Evaluation of the “nickel effect” in sulfide stress cracking of low alloy steels using thiosulfate as an alternative to H2S-containing environments

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Evaluation of tungsten as a hydrogen permeation barrier in reduced activation steel F82H for nuclear fusion applications

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The Role of Nickel in Low Alloy Steels exposed to H2S-containing environments. Part I: Trench Formation at the Open Circuit Potential

The nickel content in low alloy steels (LAS) for oil and gas exploration and production is limited to a maximum of 1 wt.% according to ANSI/NACE MR 0175/ISO 15156. This restriction is imposed to avoid sulfide stress cracking (SSC) in sour (H2S-containing) environments. In this work, the effect of Ni on SSC of LAS was studied independently of other alloying elements. For this purpose, quenched and tempered steels heat treated to a yield strength of 610 MPa with a Ni content below and above the 1 wt.% threshold were evaluated at the open circuit potential (OCP) in unstressed specimens, and in slow strain rate tests (SSRT) at room temperature. Thiosulfate was used as a surrogate of H2S, according to the Tsujikawa method. It is concluded that Ni contributes to the stabilization of the sulfide films that form on the steel´s surface at OCP. The rupture of this film due to tensile stress promotes the nucleation of elongated deep pits, referred to as trenches, which can act as sulfide stress crack initiators. Trenches were observed exclusively in stressed, Ni-containing specimens. Moreover, trenches´ morphology, dimensions, and distribution varied with the Ni content in the steels. For the steels studied in this work, the Ni effect on trenching persisted below the 1 wt.% threshold.Fil: Chalfoun, Dannisa Romina. Universidad Nacional de San Martín. Instituto Sabato; Argentina. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Kappes, Mariano Alberto. Universidad Nacional de San Martín. Instituto Sabato; Argentina. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Perez, Teresa E.. Universidad Nacional de San Martín. Instituto Sabato; ArgentinaFil: Otegui, José L.. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Iannuzzi, Mariano. Curtin University; Australi

Hydrogen solubility, diffusivity, and trapping in quenched and tempered Ni-containing steels

Hydrogen permeation experiments were performed in quenched and tempered (Q&T) low alloy steels with varying Ni contents exposed to 1 bar H2 at 30, 50 and 70 °C. From the analysis of build-up and decay transients, it is concluded that the permeation coefficient, the apparent diffusion coefficient (Dapp) and the concentration of hydrogen in interstitial sites on the charging surface (C0) decreases as the Ni concentration increases from 0 to 5 wt.%. The total concentration of hydrogen on the charging surface (C0,r), which includes interstitial and reversibly trapped hydrogen, is about an order of magnitude larger than C0. The hydrogen binding energy (Eb) and trap density (Nr) were calculated from the Dapp vs. temperature dependence, under the hypothesis of low trap occupancy. C0,r, Eb and Nr do not show a clear correlation with Ni content, indicating that trapping is controlled by a microstructural feature other than Ni atoms in solid solution.Fil: Chalfoun, Dannisa Romina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martín. Instituto Sabato; Argentina. YPF - Tecnología; ArgentinaFil: Kappes, Mariano Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martín. Instituto Sabato; Argentina. Comisión Nacional de Energía Atómica; ArgentinaFil: Bruzzoni, Pablo. Comisión Nacional de Energía Atómica; ArgentinaFil: Iannuzzi, Mariano. Curtin University; Australi