M. Spiegel

Max Planck Institute for Iron Research GmbH, Düsseldorf, North Rhine-Westphalia, Germany

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Publications (50)45.66 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The dependence of surface segregation of P and S, on temperature and dew point of the annealing atmosphere was studied for an Fe–1Mn–0.02P–0.008S (all in wt.%) model alloy. The specimens were annealed for 1min within a temperature window of 400 to 800°C, in N2–5%H2 gas atmospheres with a wide range of dew points −80 to 0°C. Surface analyses were carried out by using XPS and FE-SEM. At the dew points −80 and −40°C segregation of P was observed at 400 and 600°C but S segregation occurred only at 800°C. Phosphorus accumulation increases significantly with increase of dew point and, moreover, at the higher dew point, P replaces S at 800°C.
    Surface & Coatings Technology - SURF COAT TECH. 01/2011; 205(16):4089-4093.
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    ABSTRACT: Thin metallic coatings (0.3 and ) were deposited by magnetron cosputtering on bare and on 100 h preoxidized ZMG232L stainless steel substrates for application as protective coatings for solid oxide fuel cells (SOFCs) interconnects. The coatings on bare steel were oxidized for different times of up to 101 h at in ambient air. After 1 h heat-treatment, the metallic films had already converted to oxide with a spinel structure. With increasing oxidation time, a phase was also detected, independent of the thickness of the coatings. This phase formation was attributed to Mn ion enrichment in the coating. Cr diffusion and stresses in the thin coatings were also observed. Bare steel samples were also preoxidized for different durations to determine a suitable oxidation time to form a stable oxide scale on their surface. Steel samples preoxidized for 100 h and coated with were subjected to time-dependent area specific resistance (ASR) measurements for 500 h. The ASR values obtained were 15 and for the substrate coated with 0.3 and , respectively. Also, no phase was present, and no Cr diffusion was detected in the thicker coating.
    Journal of The Electrochemical Society. 11/2009; 156(12):B1431-B1439.
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    ABSTRACT: The current investigation aims in understanding the effect of short-term (300s) annealing of NiTi shape memory alloys (SMAs) in a reducing atmosphere of N2–10% H2. The influence of temperature on the resulting surface morphology and chemistry is elucidated. On annealing at 600°C, the surface is covered with a thin layer of titanium oxide, which is 7.5nm thick, while at 800°C, the surface is covered with a golden-yellow layer of TiN of thickness more than 100nm. The surface analysis carried out by XPS on the specimen annealed at 800°C confirms the formation of TiN and more notably, the surface is devoid of Ni.
    CoRR. Sci., v.51, 635-641 (2009). 01/2009;
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    ABSTRACT: Thin metallic Mn–Co films (0.3μm thickness) were produced by RF-magnetron co-sputtering on SiO2/Si and on ZMG232L steel substrates. The deposition was followed by a heat treatment in order to convert the metallic coatings to (Mn,Co)3O4 spinel oxides. All steel samples were analyzed after 1h heat treatment in order to confirm the presence of the spinel structure on top of the steel, as well as to investigate and characterise the evolution and growth of oxides, namely (Mn,Cr)3O4 and Cr2O3, at the internal steel/coating interface. From the structural and morphological characterization, the presence of a well-adherent approximately 0.5μm thick Mn1.5Co1.5O4 coating was confirmed. After this preparatory annealing, selected samples were heat-treated in simulated cathodic or anodic atmospheres at 800°C for 500h in order to investigate the properties of the coatings after long time annealing. For the samples annealed in cathodic-like atmospheres, Cr was present on the surface of the coating, whereas for the samples annealed in anodic-like atmospheres, MnO was the main phase observed on the surface. Measurements of the area specific resistance performed on the steel coated with Mn50Co50 showed a resistivity of around 59mΩcm after 601h annealing in ambient air.
