TY - JOUR A1 - Griesche, Axel A1 - Pfretzschner, B. A1 - Taparli, Ugur Alp A1 - Kardjilov, N. T1 - Time-Resolved Neutron Bragg-Edge Imaging: A Case Study by Observing Martensitic Phase Formation in Low Temperature Transformation (LTT) Steel during GTAW N2 - Polychromatic and wavelength-selective neutron transmission radiography were applied during bead-on-plate welding on 5 mm thick sheets on the face side of martensitic low transformation temperature (LTT) steel plates using gas tungsten arc welding (GTAW). The in situ visualization of austenitization upon welding and subsequent α’-martensite formation during cooling could be achieved with a temporal resolution of 2 s for monochromatic imaging using a single neutron wavelength and of 0.5 s for polychromatic imaging using the full spectrum of the beam (white beam). The spatial resolution achieved in the experiments was approximately 200 µm. The transmitted monochromatic neutron beam intensity at a wavelength of λ = 0.395 nm was significantly reduced during cooling below the martensitic start temperature Ms since the emerging martensitic phase has a ~10% higher attenuation coefficient than the austenitic phase. Neutron imaging was significantly influenced by coherent neutron scattering caused by the thermal motion of the crystal lattice (Debye–Waller factor), resulting in a reduction in the neutron transmission by approx. 15% for monochromatic and by approx. 4% for polychromatic imaging. KW - Austenite-to-martensite transformation KW - Neutron radiography KW - Bragg-edge imaging KW - Gas tungsten arc welding (GTAW) KW - Debye–Waller factor KW - Low transformation temperature (LTT) steel PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-538016 DO - https://doi.org/10.3390/app112210886 VL - 11 IS - 22 SP - 10886 PB - MDPI CY - Basel AN - OPUS4-53801 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Griesche, Axel A1 - Pfretzschner, Beate A1 - Taparli, Ugur Alp A1 - Kardjilov, N. T1 - Time-Resolved Neutron Bragg-Edge Imaging: A Case Study by Observing Martensitic Phase Formation in Low Temperature Transformation (LTT) Steel during GTAW N2 - Polychromatic and wavelength-selective neutron transmission radiography were applied during bead-on-plate welding on 5 mm thick sheets on the face side of martensitic low transformation temperature (LTT) steel plates using gas tungsten arc welding (GTAW). The in situ visualization of austenitization upon welding and subsequent α’-martensite formation during cooling could be achieved with a temporal resolution of 2 s for monochromatic imaging using a single neutron wavelength and of 0.5 s for polychromatic imaging using the full spectrum of the beam (white beam). The spatial resolution achieved in the experiments was approximately 200 µm. The transmitted monochromatic neutron beam intensity at a wavelength of λ = 0.395 nm was significantly reduced during cooling below the martensitic start temperature M s since the emerging martensitic phase has a ~10% higher attenuation coefficient than the austenitic phase. Neutron imaging was significantly influenced by coherent neutron scattering caused by the thermal motion of the crystal lattice (Debye–Waller factor), resulting in a reduction in the neutron transmission by approx. 15% for monochromatic and by approx. 4% for polychromatic imaging. KW - Neutron radiography KW - Debye–Waller factor KW - Austenite-to-martensite transformation KW - Low transformation temperature (LTT) steel KW - Bragg-edge imaging KW - Gas tungsten arc welding (GTAW) PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-559077 DO - https://doi.org/10.3390/app112210886 VL - 11 IS - 22 PB - MDPI AN - OPUS4-55907 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jamro, R. A1 - Mente, Tobias A1 - Kardjilov, N. A1 - Markötter, Henning A1 - Al-Falahat, Ala'A. M. A1 - Woracek, R. A1 - Manke, I. A1 - Griesche, Axel T1 - Temperature distribution during welding measured by neutron imaging N2 - This study was carried out to investigate the neutron transmission signal as a function of sample temperature during a welding process. A theoretical description that includes the Debye-Waller factor was used to describe the temperature influence on the neutron crosssections. Neutron imaging using a monochromatic beam helps to observe transmission variations related to the material temperature. In-situ neutron imaging of welding experiments show the distribution of the temperature in bulk steel samples. The performed finite element modelling of expected temperature distributions shows good agreement