TY - CONF A1 - Stephan-Scherb, Christiane T1 - Elucidation of competitive oxidation/sulfidation reactions on binary ferritic alloys N2 - Ferritic-austenitic chromia-forming alloys are frequently used as boiler tubes and heat exchanger materials for fossil-,biomass, and co-fired power plants. In all applied environments several strongly corrosive gaseous species such as CO2, SO2, SO3, H2O, O2 exist, causing materials degradation by high-temperature corrosion. The elucidation of degradation mechanisms introduced by multiple gases is challenging due to the presence of different oxidizing agents contributing to the competing reactions for oxidation, sulfurization or carburization. The degradation processes can be divided into initial stages, a transitional stage and the further proceeding steady-state oxidation reaction. Especially the long-term steady-state oxidation and further materials’ life-time are strongly dependent on the initial stages. The adsorption and absorption of the reactive species at the alloy surface and the growing oxide in the initial reaction is further influenced by dissociation and re-reactions of the gas phase molecules. To understand these mechanisms from a fundamental point of view in more detail, dedicated experiments and advanced characterization techniques on various length scale need to be applied. Real-time approaches using highly energetic synchrotron X-ray diffraction showed a high potential to enlighten competitively mechanisms by following the corrosion reactions in-situ in the environment they occur. Despite various other thin film characterization techniques, time of flight secondary ion mass spectroscopy (ToF-SIMS) is a powerful tool to visualize light atoms or labeled isotopes enabling the Differentiation between different oxidizing species. It was especially shown to be applicable in challenging atmospheres containing KCl deposits or in CO/CO2/O2 environments. The present study analyses the competing oxidation/sulfidation process in a humid atmosphere on two ferritic alloys with 2 and 9 % in weight chromium by in situ energy dispersive X-ray diffraction (EDXRD) and comparative tube furnace exposure using S16O2 and H2 18O atmosphere. T2 - Conference on High Temperature Corrosion and Protection of Materials HTCPM 2021 CY - Online Meeting DA - 29.03.2021 KW - Oxidation KW - High Temperature Corrosion KW - Ferritic Alloys KW - SIMS KW - EDXRD PY - 2021 AN - OPUS4-52363 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Kramer, A. A1 - Nies, Daniel A1 - Pulz, Robert A1 - Rehmer, Birgit A1 - Stephan, Ina A1 - Maierhofer, Christiane ED - Mazal, Pavel T1 - Laser induced active thermography for the visualization of transport processes in building materials T2 - 5th International workshop of NDT experts - NDT in progress 2009 CY - Prague, Czech Republic DA - 2009-10-12 KW - Active thermography KW - Laser KW - Local thermal excitation KW - Thermal transport KW - Water transport KW - Wood preservatives PY - 2009 SN - 978-80-214-3968-9 SP - 153 EP - 162 AN - OPUS4-20337 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Harrer, Andrea A1 - Nies, Daniel A1 - Pulz, Robert A1 - Kervalishvili, Guram N. A1 - Rehmer, Birgit A1 - Stephan, Ina A1 - Maierhofer, Christiane T1 - Untersuchung von Transport- und Schädigungsprozessen mittels lokal angeregter aktiver Thermografie N2 - Als schnelles und berührungsfreies Messverfahren kann die aktive Thermografie auch in-situ eingesetzt werden, d.h. während sich Materialeigenschaften aufgrund direkter oder indirekter Einflüsse ändern. In diesem Beitrag stellen wir die Methode der aktiven Thermografie mittels lokaler Laseranregung und deren Anwendung auf unterschiedliche Materialien wie Holz, Sandstein und Keramiken vor. Mit der im Folgenden beschriebenen Methode wurden der Einfluss von Holzschutzmitteln auf die thermischen Eigenschaften von Holz, Feuchtetransportprozesse in Naturstein sowie die thermischen Eigenschaften von Siliziumcarbid unterschiedlicher Dicke und von Hochtemperaturkeramiken nach zunehmender thermischer Belastung in-situ untersucht. Experimentelle Ergebnisse werden u. a. im Vergleich mit numerischen Simulationen vorgestellt. T2 - DGZfP-Jahrestagung 2010 CY - Erfurt, Deutschland DA - 2010-05-10 PY - 2010 SN - 978-3-940283-26-9 IS - DGZfP-BB 122 (P36) SP - 1 EP - 9 CY - Berlin AN - OPUS4-21888 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Falk, Florian A1 - Menneken, M. A1 - Stephan-Scherb, Christiane T1 - Real-time observation of high- temperature gas corrosion in dry and wet SO2-containing atmosphere N2 - Sulfur and water have a fundamental impact on the corrosion rate and potential failure of materials. It is therefore necessary to understand the mechanisms, rates, and potential means of transport, as well as the reactions of these elements with an alloy. This paper investigates the effect of water vapor in the initial stages of