    Applied Surface Science 12/2008; 255(5):1850. · 2.54 Impact Factor
  • Proceedings of the 8th European SOFC Forum, Lucerne, Switzerland; 06/2008
  • TMS 2008 Annual Meeting Supplemental Proceedings, New Orleans, USA; 03/2008
  • Srinivasan Swaminathan, Michael Spiegel
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    ABSTRACT: In order to understand the effect of Si and Mn concentration on the selective oxidation of Cr, the model alloys of Fe–1% Si–0.8% Cr, Fe–2% Si–0.8% Cr, Fe–1% Mn–0.8% Cr and Fe–2% Mn–0.8% Cr (all in wt%) were studied. The specimens were annealed at 820 °C in N2–5%H2 gas atmospheres with the different dew points (DPs) of − 80, − 40 and − 29 °C, respectively. Surface analyses were carried out by using the XPS and field emission (FE)-SEM. Only binary oxides of the alloying elements were observed on the surface of all the ternary model alloys annealed at a low DP of − 80 °C. Increasing the DP to − 40 °C leads to maximum external oxidation of the alloying elements. In the Fe–1% Si–0.8% Cr alloy, annealing at the higher DP of − 29 °C promotes internal oxidation of Cr. On the other hand, increasing the Si concentration in the FeCr alloy (i.e. Fe–2% Si–0.8% Cr), the maximum external oxidation of Cr was observed due to the decrease of surface oxygen potential by Si. Moreover, the oxidation kinetics seems to play a decisive role, i.e. the oxygen competition between Si and Cr leads to partial oxidation of these elements. In both FeMnCr alloys, the effect of Mn concentration on the selective oxidation of Cr is indistinguishable, however, apart from their binary oxides (MnO/Mn3O4, Cr2O3), the MnCr chemical interaction causes the formation of ternary oxide (MnCr2O4) at the DP of − 40 and − 29 °C. Copyright © 2008 John Wiley & Sons, Ltd.
    Surface and Interface Analysis 02/2008; 40(3‐4):268 - 272. · 1.22 Impact Factor
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    ABSTRACT: The systematic modification of a nickel–titanium-alloy by annealing in a complex gas atmosphere was investigated. A mixture of HCl and H2O in inert argon was chosen. The reaction kinetics was investigated at 600 °C, 700 °C and 800 °C. The reaction kinetics displayed a significant dependence on the temperature. It was monitored by means of a thermogravimetric balance that showed a quasi-parabolic scale growth at 600 °C, a paralinear or so called Tedmon kinetic at 700 °C with a distinct weight maximum after about 35 h, and finally a linear evaporation kinetic at 800 °C. This behaviour is attributed to the concurrent reactions of oxidation, chloridation and evaporation of corrosion products. The kinetics of these reactions is different for the two alloying elements and with respect to the equiatomic composition they are coupled to each other. Cross sections prove that a stochiometric titanium depletion is achieved leading to the formation of a Ni3Ti layer (d = 50 μm) which is in turn covered by a pure titanium oxide layer (d = 40 μm). The applicability of this technique for tailored surfaces with a high degree of biocompatibility is discussed.
    Corrosion Science. 01/2008;
  • H. Asteman, M. Spiegel
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    ABSTRACT: The oxidation behaviour of a number of ferritic iron based commercial steels and model alloys containing 6 and 9 wt% Cr and 0–2.5 wt% Al have been studied at 700 °C. The oxidation time ranged from 5 min to 500 h and the atmosphere consisted of flowing dry synthetic air. The oxide layers formed were analysed by SEM, GI-XRD and ToF-SIMS. The material without Al formed a (Cr,Fe)2O3 film with an Fe enrichment in the outer part of the layer. The Al containing alloys showed more complex oxidation behaviour. The oxidation started initially by formation of (Cr,Fe)2O3 with an Cr enriched inner part. With time Al was oxidized and dissolved in the inner Cr rich part of the oxide. This process continued until it eventually was transformed into α-Al2O3 with minute amount of Fe in the outer and Cr in the inner part of the oxide. The thickness of all oxide films ranged from 20 to 400 nm apart from the material that contained 9% Cr and no Al, which experienced breakaway oxidation after 500 h at 700 °C. This means that materials alloyed with small amounts of Al must also be considered to be protective at 700 °C, as the thicknesses of the Al2O3 oxides was comparable with the ones not containing Al, and as they do not experience breakaway corrosion.
    Corrosion Science. 01/2008; 50(6):1734-1743.
  • Materials Science Forum 01/2008; 595-598:797.