with the obtained experimental data. KW - Neutron imaging KW - Debye-Waller-Faktor PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-586268 DO - https://doi.org/10.1088/1742-6596/2605/1/012026 VL - 2605 SP - 1 EP - 10 PB - IOP Publishing Ltd. AN - OPUS4-58626 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Laquai, René A1 - Schaupp, Thomas A1 - Griesche, Axel A1 - Müller, Bernd R. A1 - Kupsch, Andreas A1 - Hannemann, Andreas A1 - Kannengießer, Thomas A1 - Bruno, Giovanni T1 - Quantitative analysis of hydrogen-assisted microcracking in duplex stainless steel through X-ray refraction 3D imaging N2 - While the problem of the identification of mechanisms of hydrogen assisted damage has and is being thoroughly studied, the quantitative analysis of such damage still lacks suitable tools. In fact, while, for instance, electron microscopy yields excellent characterization, the quantitative analysis of damage requires at the same time large field-of-views and high spatial resolution. Synchrotron X-ray refraction techniques do possess both features. In this work, we show how synchrotron X-ray refraction computed tomography (SXRCT) can quantify damage induced by hydrogen embrittlement in a lean duplex steel, yielding results that overperform even those achievable by synchrotron X-ray absorption computed tomography. As already reported in literature, but this time using a non-destructive technique, we show that the hydrogen charge does not penetrate to the center of tensile specimens. By the comparison between virgin and hydrogen-charged specimens, we deduce that cracks in the specimen bulk are due to the rolling process rather than hydrogen-assisted. We show that (micro)cracks propagate from the surface of tensile specimens to the interior with increasing applied strain, and we deduce that a significant crack propagation can only be observed short before rupture. KW - 2101 duplex stainless steel KW - Hydrogen embrittlement KW - Synchrotron radiation KW - X-ray refraction KW - Computed tomography KW - Microcracking PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-542811 DO - https://doi.org/10.1002/adem.202101287 SN - 1438-1656 SP - 1 EP - 10 PB - Wiley-VCH CY - Weinheim AN - OPUS4-54281 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pfretzschner, Beate A1 - Schaupp, Thomas A1 - Hannemann, Andreas A1 - Schultz, Michael A1 - Griesche, Axel T1 - On the Genesis of Artifacts in Neutron Transmission Imaging of Hydrogenous Steel Specimens N2 - Hydrogen-charged supermartensitic steel samples were used to systematically investigate imaging artifacts in neutron radiography. Cadmium stencils were placed around the samples to shield the scintillator from excessive neutron radiation and to investigate the influence of the backlight effect. The contribution of scattered neutrons to the total detected intensity was investigated by additionally varying the sample-detector distance and applying a functional correlation between distance and intensity. Furthermore, the influence of the surface roughness on the edge effect due to refraction was investigated. KW - Refraction KW - Neutron imaging KW - Hydrogen KW - Supermartensitic steel KW - Backlight KW - Scattering PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-506587 DO - https://doi.org/10.3390/jimaging6040022 VL - 6 IS - 22 SP - 1 EP - 10 PB - MDPI CY - Basel, Switzerland AN - OPUS4-50658 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Quackatz, Lukas A1 - Griesche, Axel A1 - Kannengießer, Thomas T1 - Spatially resolved EDS, XRF and LIBS measurements of the chemical composition of duplex stainless steel welds: A comparison of methods N2 - Duplex stainless steels (DSS) are used in all industries where corrosion problems play a major role. Examples include the chemical industry, the food industry and shipping industries. DSS have a balanced phase ratio of ferrite (α) and austenite (γ). Unlike single-phase stainless steels, DSS combine the advantages of these and can therefore fit many industry requirements, such as weight saving or high mechanical strength. When these steels are welded, alloying elements can burn off and condense as thin layers on cold surface regions. This loss of chemical elements can lead to changes in the microstructure. With the help of Laser-Induced Breakdown Spectroscopy (LIBS), chemical element distributions were visualized. The results were compared with those of conventional measurement methods, such as energy dispersive X-ray analysis (EDS) and X-ray fluorescence analysis (XRF), and the results from LIBS could be validated. LIBS is suitable as a fast, straightforward measurement method for producing line scans along the weld seam and provides spatially resolved information on accumulation phenomena of burned off alloying elements. LIBS is very well suited for the detection of sub-surface elements due to the exclusively superficial ablation of the material. In addition, the measurement method has been calibrated so that quantitative statements about element concentrations can also be made. T2 - EMSLIBS 2021 CY - Online Meeting DA - 25.11.2021 KW - LIBS KW - TIG welding KW - Duplex stainless steel KW - XRF KW - EDS PY - 2022 DO - https://doi.org/10.1016/j.sab.2022.106439 SN - 0584-8547 VL - 193 SP - 1 EP - 8 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-54837 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Quackatz, Lukas A1 - Griesche, Axel A1 - Kannengießer, Thomas T1 - Rapid solidification during welding of duplex stainless steels – in situ measurement of the chemical concentration by Laser-Induced Breakdown Spectroscopy (LIBS) N2 - Duplex stainless steels (DSS) are frequently used, especially in applications requiring high strength combined with high corrosion resistance in aggressive media. Examples include power plant components and maritime structures. During welding of these steels, local variations in chemical composition can occur. This results in ferritization of the material and negatively affects the mechanical properties of the components. In this work, tungsten inert gas (TIG) welding experiments were performed with DSS. Chemical composition analysis was realized in situ by using Laser Induced Breakdown Spectroscopy (LIBS). The aim of the work is to quantitatively measure the chemical composition in the weld seam of various DSS and to identify possible influences of welding parameters on the microstructure of the material. The chemical concentrations of the main alloying elements Cr, Ni, Mn on the surface of the sample during the welding process and the cooling process were measured. Mn and Ni are austenite stabilizers and their content increases during welding by using certain high alloyed filler material. Spectra were recorded every 1.3 s at a spacing of approximately 2 mm. During the cooling process the location of the measurement was not changed. The LIBS method is proofed to be suitable for the quantitative representation of the chemical compositions during the welding process. T2 - ICASP-6 CY - Le Bischenberg, France DA - 20.06.2022 KW - LIBS KW - In situ measurement KW - Duplex stainless steel KW - TIG welding KW - Evaporation PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-571308 DO - https://doi.org/10.1088/1757-899X/1274/1/012018 VL - 1274 SP - 1 EP - 8 PB - IOP Publishing CY - Bristol AN - OPUS4-57130 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Quackatz, Lukas A1 - Griesche, Axel A1 - Nietzke, Jonathan A1 - Kannengießer, Thomas T1 - In situ measurement of hydrogen concentration in steel using laser‑induced breakdown spectroscopy (LIBS) N2 - The ISO 3690 standard “Determination of hydrogen content in arc weld metal” requires a thermal activation of the diffusible hydrogen in a piece of weld metal for the subsequent ex situ concentration measurement by carrier gas hot extraction CGHE or thermal desorption spectroscopy (TCD). Laser-induced breakdown spectroscopy (LIBS) offers a time and spatially resolved, almost non-destructive, in situ measurement of hydrogen at surfaces without sample preparation. We measured hydrogen in steels, which were charged either electrochemically or by high-pressure hydrogen gas, and compared the results. Further, the feasibility of quantitative hydrogen line scan measurements with LIBS was demonstrated by measuring hydrogen at water jet cut surfaces. The hydrogen concentrations measured with the help of LIBS were compared with CGHE measurements. It was observed that hydrogen can be reliably measured with LIBS for concentrations larger than 2 wt.