SO2 corrosion of an Fe-9Cr-0.5Mn model alloy at 650°C in situ under laboratory conditions using energy-dispersive x-ray diffraction analysis. Two separate experiments were run, one with a 99.5% Ar + 0.5% SO2 atmosphere and one with a 69.5% Ar + 0.5% SO2 + 30% H2O atmosphere. With a wet atmosphere, the alloy formed a scale with decreasing oxygen content towards the scale–alloy interface. Sulfides were identified above and below a (Fe, Cr)3O4 layer in the inner corrosion zone. In contrast to this, the overall scale growth was slower in a dry SO2 atmosphere. KW - Early oxidation KW - Early sulfidation KW - Ferritic steels PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-472844 UR - https://link.springer.com/article/10.1007/s11837-019-03335-9#enumeration DO - https://doi.org/10.1007/s11837-019-03335-9 SN - 1047-4838 SN - 1543-1851 VL - 71 SP - 1 EP - 6 PB - Springer CY - New York AN - OPUS4-47284 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Marquardt, J. A1 - Gurieva, G. A1 - Stephan-Scherb, Christiane A1 - Schorr, S. T1 - The Effect of Copper Vacancies on the Anion Position of Chalcopyrite Type CuGaS2 N2 - The prediction of structural parameters and optoelectronic properties of compound semiconductors is very important. However, calculations often neglect chemical variability and structural defects. In chalcopyrite type semiconductors one of the major defects are copper vacancies (V Cu). The four cation neighbors of the anion determine its position in the chalcopyrite type structure expressed by the Wyckoff position 8d (x, 1/4, 1/8). Intrinsic point defects like V Cu and anti-sites may cause variations of the Anion position in the middle of the cation tetrahedron, especially in the Anion position Parameter x. For stoichiometric chalcopyrite type compounds a formalism according to the principle of conservation of tetrahedral bonds (CTB) can be applied to calculate the anion position parameter, but it fails in the case of off-stoichiometric chalcopyrites. This case study of chalcopyrite type CuGaS 2 and Mn-substituted GuGaS 2 shows that the experimentally determined anion position Parameter x deviate from values calculated by CTB approach. The systematic investigation of off-stoichiometric CuGaS 2 and Mn-substituted GuGaS 2 demonstrates the effect of copper vacancies on the average radii of the cation sites (Wyckoff positions 4a and 4b) as well as on the anion position Parameter x. By applying an elaborated CTB Approach implementing copper vacancies an agreement between experimental and calculated anion position Parameter x can be obtained. KW - Chalcogenides KW - Neutron diffraction KW - Copper vacancies PY - 2019 DO - https://doi.org/10.1002/pssa.201800882 VL - 216 IS - 15 SP - 1800882 PB - Wiley AN - OPUS4-47748 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stephan-Scherb, Christiane T1 - Elucidation of Surface Degradation Phenomena By In Situ X-ray techniques N2 - Presentation of in situ and real time approaches to study high temperature oxidation phenomena by adavnced X-ray techniques. Application to the analysis of degradation mechanisms of chemical complex alloys and high entropy alloys was presented. T2 - SPP 2006 Hot Topic Meeting "Large Scale Facility Based Techniques CY - Helmholtz-Zentrum Berlin für Materialien und Energie, Germany DA - 26.09.2019 KW - High entropy alloys KW - Diffraction KW - In situ KW - Oxidation PY - 2019 AN - OPUS4-49134 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Weber, Kathrin A1 - de Oliveira Guilherme Buzanich, Ana A1 - Radtke, Martin A1 - Reinholz, Uwe A1 - Stephan-Scherb, Christiane T1 - A µ‐XANES study of the combined oxidation/sulfidation of Fe–Cr model alloys N2 - The precise analysis of cation diffusion profiles through corrosion scales is an important aspect to evaluate corrosion phenomena under multicomponent chemical load, as during high‐temperature corrosion under deposits and salts. The present study shows a comprehensive analysis of cation diffusion profiles by electron microprobe analysis and microbeam X‐ray absorption near edge structure (µ‐XANES) spectroscopy in mixed oxide/sulfide scales grown on Fe–Cr model alloys after exposing them to 0.5% SO2. The results presented here correspond to depth‐dependent phase identification of oxides and sulfides in the corrosion scales by µ‐XANES and the description of oxidation‐state‐dependent diffusion profiles. Scales grown on low‐ and high‐alloyed materials show both a well‐pronounced diffusion profile with a high concentration of Fe3+ at the gas and a high concentration of Fe2+ at the alloy interface. The distribution of the cations within a close‐packed oxide lattice is strongly influencing the lattice diffusion phenomena due to their different oxidation states and therefore different crystal‐field preference energies. This issue is discussed based on the results obtained by µ‐XANES analysis. KW - X-ray absorption spectroscopy KW - Oxidation KW - Sulfidation PY - 2019 DO - https://doi.org/10.1002/maco.201810644 VL - 70 IS - 8 SP - 1360 EP - 1370 PB - Wiley VCH-Verlag AN - OPUS4-47934 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stephan-Scherb, Christiane T1 - Unravelling high temperature oxidation phenomena by in situ x-ray techniques N2 - Unravelling high temperature oxidation phenomena by in situ x-ray techniques. A multi techqnique approach to study high temperature gas corrosion is presented. T2 - Gordon Research Conference on High Temperature Corrosion CY - New London, NH, USA DA - 20.07.2019 KW - Corrosion KW - High temperature KW - Diffraction KW - Spectroscopy PY - 2019 AN - OPUS4-48772 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stephan-Scherb, Christiane T1 - Materialschädigung durch Hochtemperaturkorrosion von koventionellen und innovativen Legierungssystemen N2 - Konventionelle und innovative Hochtemperaturwerkstoffe sind im technischen Betrieb einer Vielzahl an Belastungen ausgesetzt. Neben mechanischen Beanspruchungen stellt die chemische Belastung durch das Vorhandensein von aggressiven und korrosiven Medien (SO2, CO2, O2, H2O…) bei hoher Temperatur einen Schlüsselfaktor dar, der die Langlebigkeit der Materialien im Einsatz beeinflusst. Neben konventionellen, mikroskopischen Analyseverfahren bieten röntgenbasierte Techniken Möglichkeiten, die Grenzflächenreaktionen zwischen dem Werkstoff und den Medien während der chemischen Belastung (in situ) zu untersuchen. Neuartige Einblicke in die zugrunde liegenden Prozesse der Schädigungsmechanismen werden anhand von klassischen ferritischen Legierungen beschrieben. Das Verständnis von Schlüsselfaktoren zur Induzierung eines Schutzmechanismus ist insbesondere für die Entwicklung von neuartigen Materialklassen wie Hochentropie- und chemisch komplexe Legierungen notwendig. Erste Einblicke in Schädigungsmechanismen durch Gaskorrosion dieser innovativen Materialsysteme werden vorgestellt. T2 - AWT-VDI Werkstofftechnik Arbeitskreis Bremen CY - Leibnitz Institut für Werkstofforientierte Technologien, Germany DA - 27.11.2019 KW - In situ KW - Heißgaskorrosion KW - Hochentropielegierungen KW - XRD PY - 2019 AN - OPUS4-49844 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stephan-Scherb, Christiane T1 - Early stages of high temperature oxidation/sulfidation studied by synchrotron x-ray diffraction and spectroscopy N2 - Ferritic high temperature alloys are widely used as boiler tube and heat exchanger materials in coal, biomass and co-fired power plants. All technologies have in common that the applied materials are exposed to different temperatures, process pressures and reactive atmospheres that lead to a change of the material properties and a further degradation of the material. Material changes caused by aging in highly corrosive and toxic gases such as SO2 are mainly studied ex situ after the reaction is finished. The solid material is deposited in the atmosphere for a certain period of time, and material changes are then examined by various microscopic techniques such as optical microscopy (OM), electron microprobe analysis (EMPA), scanning electron microscopy (SEM and TEM) and X-ray diffraction (XRD). Nevertheless, extensive efforts were made to study material changes of high temperature alloys under oxidizing and reducing atmospheres by environmental scanning electron microscopy or in situ TEM techniques However, the possibilities of microscopic in situ techniques are very limited for the use of highly corrosive and toxic gases such as SO2. Since Sulfur induced corrosion at temperatures relevant for coal and biomass fired power plants, which is causing breakaway oxidation and sulfide precipitation at grain boundaries, is still of scientific interest, the current work focuses on the effect of SO2 in an initial stage of corrosion of ferritic alloys. For the analysis of early stages of combined oxidation and sulphidation processes of Fe-Cr model alloys the usage of a light furnace to conduct a rapid reactive annealing experiment is feasible. Previous studies presented distinct results of the influence of chromium on early high temperature corrosion by SO2 by this technique and subsequent classical metallographic analyses. However, it is still not possible to trace the corrosion mechanism in real time by conducting single aging experiments. The current work introduces two different approaches to study the initial stages of high temperature oxidation processes by applying above state of the art X-ray diffraction and spectroscopy methods. One part focuses on the real time observation of the formation of corrosion products such as oxides and sulfides by energy dispersive X-ray diffraction (EDXRD). The potential of this technique to study crystallization and growth processes of thin films in a reactive environment in real time was previously