  • Srinivasan Swaminathan, Michael Spiegel
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    ABSTRACT: Segregation and selective oxidation phenomena of minor alloying elements during annealing of steel sheets lead to the formation of bare spots after hot dip galvanizing. In order to understand the influence of common alloying elements on the surface chemistry after annealing, model alloys of binary (Fe–2Si, Fe–2Mn and Fe–0.8Cr), ternary (Fe–2Mn–2Si, Fe–2Mn–0.8Cr and Fe–2Si–0.8Cr) and quarternary (Fe–2Mn–2Si–0.8Cr) systems were investigated. The specimens were annealed for 60s at 820°C in N2–5% H2 gas atmospheres with different dew points −80 and −40°C, respectively. Surface chemistry of the annealed specimens was obtained by using X-ray photoelectron spectroscopy (XPS). The field emission scanning electron microscopy (FE-SEM) was used to view surface morphology. At low dew point −80°C, apart from the thermodynamical calculations such as solubility product of oxides and their critical solute concentrations, kinetics play a decisive role on the selective oxidation, i.e. oxygen competition. As expected, the amount of external selective oxidation of alloying elements are well pronounced at higher dew point −40°C. An attempt has been made to explain the dominant process of Si and Mn on Cr-oxidation and segregation. It is observed that annealing of quarternary system at higher dew point shifts the Cr-oxidation from external to internal.
    Applied Surface Science 01/2007; 253(10):4607-4619. · 2.54 Impact Factor
  • Source
    H. Asteman, M. Spiegel
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    ABSTRACT: The paper presents the results from an investigation studying the ability of pre-oxidized metals and alloys to withstand chlorine attack in the form of gaseous HCl. The materials under investigation were pure Fe (s), Cr (s), Ni (s), and a commercial 18Cr–10Ni–Fe (304) alloy. The samples were pre-oxidized in different well defined environments, dry 10vol.% O2 (g)+N2 (bal.), 10vol.% O2 (g)+5vol.% H2O (g)+N2 (bal.) and 10vol.% O2 (g)+250vppm SO2 (g)+N2 (bal.) for 24h at 400°C using a horizontal tube furnace. Afterwards the oxide films were characterized by GI-XRD, FEG-SEM, XPS and ToF-SIMS. The samples were then exposed further in 10vol.% O2 (g)+500vppm HCl (g)+x (x=5vol.% H2O (g), 250vppm SO2 (g))+N2 (bal.). The exposure time was 100h and after the exposures during the cool down process the reaction chamber was flushed with dry 10vol.% O2 (g)+N2 (bal.). The corroded samples were then examined by the same techniques mentioned before. HCl (g) showed mainly to be aggressive toward the Fe (s) samples that form a relatively thick and porous oxide scale consisting of layered Fe2O3 (s)/Fe3O4 (s) during pre-oxidation, and the aggressiveness did not depend on the pre-oxidation conditions. All the other materials formed thin and dense oxides (20–100nm) during pre-oxidation, and they did not suffer accelerated oxidation caused by HCl (g) during the subsequent exposure. The only exception was Ni (s) that had been pre-oxidized in an atmosphere containing SO2 (g), in this case Ni sulphides and sulphates were formed during pre-oxidation which in turn caused accelerated oxidation to Ni when subsequently exposed to HCl (g). HCl (g) readily reacts with NiSO4 (s) and Ni3S2 (s) and forms NiCl2 (s) and SO3 (g).
    Corrosion Science - CORROS SCI. 01/2007; 49(9):3626-3637.
  • Y.S. Li, Y. Niu, M. Spiegel
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    ABSTRACT: The corrosion behaviour of pure iron, pure chromium, and aluminium/silicon alloyed Fe–Cr materials was investigated at 650 °C in air accompanied by gaseous or solid KCl salt. The corrosion rates of these materials with KCl salt are high and they are strongly affected by the salt amount, the types of the alloying elements and the concentration of chromium. The dominant degradation mechanism for the chromia-forming alloys by KCl attack is the preferential formation of potassium chromate over the conventionally protective chromia, characterized by typical features of bubbles, cracks, volatility and severe spallation for the corrosion products. A detrimental effect of chromium is confirmed. Al-alloying addition to Fe–Cr alloys is beneficial by enhancing the corrosion resistance. Silicon is more effective in promoting the corrosion resistance of Fe–Cr alloys by forming a stable and dense oxide layer in the inner zone which suppresses the rapid growth of iron oxides.
    Corrosion Science. 01/2007; 49(4):1799-1815.
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    ABSTRACT: This study is a part of the FP5 Project entitled “Mitigation of Formation of Chlorine Rich Deposits Affecting Superheater Corrosion under Co-Combustion Conditions” (CORBI) which is aimed to improve the understanding of corrosion mechanisms in cases of biomass and waste combustion.The laboratory experiments, made at the JRC Plant Simulation Test Laboratory, are focused mainly on common ferritic and austenitic materials (X10, X20, 2.25Cr1Mo, AC66, Sanicro28, Esshette 1250, etc.), which are usually used in energy conversion systems. The experiments were carried out in multi-sample autoclaves at an isothermal temperature of 535 °C in various simulated combustion atmospheres (22% H2O + 5% O2 + xCO2 + N 2 with different CO2 content varying from 0 to 25 vol.%) on samples with and without filter/cyclone ash deposition. The results obtained show that the corrosion rate of the studied materials increases with increasing CO2 content in the atmosphere. Such behaviour was observed for samples with and without ash deposit.The detailed analysis and thermodynamic calculations of cyclone and filter ash behaviour were performed at MPIE in Duesseldorf. The ashes were exposed to 13% CO2 + 5% O2 + xH2O + y HCl + N2 atmospheres with different H2O content varying from 5–22% and HCl content varying from 0–200 ppm at 535 °C. The results obtained show that in an HCl-containing atmosphere the alkali chloride formed from alkali carbonate, as well as hydroxides and oxides, can additionally accelerate the oxidation process. In the HCl free atmosphere at increased H2O content, alkali carbonates and hydroxides can form, so enhanced alkali chloride induced oxidation will not occur.
    Materials and Corrosion 02/2006; 57(2):176 - 181. · 1.21 Impact Factor
  • S. C. Cha, M. Spiegel
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    ABSTRACT: Corrosion of superheaters caused by the deposition and subsequent reaction of alkali chloride containing ashes is one of the main material problems by combustion of biomass for energy conversion. The alkali chloride particles are formed during combustion and transported as aerosol or in the vapor phase within the combustion gas, subsequently sticking on the surface of the metallic tube. The initial reaction between the tube surface and the salt particle plays a major role in the initiation of the corrosion process and, therefore, are studied in detail in this work. The salt particles were locally deposited by means of thermophoresis within an aerosol generator, available at MPIE. Studies on the reaction of KCl particles with iron surfaces showed that a reaction takes place already at 300 °C. In N2-O2 atmospheres, the attack was very local, whereas the addition of 0.05 vol.% HCl to the reaction gas led to complete coverage of the iron surface with chloride. In contrast, reactions of KCl with nickel and chromium surfaces start to be significant only at 500 °C and higher. The paper summarizes the reaction behavior of Fe, Ni and Cr after thermophoretic deposition of KCl particles and subsequent reaction at elevated temperatures.
    Materials and Corrosion 02/2006; 57(2):159 - 164. · 1.21 Impact Factor
  • Andreas Ruh, Michael Spiegel
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    ABSTRACT: Thermogravimetric (TG) experiments have been carried out to study the kinetics of hot corrosion of Fe, Cr and Ni, covered by a molten KCl–ZnCl2 mixture of a composition close to the eutectic (50 mol% KCl–50 mol% ZnCl2). Furthermore binary and ternary phase diagrams were calculated in order to describe the corrosion process. The tests were conducted at a temperature of 320 °C in an atmosphere consisting of argon and oxygen. For iron different stages are observed in a TG curve. They can be attributed to the different reaction steps of iron chloride formation (incubation phase), oxide precipitation (linear stage) and scale formation (parabolic or logarithmic stage). Based on these observations a model, described by Spiegel [A. Spiegel, Molten Salt Forum 7 (2003) 253], is confirmed. For Cr and Ni these stages are not observed. At 8 vol% O2 only slight oxidation of Cr and Ni was observed accompanied by evaporation of the salt deposit. At 16 vol% O2 the rate of oxidation increases and the experiments yield a curve that is either parabolic or logarithmic for both Ni and Cr. As a result it is shown that the solubility of iron chloride in the KCl–ZnCl2 melt is higher than the solubility of nickel chloride and chromium (III) chloride in the KCl–ZnCl2 melt. This enables a higher diffusibility of iron chloride to the upper region of the melt where a higher oxygen partial pressure (p(O2)) is present leading to a higher oxidation rate of iron.
    Corrosion Science. 01/2006; 48(3):679-695.
