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• The addition of Mn improves the strength of traditional 3Ni weathering steel. • Considerable SCC resistance of novel high strength Ni-advanced steel. • Hydrogen embrittlement resistance was enhanced by Ni and Cu addition. The stress corrosion cracking (SCC) behavior of three kinds of Ni-advanced weathering steel and a common weathering steel are examined in a simulated harsh marine environment by X-ray diffraction, scanning electron microscopy, electron backscattered diffraction, transmission electron microscopy, electrochemical tests, and slow strain rate tensile tests under different applied potentials. The results show that the SCC susceptibility of all test steel is low at open circuit potential. However, the SCC sensitivity of the conventional weathering steel increases significantly at − 1200 mV, while the Ni-advanced weathering steel exhibits good resistance to hydrogen embrittlement, which is attributed to the improved stacking fault energy, decrease of martensite-austenite constituents and refined grain size caused by increase in Ni and Mn content. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The effects of hydrogen charging on the electrochemical and stress corrosion cracking (SCC) behavior of X70 steel in a simulated deep seawater environment were investigated by using electrochemical measurements, slow strain rate tensile (SSRT) tests, and corrosion morphology characterization through SEM. The results showed that the concentrations of the adsorbed hydrogen in X70 steel after precharging under different hydrostatic pressures increased gradually and tended to be steady with the charging time. High hydrostatic pressures promoted the hydrogen permeation of X70 pipeline steel by promoting the permeating rate and quantity. The SCC susceptibility of X70 steel decreased first and then increased with the hydrogen-charging current density. The area reduction loss (Iψ) and true strain loss (Iε) exhibited the lowest SCC susceptibility at the 25 mA/cm2 hydrogen-precharging current density. The elongation rate loss (Iδ) exhibited the lowest SCC susceptibility at the 50 mA/cm2 hydrogen-precharging current density. [ABSTRACT FROM AUTHOR]

• Type 304 stainless steel is susceptible to SCC in liquid sulfur recovery unit. • Pitting, intergranular corrosion and corrosion thinning enhance the SCC. • Sulfuric acid and chloride ions can introduce fracture failure of 304 SS. Failure of a 304 stainless steel (304 SS) tube used as a steam heater in a liquid sulfur recovery unit was investigated by using various characterizing techniques. The investigation revealed the outer wall of the heat exchanger underwent severe pitting corrosion, and the formation of cracks was initiated from the outer wall pits. The cracks were branched and propagated mainly in a transgranular mode. Pitting, intergranular corrosion and corrosion thinning due to the external medium led to the failure of the heat exchanger by SCC. EDX and XRD analyses showed that the corrosive medium mainly contains sulfur compounds and some chloride ions. The findings in this study suggest that the failure of the 304 SS tube occurred due to pitting, intergranular corrosion and SCC caused by sulfuric acid and chloride ions. [ABSTRACT FROM AUTHOR]

In this work, a non-steady electrochemical model for assessing stress corrosion cracking (SCC) of 2205 duplex stainless steel (DSS) under applied polarization potentials was proposed, and the SCC mechanism was revealed. With the negative shift of potentials, hydrogen enhances SCC susceptibility by deteriorating passive film, inhibiting repassivation and causing serious damage. In particular, at −850 mV (vs. SCE), the synergetic effect of anodic dissolution (AD) and hydrogen embrittlement (HE) causes severe pitting and SCC. The negative shift of applied potentials changes the preferential pit/SCC initiation site due to high hydrogen concentration in austenite. • A non-steady electrochemical model for assessing SCC of 2205 duplex stainless steel was proposed. • The direct evidence was provided that the synergy of anodic dissolution and hydrogen embrittlement controls SCC. • The negative shift of potentials varies the initiation sites of pits and SCC because of hydrogen enrichment in austenite. [ABSTRACT FROM AUTHOR]

[Display omitted] • Branching cracks reveal the failure was attributed to stress corrosion cracking. • Initiation of SCC cracks mainly results from intergranular corrosion. • The SCC cracks propagated in a mixed mode of TGSCC and IGSCC. • Sensitized material, chloride and residual stress lead to the SCC failure synthetically. The investigation of this paper aimed at finding the failure cause of a heavily cracked geothermal water convection tube, utilizing electron backscattered diffraction, double loop potentiodynamic polarization test, and energy-dispersive X-ray spectroscopy. Results show the failure was attributed to stress corrosion cracking (SCC). Chloride in the service environment has induced the initiation of SCC cracks. The sensitization of matrix increased the susceptibility to intergranular cracking, which may result from improper heat treatment before service. The residual stress arising from the manufacturing process promoted the failure process. The SCC cracks originated from the internal tube. In the early stage, the cracks propagated along austenite grain boundaries. Thereafter, they transformed into a coexisting mode of intergranular cracking and transgranular cracking. The failure was attributed to the synthetical effect of sensitization, chloride, and residual stress. [ABSTRACT FROM AUTHOR]