shown for different compound semiconductors. This approach was now applied to follow oxidation and sulphidation processes of ferritic model alloys in SO2 and SO2/H2O environments. The diffraction signals of the X-rays were detected during the corrosion process and the peak area and positions were analyzed as a function of time. This procedure enables monitoring external oxide growth and material loss in real time in an early stage of corrosion. The other part of the current work presents the possibilities of X-ray absorption near edge structure spectroscopy (XANES) to characterize oxide scales and their growth mechanisms. Precise phase identification and quantification of corrosion products in a multi-phase oxide/sulfide scale is a pre-requisite to understand diffusion paths of metal ions and gas components. It is a challenging task to distinguish structurally similar reaction products such as Fe3O4 and FeCr2O4 especially in thin films with texture effects by diffraction. To illustrate for example Cr-out diffusion of an alloy throughout an inner and external oxide scale the differentiation of Fe3O4 and FeCr2O4 is indispensable. XANES uses the photoionization effect at the metal absorption edge in an aging product and accesses by this structural and chemical information. The current work uses XANES at the Fe-K and Cr-K absorption edge to identify various aging products grown as thin layers on alloys after short time aging experiments. A reaction chamber for combining high temperature oxidation experiments with surface sensitive X-ray absorption near edge structure spectroscopy will be introduced and first results of XANES on scales at high temperatures will be presented. T2 - ISHOC 2018 CY - Matsue, Japan DA - 22.10.2018 KW - Corrosion KW - Sulfidation KW - In situ KW - Diffraction KW - XANES PY - 2018 AN - OPUS4-47278 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stephan-Scherb, Christiane T1 - High temperature oxidation/sulfidation meets X-ray absorption near edge structure spectroscopy (XANES) N2 - Ferritic-martensitic alloys with 12-16 % Cr in weight are subject to devices for various energy systems, such as coal power plants and waste incineration plants. These materials are exposed to a highly corrosive environment which lead to a degradation of the material. Especially the simultaneous oxidation and sulfidation is thereby of special interest. Proper spatially resolved measurements that determine not only chemical compositions but phases are rare. However, precise phase identification and quantification of corrosion products within the multi-phase corrosion scales is a key aspect to understand diffusion paths of metal ions and gas ions/molecules. This study investigated Fe-Cr model alloys with Cr contents from 0 to 13 % in weight in 0.5 % SO2 and 99.5 % Ar atmosphere to aim in a fundamental and systematic analysis. Samples were aged at 650 °C for time scales from 12 h to 250 h. The results presented here correspond to depth dependent phase identification of oxide and sulphide phases in the corrosion scales by using X-ray absorption near edge spectroscopy (XANES). Per sample a series of ca. 20 spots (1-5 µm spot size) from scale-gas to scale-metal interface were measured. XANES spectroscopy was performed at the Fe-K edge (7.11 keV) on polished cross sections. The collected spectra were fitted to a combination of reference materials to quantify the present phases at different positions within the scale.The phase distribution differs with Cr content and the Cr diffusion through pure Fe-oxide and mixed Fe-Cr-oxide phases is discussed. T2 - EFC Workshop "High Temperature Corrosion" CY - Frankfurt am Main, Germany DA - 26.09.2018 KW - High temperature corrosion KW - XANES PY - 2018 AN - OPUS4-47277 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Falk, Florian A1 - Sobol, Oded A1 - Stephan-Scherb, Christiane T1 - The impact of the microstructure of Fe-16Cr-0.2C on high-temperature oxidation – sulphidation in SO2 N2 - This study elucidates the impact of the microstructure of Fe-16Cr-0.2C on oxide layer formation at 650 ◦C in Ar-0.5 % SO2. A cold-rolled and two heat-treated states of the alloy were exposed for up to 1000 h. The samples were characterised in detail from microstructural and chemical perspectives using scanning electron microscopy (SEM), X-ray diffraction (XRD) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The microstructural modification of the alloy by heat-treatment was advantageous. It was found that Cr-carbides support chromia formation and reduce sulphidation when their area fraction is low and diameter is small. KW - Steel KW - Iron KW - SIMS KW - SEM KW - High temperature corrosion KW - Oxidation KW - Sulphidation PY - 2021 DO - https://doi.org/10.1016/j.corsci.2021.109618 VL - 190 SP - 109618 PB - Elsevier Ltd. AN - OPUS4-53001 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -