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  • 1. A. Hosseini, V.
    et al.
    Karlsson, L.
    Örnek, Cem
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. Swerea KIMAB AB.
    Reccagni, P.
    Wessman, S.
    Engelberg, D.
    Microstructure and functionality of a uniquely graded super duplex stainless steel designed by a novel arc heat treatment method2018In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 139, p. 390-400Article in journal (Refereed)
    Abstract [en]

    A novel arc heat treatment technique was applied to design a uniquely graded super duplex stainless steel (SDSS), by subjecting a single sample to a steady state temperature gradient for 10 h. A new experimental approach was used to map precipitation in microstructure, covering aging temperatures of up to 1430 °C. The microstructure was characterized and functionality was evaluated via hardness mapping. Nitrogen depletion adjacent to the fusion boundary depressed the upper temperature limit for austenite formation and influenced the phase balance above 980 °C. Austenite/ferrite boundaries deviating from Kurdjumov–Sachs orientation relationship (OR) were preferred locations for precipitation of σ at 630–1000 °C, χ at 560–1000 °C, Cr2N at 600–900 °C and R between 550 °C and 700 °C. Precipitate morphology changed with decreasing temperature; from blocky to coral-shaped for σ, from discrete blocky to elongated particles for χ, and from polygonal to disc-shaped for R. Thermodynamic calculations of phase equilibria largely agreed with observations above 750 °C when considering nitrogen loss. Formation of intermetallic phases and 475 °C-embrittlement resulted in increased hardness. A schematic diagram, correlating information about phase contents, morphologies and hardness, as a function of exposure temperature, is introduced for evaluation of functionality of microstructures.

  • 2.
    Anantha, Krishnan Hariramabadran
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Örnek, Cem
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Ejnermark, S.
    Medvedeva, A.
    Sjöström, J.
    Pan, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    In situ AFM study of localized corrosion processes of tempered AISI 420 martensitic stainless steel: Effect of secondary hardening2017In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 164, no 13, p. C810-C818Article in journal (Refereed)
    Abstract [en]

    The effect of secondary hardening of tempered AISI 420 martensitic stainless steel on the corrosion behavior in aqueous 0.01 M NaCl has been studied, in-situ, using atomic force microscopy (AFM) to monitor real-time localized corrosion processes. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy, and X-ray diffraction analyses confirmed the presence of undissolved and secondary carbides (Cr23C6, Cr7C3, Cr3C2, Cr3C, Cr2C, and CrC) as well as retained austenite, all finely dispersed in the tempered martensitic matrix. Electrochemical measurements, consisted of monitoring of the open-circuit potential vs. time and cyclic polarization in 0.01 M NaCl solution, were performed to evaluate the passivity and its breakdown, and it was seen that initiation sites for localized corrosion were predominantly peripheral sites of carbides. In-situ AFM measurements revealed that there was a sequence for localized corrosion in which the neighboring matrix next to secondary carbides dissolved first, followed by corrosive attack on regions adjacent to undissolved carbides. Tempering at 500◦C reduced the corrosion resistance and the ability to passivate in comparison to tempering at 250◦C.

  • 3.
    Anantha, Krishnan Hariramabadran
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Örnek, Cem
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Ejnermark, Sebastian
    Uddeholms AB, Res & Dev, SE-68385 Hagfors, Sweden..
    Thuvander, Anders
    Uddeholms AB, Res & Dev, SE-68385 Hagfors, Sweden..
    Medvedeva, Anna
    Uddeholms AB, Res & Dev, SE-68385 Hagfors, Sweden..
    Sjostrom, Johnny
    Uddeholms AB, Res & Dev, SE-68385 Hagfors, Sweden..
    Pan, Jinshan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Experimental and modelling study of the effect of tempering on the susceptibility to environment-assisted cracking of AISI 420 martensitic stainless steel2019In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 148, p. 83-93Article in journal (Refereed)
    Abstract [en]

    The resistance to environment-assisted cracking (EAC) of AISI 420 martensitic stainless steel (MSS) was investigated in 0.3 M NaCl solution (room temperature) at constant loads for 30 days. The steel tempered at 250 degrees C was superior to the 500 degrees C-temper, which showed corrosion pits favouring cracking. The fracture surface showed faceted grains, cleavage, striations, and inter- and transgranular cracks, suggesting a mixed stress corrosion cracking (SCC) and hydrogen embrittlement (HE) mechanism as the cause for EAC. Finite element modelling (FEM) indicated strain/stress localization at the mouth of deep pits and at the wall of shallow pits, displaying the favoured locations for pit-to-crack transition.

  • 4.
    Kharitonov, Dmitry S.
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Sommertune, Jens
    RISE Res Inst Sweden, Surface Proc & Formulat, SE-11486 Stockholm, Sweden..
    Örnek, Cem
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Ryl, Jacek
    Gdansk Univ Technol, Dept Electrochem Corros & Mat Engn, 11-12 Narutowicza St, PL-80233 Gdansk, Poland..
    Kurilo, Irina I.
    Belarusian State Technol Univ, Organ Subst Technol Fac, Dept Phys Colloid & Analyt Chem, Minsk 220006, BELARUS..
    Claesson, Per M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Pan, Jinshan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Corrosion inhibition of aluminium alloy AA6063-T5 by vanadates: Local surface chemical events elucidated by confocal Raman micro-spectroscopy2019In: CORROSION SCIENCE, Vol. 148, p. 237-250Article in journal (Refereed)
    Abstract [en]

    Chemical interactions between aqueous vanadium species and aluminium alloy AA6063-T5 were investigated in vanadate-containing NaCl solutions. Confocal Raman and X-ray photoelectron spectroscopy experiments were utilised to gain insight into the mechanism of corrosion inhibition by vanadates. A greenish-grey coloured surface layer, consisting of V+4 and V+5 polymerized species, was seen to form on the alloy surface, especially on top of cathodic micrometre-sized IMPs, whereby suppressing oxygen reduction kinetics. The results suggest a two-step mechanism of corrosion inhibition in which V+5 species are first reduced to V+4 or V+3 species above cathodic IMPs, and then oxidized to mixed-valence V+5/V+4 polymerized compounds.

  • 5.
    Kharitonov, Dmitry S.
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. Belarusian State Technol Univ, Chem Technol & Engn Fac, Dept Chem Electrochem Prod Technol & Mat Elect Eq, Minsk 220006, BELARUS..
    Örnek, Cem
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. Swerea KIMAB, Dept Corros Energy & Proc Ind, SE-16440 Kista, Sweden..
    Claesson, Per M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Sommertune, Jens
    RISE Res Inst Sweden, Chem Mat & Surfaces, SE-11486 Stockholm, Sweden..
    Zharskii, Ivan M.
    Belarusian State Technol Univ, Chem Technol & Engn Fac, Dept Chem Electrochem Prod Technol & Mat Elect Eq, Minsk 220006, BELARUS..
    Kurilo, Irina I.
    Belarusian State Technol Univ, Organ Subst Technol Fac, Dept Phys Colloid & Analyt Chem, Minsk 220006, BELARUS..
    Pan, Jinshan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Corrosion Inhibition of Aluminum Alloy AA6063-T5 by Vanadates: Microstructure Characterization and Corrosion Analysis2018In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 165, no 3, p. C116-C126Article in journal (Refereed)
    Abstract [en]

    Corrosion inhibition of aluminum alloy AA6063-T5 by vanadates (NaVO3) in 0.05 M NaCl solution has been investigated by electrochemical and weight loss measurements, and associated with microstructure and Volta potential data. X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy analyses confirmed the presence of micrometer-sized Fe-rich Al4.01MnSi0.74, Al1.69Mg4Zn2.31, and FeAl3 intermetallic phases (IMPs) and nanometer-sized CuAl2, ZnAl2, and Mg2Si precipitates in the microstructure. Scanning Kelvin probe force microscopy measurements showed Volta potential differences of up to 600 mV between the microstructure constituents indicating a high susceptibility to micro-galvanic corrosion, with interphase boundary regions exhibiting the highest propensity to corrosion. Most IMPs had cathodic character whereas some nanometer-sized Mg-rich particles exhibited anodic nature, with large Volta potential gradients within interphase regions of large cathodic particles. Electrochemical potentiodynamic polarization measurements indicated that the vanadates provided mixed corrosion inhibition effects, mitigating both oxygen reduction, occurring on cathodic IMPs, and anodic metal dissolution reaction, occurring on anodic sites, such as Mg2Si and interphase boundary regions. Electrochemical measurements indicated that the sodium metavanadate inhibitor blocks active metal dissolution, giving high inhibition efficiency (>95%) during the initial exposure, whereas long-term weight loss measurements showed that the efficacy decreases after prolonged exposure.

  • 6.
    Långberg, Marie
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. SWERIM, SE-16407 Kista, Sweden..
    Örnek, Cem
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Zhang, Fan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Coating Technology.
    Cheng, J.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Coating Technology.
    Liu, M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Coating Technology.
    Granaes, E.
    Deutsch Elektronen Synchrotron DESY, D-22607 Hamburg, Germany..
    Wiemann, C.
    Res Ctr Julich, Peter Grunberg Inst PGI 6, D-52425 Julich, Germany..
    Gloskovskii, A.
    Deutsch Elektronen Synchrotron DESY, D-22607 Hamburg, Germany..
    Matveyev, Y.
    Deutsch Elektronen Synchrotron DESY, D-22607 Hamburg, Germany..
    Kulkarni, S.
    Deutsch Elektronen Synchrotron DESY, D-22607 Hamburg, Germany..
    Noei, H.
    Deutsch Elektronen Synchrotron DESY, D-22607 Hamburg, Germany..
    Keller, T. F.
    Deutsch Elektronen Synchrotron DESY, D-22607 Hamburg, Germany.;Univ Hamburg, Phys Dept, D-20355 Hamburg, Germany..
    Lindell, D.
    SWERIM, SE-16407 Kista, Sweden..
    Kivisakk, U.
    AB Sandvik Mat Technol, SE-81181 Sandviken, Sweden..
    Lundgren, E.
    Lund Univ, Div Synchrotron Radiat Res, SE-22100 Lund, Sweden..
    Stierle, A.
    Deutsch Elektronen Synchrotron DESY, D-22607 Hamburg, Germany.;Univ Hamburg, Phys Dept, D-20355 Hamburg, Germany..
    Pan, Jinshan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Characterization of Native Oxide and Passive Film on Austenite/Ferrite Phases of Duplex Stainless Steel Using Synchrotron HAXPEEM2019In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 166, no 11, p. C3336-C3340Article in journal (Refereed)
    Abstract [en]

    A new measurement protocol was used for microscopic chemical analysis of surface oxide films with lateral resolution of 1 mu m. The native air-formed oxide and an anodic passive film on austenite and ferrite phases of a 25Cr-7Ni super duplex stainless steel were investigated using synchrotron hard X-ray photoemission electron microscopy (HAXPEEM). Pre-deposited Pt-markers, in combination with electron backscattering diffraction mapping (EBSD), allowed analysis of the native oxide on individual grains of the two phases and the passive film formed on the same area after electrochemical polarization of the sample. The results showed a certain difference in the composition of the surface films between the two phases. For the grains with (001) crystallographic face // sample surface, the native oxide film on the ferrite contained more Cr oxide than the austenite. Anodic polarization up to 1000 mV/(Ag/AgCl) in 1M NaCl solution at room temperature resulted in a growth of the Cr- and Fe-oxides, diminish of Cr-hydroxide, and an increased proportion of Fe3+ species. by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited.

  • 7.
    Örnek, Cem
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Additive manufacturing–a general corrosion perspective2018In: Corrosion Engineering, Science and Technology, ISSN 1478-422X, E-ISSN 1743-2782, Vol. 53, no 7, p. 531-535Article in journal (Refereed)
    Abstract [en]

    Metallic additive manufacturing will replace some materials produced by conventional fabrication methods in the nearest future. However, corrosion will remain an important aspect needed to be prevented. The corrosion behaviour of additively manufactured alloys has been sparsely studied and very little work has been published so far. In this article, a general discussion about materials produced by additive manufacturing will be provided. 

  • 8.
    Örnek, Cem
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Engelberg, D. L.
    Univ Manchester, Corros & Protect Ctr, Sackville St, Manchester M13 9PL, Lancs, England.;Univ Manchester, Mat Performance Ctr, Sch Mat, Sackville St, Manchester M13 9PL, Lancs, England..
    Toward Understanding the Effects of Strain and Chloride Deposition Density on Atmospheric Chloride-Induced Stress Corrosion Cracking of Type 304 Austenitic Stainless Steel Under MgCl2 and FeCl3:MgCl2 Droplets2019In: Corrosion, ISSN 0010-9312, E-ISSN 1938-159X, Vol. 75, no 2, p. 167-182Article in journal (Refereed)
    Abstract [en]

    Type 304 (UNS S30400) austenitic stainless steel was exposed for 6 months under elastic (0.1%) and elastic/plastic (0.2%) strain to MgCl2 and mixed MgCl2:FeCl3 droplets with varying chloride deposition densities (1.5 mu g/cm(2)-1,500 mu g/cm(2)) at 30% relative humidity (RH) and 50 degrees C. The occurrence of pitting corrosion, crevice corrosion, atmospheric chloride-induced stress corrosion cracking (AISCC), and hydrogen embrittlement (HE) was observed, and the average crack growth rates estimated. Exposure to elastic/plastic strain resulted in longer and more severe cracks. AISCC was found at chloride deposition densities down to 14.5 mu g/cm(2), whereas no cracks were seen at lower deposition densities, with cracks developing at pit or crevice corrosion sites. More severe cracks were seen under MgCl2 droplets as contrasted to mixed MgCl2:FeCl3 salt droplets, which were seen to promote more localized corrosion sites with deeper penetration and in conjunction with shorter crack lengths. Differences in AISCC propagation rates and associated crack morphologies are discussed in relation to understanding long-term atmospheric corrosion exposures.

  • 9.
    Örnek, Cem
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Leygraf, Christofer
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Pan, Jinshan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    On the Volta potential measured by SKPFM - fundamental and practical pects with relevance to corrosion science2019In: Corrosion Engineering, Science and Technology, ISSN 1478-422X, E-ISSN 1743-2782, Vol. 54, no 3, p. 185-198Article, review/survey (Refereed)
    Abstract [en]

    The Volta potential is an electron-sensitive parameter and describes the ermodynamic propensity of a metal to take part in electrochemical actions. It has found widespread acceptance among corrosion searchers due to its connection to the corrosion potential and its sy measurability in local scale, being often used to study localised rrosion phenomena and micro-galvanic activities. The principle object this paper is to provide a comprehensive, fundamental insight into e meaning of the Volta potential and to define a polarity convention measured potentials by the scanning Kelvin probe force microscopy KPFM) in order to assess local nobilities in microstructures. nditions to relate the Volta potential with the mixed-potential theory e discussed and a possible connection to corrosion phenomena plained. The limitations of the Volta potential as well as the SKPFM chnique are also aimed to be explained, with some practical formation to maximise the output of high quality data.

  • 10.
    Örnek, Cem
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Leygraf, Christopher
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Pan, Jinshan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Passive film characterisation of duplex stainless steel using scanning Kelvin probe force microscopy in combination with electrochemical measurements2019In: npJ Materials Degradation, ISSN 2397-2106, Vol. 3, no 1, p. 1-8Article in journal (Refereed)
    Abstract [en]

    The characterisation of passive oxide films on heterogeneous microstructures is needed to assess local degradation (corrosion, cracking) in aggressive environments. The Volta potential is a surface-sensitive parameter which can be used to assess the surface nobility and hence passive films. In this work, it is shown that the Volta potential, measured on super duplex stainless steel by scanning Kelvin probe force microscopy, correlates with the electrochemical properties of the passive film, measured by electrochemical impedance spectroscopy and potentiodynamic polarisation. Natural oxidation by ageing in ambient air as well as artificial oxidation by immersion in concentrated nitric acid improved the nobility, both reflected by increased Volta potentials and electrochemical parameters. Passivation was associated with vanishing of the inherent Volta potential difference between the ferrite and austenite, thereby reducing the galvanic coupling and hence improving the corrosion resistance of the material. Hydrogen-passive film interactions, triggered by cathodic polarisation, however, largely increased the Volta potential difference between the phases, resulting in loss of electrochemical nobility, with the ferrite being more affected than the austenite. A correlative approach of using the Volta potential in conjunction with electrochemical data has been introduced to characterise the nobility of passive films in global and local scale.

  • 11.
    Örnek, Cem
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. Swerea KIMAB AB, Isafjordsgatan 28A, Kista, 164 40, Sweden.
    Liu, Min
    Univ Sci & Technol Beijing, Natl Ctr Mat Serv Safety, Xueyuan Rd 30, Beijing 100083, Peoples R China..
    Pan, Ying
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Jin, Y.
    Univ Sci & Technol Beijing, Natl Ctr Mat Serv Safety, Xueyuan Rd 30, Beijing 100083, Peoples R China..
    Leygraf, Christopher
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Volta Potential Evolution of Intermetallics in Aluminum Alloy Microstructure Under Thin Aqueous Adlayers: A combined DFT and Experimental Study2018In: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 61, no 9-11, p. 1169-1182Article in journal (Refereed)
    Abstract [en]

    In this work, first-principle density functional theory (DFT) was used to calculate the work function and Volta potential differences between aluminum alloy matrix and two intermetallic phases (Mg2Si and Al2Cu) with varying surface terminations as a function of adhering monolayers (ML) of water. The calculated data were compared with experimental local Volta potential data obtained by the scanning Kelvin probe force microscopy (SKPFM) on a commercial aluminum alloy AA6063-T5 in atmospheric environments with varying relative humidity (RH). The calculations suggest that the surface termination has a major effect on the magnitude and polarity of the Volta potential of both intermetallic phases (IMP's). The Volta potential difference between the IMP's and the aluminum matrix decreases when the surface is gradually covered by water molecules, and may further change as a function of adhering ML's of water. This can lead to nobility inversions of the IMP's relative to the aluminum matrix. The measured Volta potential difference between both IMP's and their neighboring matrix is dependent on RH. Natural oxidation in ambient indoor air for 2 months led to a nobility inversion of the IMP's with respect to the aluminum matrix, with the intermetallics showing anodic nature already in dry condition. The anodic nature of Al2Cu remained with the introduction of RH, whereas Mg2Si became cathodic at high RH, presumably due to de-alloying of Mg and oxide dissolution. The DFT calculations predicted an anodic character of both IMP's in reference to the oxidized aluminum matrix, being in good agreement with the SKPFM data. The DFT and SKPFM data were discussed in light of understanding localized corrosion of aluminum alloys under conditions akin to atmospheric exposure.

  • 12.
    Örnek, Cem
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Långberg, Marie
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Evertsson, Jonas
    Lund Univ, Div Synchrotron Radiat Res, SE-22100 Lund, Sweden..
    Harlow, Gary
    Lund Univ, Div Synchrotron Radiat Res, SE-22100 Lund, Sweden..
    Linpe, Weronica
    Lund Univ, Div Synchrotron Radiat Res, SE-22100 Lund, Sweden..
    Rullik, Lisa
    Lund Univ, Div Synchrotron Radiat Res, SE-22100 Lund, Sweden..
    Carla, Francesco
    European Synchrotron Radiat Facil, F-38000 Grenoble, France..
    Felici, Roberto
    Area Ric Roma 2 Tor Vergata, SPINCNR, I-00133 Rome, Italy..
    Bettini, Eleonora
    Sandvik Mat Technol, SE-81181 Sandviken, Sweden..
    Kivisakk, Ulf
    Sandvik Mat Technol, SE-81181 Sandviken, Sweden..
    Lundgren, Edvin
    Lund Univ, Div Synchrotron Radiat Res, SE-22100 Lund, Sweden..
    Pan, Jinshan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    In-situ synchrotron GIXRD study of passive film evolution on duplex stainless steel in corrosive environment2018In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 141, p. 18-21Article in journal (Refereed)
    Abstract [en]

    This paper presents new findings about the passive film formed on super duplex stainless steel in ambient air and corrosive environments, studied by synchrotron grazing-incidence X-ray diffraction (GIXRD). The passive film, formed in air, was seen to be a nano-crystalline mixed-oxide. Electrochemical polarisation to the passive region in aqueous 1 M NaCl at room temperature resulted in an increase of the passive film thickness, preferential dissolution of Fe, and partial loss of crystallinity. After termination of polarization to the transpassive regime, reformation of the mixed-oxides was observed, showing a thicker, semi-crystalline, and more defective nature (more vacancies) with further new oxides/hydroxides.

  • 13.
    Örnek, Cem
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Långberg, Marie
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. Swerim, SE-16407 Kista, Sweden..
    Evertsson, Jonas
    Lund Univ, Div Synchrotron Radiat Res, SE-22100 Lund, Sweden.;Deutsch Elektronen Synchrotron DESY, D-22607 Hamburg, Germany.;Justus Liebig Univ Giessen, Phys Chem Dept, D-35392 Giessen, Germany..
    Harlow, Gary
    Lund Univ, Div Synchrotron Radiat Res, SE-22100 Lund, Sweden..
    Linpe, Weronica
    Lund Univ, Div Synchrotron Radiat Res, SE-22100 Lund, Sweden..
    Rullik, Lisa
    Lund Univ, Div Synchrotron Radiat Res, SE-22100 Lund, Sweden..
    Carla, Francesco
    Diamond Light Source, Didcot OX11 0DE, Oxon, England..
    Felici, Roberto
    SPINCNR, Area Ric Roma 2 Tor Vergata, I-00133 Rome, Italy..
    Kivisakk, Ulf
    Sandvik Mat Technol, SE-81181 Sandviken, Sweden..
    Lundgren, Edvin
    Lund Univ, Div Synchrotron Radiat Res, SE-22100 Lund, Sweden..
    Pan, Jinshan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Influence of Surface Strain on Passive Film Formation of Duplex Stainless Steel and Its Degradation in Corrosive Environment2019In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 166, no 11, p. C3071-C3080Article in journal (Refereed)
    Abstract [en]

    The effect of surface strain on the passive film evolution of SAF 2507 super duplex stainless steel exposed to ambient air and 0.1 M NaCl solution with varying anodic polarization at room temperature has been investigated using in-situ grazing incidence X-ray diffraction (GIXRD) in combination with electrochemical measurements. Surface strain affected the crystallinity of the passive film as such that the surface oxides/hydroxides were predominantly amorphous, with some minor crystalline CrOOH and FeOOH present in the film. Crystalline CrOOH was seen to diminish in volume upon immersion in the NaCl solution, well-possibly becoming amorphous during anodic polarization, whereas crystalline FeOOH was seen to increase in volume during polarization to the passive potential regime. Strain relaxation, associated with metal dissolution, occurred in both austenitic and ferritic grains during immersion in the electrolyte. Anodic polarization to the transpassive regime led to maximum strain relaxation, occurring more on the austenite than the ferrite. The selective transpassive dissolution nature of the ferrite was significantly reduced due to large strains in the austenite. Passive film breakdown was reflected by enhanced dissolution of Fe, Cr, Mo and Ni occurring simultaneously around 1300 mV vs. Ag/AgCl. 

  • 14.
    Örnek, Cem
    et al.
    KTH.
    Reccagni, Pierfranco
    Kivisakk, Ulf
    Bettini, Eleonora
    Engelberg, Dirk L.
    Pan, Jinshan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Hydrogen embrittlement of super duplex stainless steel - Towards understanding the effects of microstructure and strain2018In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 43, no 27, p. 12543-12555Article in journal (Refereed)
    Abstract [en]

    The effects of austenite spacing, hydrogen charging, and applied tensile strain on the local Volta potential evolution and micro-deformation behaviour of grade 2507 (UNS 532750) super duplex stainless steel were studied. A novel in-situ methodological approach using Digital Image Correlation (DIC) and Scanning Kelvin Probe Force Microscopy (SKPFM) was employed. The microstructure with small austenite spacing showed load partitioning of tensile micro-strains to the austenite during elastic loading, with the ferrite then taking up most tensile strain at large plastic deformation. The opposite trend was seen when the microstructure was pre-charged with hydrogen, with more intense strain localisation formed due to local hydrogen hardening. The hydrogen-charged microstructure with large austenite spacing showed a contrasting micro-mechanical response, resulting in heterogeneous strain localisation with high strain intensities in both phases in the elastic regime. The austenite was hydrogen-hardened, whereas the ferrite became more strain-hardened. SKPFM measured Volta potentials revealed the development of local cathodic sites in the ferrite associated with hydrogen damage (blister), with anodic sites related to trapped hydrogen and/or micro voids in the microstructure with small austenite spacing. Discrete cathodic sites with large Volta potential variations across the ferrite were seen in the coarse-grained microstructure, indicating enhanced susceptibility to micro-galvanic activity. Microstructures with large austenite spacing were more susceptible to hydrogen embrittlement, related to the development of tensile strains in the ferrite.

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