experimentally. There were two peak-aged states during ageing. For ageing at 413 K, the strength of the second peak-aged state was slightly higher than that of the first one, whereas the SCC susceptibility was lower, indicating that it is possible to heat treat 7175 to high strength and simultaneously to have high SCC resistance. The SCC susceptibility increased with increasing Mg segregation at the grain boundaries. Hydrogen embrittlement (HE) increased with increased hydrogen charging and decreased with increasing ageing time for the same hydrogen charging conditions. Computer simulations were carried out of (a) the Mg grain boundary segregation using the embedded atom method and (b) the effect of Mg and H segregation on the grain boundary strength using a quasi-chemical approach. The simulations showed that (a) Mg grain boundary segregation in Al-Zn-Mg-Cu alloys is spontaneous, (b) Mg segregation decreases the grain boundary strength, and (c) H embrittles the grain boundary more seriously than does Mg. Therefore, the SCC mechanism of Al-Zn-Mg Cu alloys is attributed to the combination of HE and Mg segregation induced grain boundary embrittlement. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Analysis of service stress corrosion cracking in a natural gas transmission pipeline, active or dormant?

Stress corrosion cracks (SCC) had been found in a natural gas transmission pipeline during a dig-up and inspection program. The question was raised as to whether the SCC was active or dormant. This paper describes the resultant investigation to determine if a particular service crack was actively growing. The strategy adopted was to assess the appearance of the fracture surface of the service crack and to compare with expectations from laboratory specimens with active SCC. The conclusions from this study are as follows. To judge whether a crack in the service pipe is active or dormant, it is reasonable to compare the very crack tip of the service crack and a fresh crack in a laboratory sample. If the crack tip of the active laboratory sample is similar to that of the service pipe, it means the crack in the service pipe is likely to be active. From the comparison of the crack tip between the service pipe and the laboratory samples, it appears likely that the cracks in the samples extracted from service were most likely to have been active intergranular stress corrosion cracks. (C) 2003 Elsevier Ltd. All rights reserved.

A critical review of the stress corrosion cracking (SCC) of magnesium alloys

This review aims to provide a foundation for the safe and effective use of magnesium (Mg) alloys, including practical guidelines for the service use of Mg alloys in the atmosphere and/or in contact with aqueous solutions. This is to provide support for the rapidly increasing use of Mg in industrial applications, particularly in the automobile industry. These guidelines should be firmly based on a critical analysis of our knowledge of SCC based on (1) service experience, (2) laboratory testing and (3) understanding of the mechanism of SCC, as well as based on an understanding of the Mg corrosion mechanism.

Atom probe field ion microscope measurements of carbon segregation at an a:a grain boundary and service failures by intergranular stress corrosion cracking

This work reports on a critical measurement to understand the intergranular stress corrosion cracking (IGSCC) of pipeline steels: the atom probe field ion microscope (APFIM) measurement of the carbon concentration at a grain boundary (GB). The APFIM measurement was related to the microstructure and to IGSCC observations. The APFIM indicated that the GB carbon concentration of X70 was similar to 10 at% or less, which correlated with a high resistance to IGSCC for X70. (C) 2005 Elsevier Ltd. All rights reserved.

Stress corrosion cracking and hydrogen diffusion in magnesium

Evaluation of recent data for hydrogen (H) diffusion in magnesium (Mg) yielded a new equation for the diffusion coefficient of H in Mg. This indicates that there can be significant H transport ahead of a stress corrosion crack in Mg at ambient temperature and that H may be involved in the mechanism of stress corrosion cracking in Mg.

Modelling of Stress-Corrosion Cracking by Using Peridynamics

Acknowledgement The authors are grateful to Prof. Siegfried Schmauder and Prof. Erdogan Madenci for the useful discussions that occurred throughout the realization of this study and acknowledge the Defence Science and Technology Laboratory (DSTL) for the financial support. A special thanks go to the anonymous reviewers, whose time and contribution have been highly appreciated. Results were obtained using the EPSRC funded ARCHIE-WeSt High Performance Computer (www.archie-west.ac.uk). EPSRC grant no. EP/K000586/1.