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    ABSTRACT: The selective surface oxidation of the Ti-stabilized interstitial free (Ti-IF) and dual phase (DP) steel during recrystallization annealing at 820 °C under the variety of exposure time and composition of protective H2–N2 atmosphere at low dew point (−40 °C) was examined. It was found that Mn, Al, Si and Cr oxides are formed in all cases, but higher Mn and Si concentration in DP steel leads to an increase in a density of coarse nonwettable MnSiO3 particles. An increase in annealing time enhances surface coverage with oxides, while increased H2 content in gas atmosphere results in less coverage with external oxides improving the wettability. The influence of the stronger reducing atmosphere is more exhibit on Ti-IF steel where after 120 s of annealing in 15vol.%H2–85vol.%N2 atmosphere the wetting angle θ stabilized to a value of the order of 6°. The presence of surface BN and the TiN particles also affects the full surface coverage by external oxides.
    Corrosion Science. 01/2006;
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    ABSTRACT: The experimental endstation of the hard X-ray beamline BL9 of the Dortmund Electron Accelerator is equipped with a Huber six-circle diffractometer. It is dedicated to grazing-incidence X-ray diffraction and X-ray reflectivity experiments on solid surfaces and thin films as well as to powder diffraction measurements. A new set-up for grazing-incidence X-ray scattering of liquids has been built up using a silicon mirror to reflect the incident X-ray to the liquid surface at angles of incidence around the critical angle of total reflection of the sample. X-ray reflectivity measurements of a polymer film and grazing-incidence X-ray diffraction measurements of an epitaxically grown Gd40Y60 film, an oxidized surface of Fe-15at.% Al alloy and aqueous salt solutions are presented and discussed.
    Journal of Synchrotron Radiation 01/2006; 13(13):8. · 2.19 Impact Factor
  • S. C. Cha, M. Spiegel
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    ABSTRACT: Local reactions of NaCl particles with pure iron surfaces have been investigated to compare with the results of previous studies on the local reactions of KCl particles. Before short-term oxidation at various temperatures in N2–20 vol.-%O2–0·05 vol.-%HCl atmospheres, microscale NaCl particles were deposited by thermophoresis on bare iron surfaces and pre-oxidised samples. After reaction, the samples were examined using field emission microscopy (FEM), X-ray photoelectron spectroscopy (XPS) and chemical analysis. In particular, NaCl particles reacted with the iron surface at 300°C, depending on the gas phase composition. In N2–O2 atmospheres very local reactions took place, whereas the addition of 500 vppm HCl led to complete coverage of the iron surface with chloride. In addition, the reactions of KCl particles on nickel surfaces at 500°C have been investigated for comparison with those of KCl and NaCl particles on iron surfaces at 300°C.
    Corrosion Engineering Science and Technology 08/2005; 40(3):249-254. · 0.54 Impact Factor
  • M. Spiegel, I. Parezanović
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    ABSTRACT: Industrial annealing of automotive steel grades is carried out in order to improve the mechanical properties and to adjust the grain size. However, the surface chemistry changes drastically due to selective oxidation and segregation phenomena, which significantly influence the further surface treatment, i.e. hot dip galvanizing.The paper discusses results of laboratory experiments on selective oxidation and segregation of minor alloying elements Mn, Al, Cr and Si and non-metallic elements B, P and S during annealing of steel sheets in an N2-5%H2 atmosphere as a function of dew point. It will be shown that at lower dew points mostly external oxidation of Al and Mn occurs, where B shows a high tendency to segregate to the free surface and to form a BN film, especially observed on ferritic/austenitic steel. With increasing dew point, the oxidation of Al becomes internal and Mn, Si and Cr are oxidized externally. Boron also segregates to the surface by forming mixed Mn-B oxides and in the case of ferritic steels suppresses Si segregation and oxidation. The formation of phosphates by segregation of P becomes important at a D.P. of 0°C.
    Materials at High Temperatures 08/2005; 22(3-4):343-349. · 0.34 Impact Factor

Publication Stats

202 Citations
45.66 Total Impact Points

Institutions

  • 1995–2011
    • Max Planck Institute for Iron Research GmbH
      • Department of Interface Chemistry and Surface Engineering
      Düsseldorf, North Rhine-Westphalia, Germany
  • 2008
    • Salzgitter Mannesmann Forschung
      Duisburg-Hamborn, North Rhine-Westphalia, Germany