-ppm. The maximum hydrogen concentration achieved using electrochemical charging was 85.1 ppm. The results show that LIBS is a promising technique for time- and spatially resolved measurements of hydrogen in steels. T2 - IIW Annual Assembly 2023 CY - Singapore KW - LIBS KW - Hydrogen measurement KW - Welding KW - Stainless steel KW - Diffusible hydrogen PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-593664 DO - https://doi.org/10.1007/s40194-023-01677-2 SP - 1 EP - 9 PB - Springer AN - OPUS4-59366 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Quackatz, Lukas A1 - Westin, Elin Marianne A1 - Griesche, Axel A1 - Kromm, Arne A1 - Kannengießer, Thomas A1 - Treutler, Kai A1 - Wesling, Volker A1 - Wessman, Sten T1 - Assessing ferrite content in duplex stainless weld metal: WRC ‘92 predictions vs. practical measurements N2 - AbstractThe weldability of stainless steels is largely controlled by the chemical composition, and alloys with ferritic or ferritic-austenitic solidification show the highest resistance to hot cracking. As the resulting phase balance also affects the final properties, it may be beneficial to both foresee and measure the weld metal ferrite content. The WRC ‘92 constitution diagram is currently the most accurate prediction tool available, but it does not take the cooling rate into consideration and the precision may be less accurate for stainless steels with high ferrite numbers (FNs). This study aims to assess the reliability of the WRC ‘92 diagram for weld metals with FN  50. The chemical composition was altered through gas tungsten arc welding (GTAW) of UNS S32205 with ER347 filler wire that had been coated using physical vapor deposition (PVD) with either niobium (Nb), copper (Cu), nickel (Ni), manganese (Mn), carbon (C), or silicon (Si). The actual ferrite content was evaluated using image analysis, FeriteScope and X-ray diffraction (XRD). While predictions from the WRC ‘92 diagram were deemed acceptable for Ni, Si, and Mn, notable deviations were observed for Nb, Cu, and C. The FeriteScope exhibited a consistent trend with image analysis, albeit with slightly higher FN values, wider scatter, and the conversion factor from FN to vol% is open for discussion. The lowest accuracy and largest spread were obtained using non-contact XRD, rendering it unsuitable for ferrite measurements of welds. These findings underscore the need for improved prediction tools and appropriate measurement methods for assessing ferrite content in duplex weld metals. KW - Duplex stainless steel KW - Welding KW - Phase balance KW - Microscopy KW - Microstructure PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-618777 DO - https://doi.org/10.1007/s40194-024-01878-3 SN - 1878-6669 VL - 69 IS - 1 SP - 31 EP - 45 PB - Springer CY - Berlin AN - OPUS4-61877 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Quackatz, Lukas A1 - Westin, Elin Marianne A1 - Griesche, Axel A1 - Kromm, Arne A1 - Kannengießer, Thomas A1 - Treutler, Kai A1 - Wesling, Volker A1 - Wessman, Sten T1 - Assessing ferrite content in duplex stainless weld metal: WRC ‘92 predictions vs. practical measurements N2 - AbstractThe weldability of stainless steels is largely controlled by the chemical composition, and alloys with ferritic or ferritic-austenitic solidification show the highest resistance to hot cracking. As the resulting phase balance also affects the final properties, it may be beneficial to both foresee and measure the weld metal ferrite content. The WRC ‘92 constitution diagram is currently the most accurate prediction tool available, but it does not take the cooling rate into consideration and the precision may be less accurate for stainless steels with high ferrite numbers (FNs). This study aims to assess the reliability of the WRC ‘92 diagram for weld metals with FN  50. The chemical composition was altered through gas tungsten arc welding (GTAW) of UNS S32205 with ER347 filler wire that had been coated using physical vapor deposition (PVD) with either niobium (Nb), copper (Cu), nickel (Ni), manganese (Mn), carbon (C), or silicon (Si). The actual ferrite content was evaluated using image analysis, FeriteScope and X-ray diffraction (XRD). While predictions from the WRC ‘92 diagram were deemed acceptable for Ni, Si, and Mn, notable deviations were observed for Nb, Cu, and C. The FeriteScope exhibited a consistent trend with image analysis, albeit with slightly higher FN values, wider scatter, and the conversion factor from FN to vol% is open for discussion. The lowest accuracy and largest spread were obtained using non-contact XRD, rendering it unsuitable for ferrite measurements of welds. These findings underscore the need for improved prediction tools and appropriate measurement methods for assessing ferrite content in duplex weld metals. KW - Duplex stainless steel KW - Phase fraction prediction KW - WRC diagram PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-623682 DO - https://doi.org/10.1007/s40194-024-01878-3 VL - 69 SP - 31 EP - 45 PB - Springer Science and Business Media LLC AN - OPUS4-62368 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -