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Hanmin Zhang - One of the best experts on this subject based on the ideXlab platform.

Torbjorn Jonsson - One of the best experts on this subject based on the ideXlab platform.

  • The Influence of Oxide-Scale Microstructure on KCl(s)-Induced Corrosion of Low-Alloyed Steel at 400 °C
    Oxidation of Metals, 2019
    Co-Authors: Mercedes Andrea Olivas-ogaz, Jesper Liske, Johan Eklund, Amanda Persdotter, Mohammad Sattari, Jan-erik Svensson, Torbjorn Jonsson
    Abstract:

    The high-temperature corrosion of low-Alloyed Steels and stainless Steels in the presence of KCl(s) has been studied extensively in the last decades by several authors. The effect of KCl(s) on the initial corrosion attack has retained extra focus. However, the mechanisms behind the long-term behavior, e.g., when an oxide scale has already formed, in the presence of KCl(s) are still unclear. The aim of this study was to investigate the effect of the microstructure of a pre-formed oxide scale on low-Alloyed Steel (Fe–2.25Cr–1Mo) when exposed to small amounts of KCl(s). The pre-oxidation exposures were performed at different temperatures and durations in order to create oxide scales with different microstructures but with similar thicknesses. After detailed characterization, the pre-oxidized samples were exposed to 5%O_2 + 20%H_2O + 75%N_2 (+KCl(s)) at 400 °C for 24, 48, and 168 h and analyzed with scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and focused ion beam. The microstructural investigation indicated that Cl-induced corrosion is a combination of oxide thickness and microstructure, and the breakaway mechanism in the presence of KCl(s) is diffusion-controlled as porosity changes prior to breakaway oxidation were observed.

  • initial corrosion attack of 304l and t22 in 2 mw biomass gasifier a microstructural investigation
    Materials at High Temperatures, 2015
    Co-Authors: Hamed Hoseini Hooshyar, Jesper Liske, Larsgunnar Johansson, Martin Seemann, Torbjorn Jonsson
    Abstract:

    The work investigates the initial corrosion attack on a low Alloyed Steel and a stainless Steel in a 2 MW test gasifier. The gasifier environment generates homogenous deposits that consist mainly of carbon containing species, potassium sulphate, potassium chloride and zinc sulphide. The stainless Steel exhibits better corrosion resistance compared to the low Alloyed Steel and the analysis indicates a protective thin scale covering parts of the surface after 4 h exposure. However, in some areas the oxide scale has lost its protective properties and thicker oxide scales are seen. The thick oxide islands consist of an inward growing Fe,Cr,Ni oxide and an outward growing iron oxide. The low Alloyed Steel shows a more homogenous and faster initial corrosion attack. The thick scales exhibit a sharp straight line in the middle of the scale that separates the bottom spinel oxide from the outer iron rich parts of the scale. It is considered that this flat interface corresponds to the original sample surface.

  • an esem in situ investigation of initial stages of the kcl induced high temperature corrosion of a fe 2 25cr 1mo Steel at 400 c
    Corrosion Science, 2011
    Co-Authors: Torbjorn Jonsson, Larsgunnar Johansson, Jan-erik Svensson, Nicklas Folkeson, Mats Halvarsson
    Abstract:

    The initial oxidation of a low-Alloyed Steel (Fe-2.25Cr-1Mo) in the presence of small amounts of KCl(s) have been investigated through ESEM in situ exposure and analysis at 400 degrees C. The samples were also characterized by XRD, SEM/EDX and FIB. The present study shows the corrosive nature of KCl towards the low Alloyed Steel. It is concluded that the initial KCl distribution is important and that a KCl/FeCl2 liquid phase film forms on large parts of the oxide surface in the presence of KCl. It is proposed that Cl increases the oxidation rate (by decorating oxide grain boundaries) and decreases the oxide scale adhesion. (C) 2011 Elsevier Ltd. All rights reserved.

Klaus Peters - One of the best experts on this subject based on the ideXlab platform.

  • use of pre oxidation to improve reactive wetting of high manganese Alloyed Steel during hot dip galvanizing
    Surface & Coatings Technology, 2011
    Co-Authors: Marc Blumenau, Martin Norden, Frederic Friedel, Klaus Peters
    Abstract:

    Abstract The present study discusses hot-dip galvanizing of a Fe–23% Mn–0.6% C–0.3% Si Steel using a Zn–0.22%Al bath. The paper concentrates on reactive Zn wetting on top a covering external oxide layer occurring after in-line annealing. Annealing was performed by soaking at 800 °C/60 s in 5% H 2 –N 2 at different dewpoints. In-line pre-oxidation at 600 °C/10 s in 1.8% O 2 –N 2 was further performed and the impact on selective oxidation as well as reactive Zn wetting was examined. After conventional annealing Zn wetting turns to increase if a roughly globular MnO layer appears on the external Steel surface and Si is internally oxidized. Reactive wetting including the formation of Fe 2 Al 5 crystals occurs on top of the MnO layer, because metallic-bond Fe exists incorporated within this MnO layer (→MnO·Fe metall layer). The amount of metallic-bond Fe within the MnO·Fe metall layer increases considerably if pre-oxidation is conducted. This results in an intensified Fe 2 Al 5 formation on top of a MnO·Fe metall , which improves liquid Zn wetting. Brittle Fe–Zn intermetallics were absent in all trials. These results offer a new way for hot-dip galvanizing (high) Mn Alloyed Steels. The absence of Fe–Zn intermetallics and (partial) MnO reduction implies that the currently discussed model of aluminothermic MnO reduction during hot-dip galvanizing Mn Alloyed Steel seems not to be dominating in the present case of reactive Zn wetting on top of a covering MnO·Fe metall layer.

  • reactive wetting during hot dip galvanizing of high manganese Alloyed Steel
    Surface & Coatings Technology, 2011
    Co-Authors: Marc Blumenau, Martin Norden, Frank Friedel, Klaus Peters
    Abstract:

    Abstract The present study discusses reactive wetting during hot-dip galvanizing of high Mn Alloyed Steel (X-IP1000, 23 wt.% Mn) and is focused on investigating the influence of the metallic Mn concentration in the Steel bulk composition on phase formation at the interface Steel/coating. Samples were in-line bright annealed (1100 °C/ 60 s in N2-5%H2 at DP −50 °C) prior hot-dipping to avoid external MnO on the Steel surface. This approach was applied to avoid influencing the wetting reaction by an aluminothermic MnO reduction, because this is considered to lead to an unwanted zeta-phase (FeZn13) formation in the coating by hot-dipping of Mn Alloyed Steels ( 2 Al 5 phase. This shows that the model of aluminothermic MnO reduction failed in the present case. This study suggests an alternative model explaining the appearance of zeta-phase with the removal of bath-Al by metallic Mn, which is dissolved out of the Steel bulk into the Zn bath. The present investigation shows that alloying elements in the Steel bulk may influence coating quality not only “indirectly” by external formation of nonwettable oxides, but also “directly” by influencing phase equilibria and kinetics of the wetting reaction. Understanding these phenomena will improve processing of (high) Alloyed Steel concepts as well as industrial Zn bath management.

Malek Naderi - One of the best experts on this subject based on the ideXlab platform.

  • The effect of strain rate and deformation temperature on the characteristics of isothermally hot compressed boron-Alloyed Steel
    Materials Science and Engineering: A, 2012
    Co-Authors: Mahmoud Abbasi, A. Saeed-akbari, Malek Naderi
    Abstract:

    Abstract In the current work, the effects of deformation temperature and strain rate on microstructure and mechanical properties of a boron-Alloyed Steel after being isothermally compressed and subsequently quenched are investigated. The results indicate that at a constant strain rate, the hardness and martensite start temperature (Ms) normally increase as the deformation temperature increases. It is also observed that higher strain rates increase the hardness and flow stress, although a clear effect of strain rate on Ms is not observed. It is concluded that while increase of deformation temperature reduces the work hardening rate, the effects of strain rate on work hardening rate is intricate. Additionally, some models to deal with the work hardening rate variations as a function of temperature and strain rate are represented. Finally, the changes of flow stress, Ms temperature, hardness, and martensite volume fraction are compared in terms of the applied process routes: isothermal deformation followed by cooling, and simultaneous deformation and cooling processes.

Rahul K Verma - One of the best experts on this subject based on the ideXlab platform.

  • tensile flow behavior of ultra low carbon low carbon and micro Alloyed Steel sheets for auto application under low to intermediate strain rate
    Materials & Design, 2014
    Co-Authors: Surajit Kumar Paul, Abhishek Raj, P Biswas, G Manikandan, Rahul K Verma
    Abstract:

    This paper is concerned with tensile characteristics of auto grade low carbon, ultra low carbon and micro Alloyed Steel sheets under low to intermediate strain rates ranging from 0.0007 to 250 s � 1 . Experimental investigation reveals two important aspects of these Steels under intermediate strain rate deformation. Firstly, the yield stress increases with strain rate in all these Steels. Of course yield stress increment is higher for low carbon and ultra low carbon Steel sheets. Secondly, the strain hardening rate drastically decreases with strain rate for low carbon and ultra low carbon Steel sheets, whereas it remains steady for micro Alloyed Steel sheets. Based on these observations, a constitutive model has been proposed which predicts the strain rate sensitive flow behavior of all these grades within the strain rate range of automotive crash event.