TY - JOUR A1 - Griesche, Axel A1 - Dabah, Eitan A1 - Kardjilov, N. A1 - Hilger, A. A1 - Manke, I. A1 - Kannengießer, Thomas T1 - Imaging of hydrogen in steels using neutrons N2 - We investigated the hydrogen distribution spatially and temporally in technical iron at room temperature. Samples were charged electrochemically and subsequently analysed by means of neutron radiography and tomography. The radiographic images allowed for a time-resolved analysis of hydrogen fluxes. The three-dimensional distribution of hydrogen measured by neutron tomography delivered valuable information for the damage analysis of hydrogen-induced cracks. For the first time hydrogen concentration gradients inside the material could be detect directly together with the cracks. The neutron radiography and tomography results were gained at the Research Reactor BER II of the HZB in Berlin. KW - Hydrogen embrittlement KW - Hydrogen diffusion KW - Neutron tomography KW - Blister PY - 2014 DO - https://doi.org/10.3139/146.111043 SN - 1862-5282 VL - 105 IS - 7 SP - 640 EP - 644 PB - Carl Hanser CY - München AN - OPUS4-31084 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 - Taparli, Ugur Alp A1 - Jacobsen, Lars A1 - Griesche, Axel A1 - Michalik, Katarzyna A1 - Mory, David A1 - Kannengießer, Thomas T1 - In situ laser-induced breakdown spectroscopy measurements of chemical compositions in stainless steels during tungsten inert gas welding N2 - A laser-induced breakdown spectroscopy (LIBS) system was combined with a bead-on-plate Tungsten Inert Gas (TIG) welding process for the in situ measurement of chemical compositions in austenitic stainless steels during welding.Monitoring the weld pool's chemical composition allows governing the weld pool solidification behavior, and thus enables the reduction of susceptibility to weld defects. Conventional inspection methods for weld seams (e.g. ultrasonic inspection) cannot be performed during the welding process. The analysis system also allows in situ study of the correlation between the occurrence ofweld defects and changes in the chemical composition in theweld pool or in the two-phase regionwhere solid and liquid phase coexist. First experiments showed that both the shielding Ar gas and the welding arc plasma have a significant effect on the selected Cr II, Ni II and MnII characteristicemissions, namely an artificial increase of intensity values via unspecific emission in the spectra. In situ investigations showed that this artificial intensity increase reached a maximum in presence of weld plume. Moreover, an explicit decay has been observedwith the termination of thewelding plumedue to infrared radiation during sample cooling. Furthermore, LIBS can be used after welding to map element distribution. For austenitic stainless steels,Mnaccumulations on both sides of theweld could be detected between the heat affected zone (HAZ) and the base material. T2 - th International Conference on Laser-Induced Breakdown Spectroscopy (LIBS) CY - Chamonix-Mont-Blanc, France DA - 12.09.2016 KW - LIBS KW - TIG KW - Welding KW - Austenitic KW - Stainless steels KW - Chemical composition KW - In situ KW - Measurement PY - 2018 UR - http://www.sciencedirect.com/science/article/pii/S0584854717301064 DO - https://doi.org/10.1016/j.sab.2017.11.012 SN - 0584-8547 VL - 139 SP - 50 EP - 56 PB - Elsevier CY - Amsterdam, Niederlande AN - OPUS4-43122 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Griesche, Axel A1 - Dabah, Eitan A1 - Hilger, A. A1 - Kardjilov, N. A1 - Manke, I. A1 - Kannengießer, Thomas T1 - Neutron imaging of hydrogen in steels N2 - Transmission images with neutrons show a high contrast between hydrogen and iron when using state-of-the-art scintillator materials and digital Cameras. Monitoring the 2D hydrogen distribution evolution with good temporal resolution is possible if a high flux of neutrons is provided. The mass transport of hydrogen can be quantified by Converting the intensity distribution of the images in a hydrogen concentration distribution by using Standards with known composition and similar thickness. Then neutron radiography can be used quantitatively as a non-destructive measurement technique to determine diffusion coefficients e.g. for hydrogen in Steel. We report about measurements at Research Reactors in Germany. The capabilities and limitations, s well as perspectives of this method will be discussed and illustrated with selected examples. T2 - Materials Science & Technology (MS&T) 2013 CY - Montreal, Quebec, Canada DA - 27.10.2013 KW - Neutron radiography KW - Hydrogen KW - Diffusion KW - Steel PY - 2013 SP - 945 EP - 950 PB - Curran CY - Red Hook, NY AN - OPUS4-29506 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Griesche, Axel A1 - Solórzano, E. A1 - Beyer, Katrin A1 - Kannengießer, Thomas T1 - The advantage of using in-situ methods for studying hydrogen mass transport: Neutron radiography vs. carrier gas hot extraction N2 - Neutron radiography (NR) is compared with the commonly used carrier gas hot extraction (CGHE) technique. We performed isothermal hydrogen effusion experiments at 623 K to study the mass transport kinetics. The investigated material was technical iron. The quantification of the hydrogen mass flow is done for NR by using concentration standards. The temporal hydrogen concentration evolution in the sample coincides well for both methods, i.e. NR and CGHE, and is in good agreement with literature. The advantages of the NR method are the non-destructive nature of measuring and the in-situ determination of hydrogen concentrations with high spatial and temporal resolution. Remaining hydrogen inside the sample can be identified directly by the NR method. KW - Hydrogen diffusion KW - In-situ KW - Neutron radiography KW - Carrier gas hot extraction KW - Imaging PY - 2013 DO - https://doi.org/10.1016/j.ijhydene.2013.08.145 SN - 0360-3199 VL - 38 IS - 34 SP - 14725 EP - 14729 PB - Elsevier Ltd. CY - Oxford AN - OPUS4-29413 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Griesche, Axel A1 - Dabah, Eitan A1 - Kannengießer, Thomas A1 - Kardjilov, N. A1 - Hilger, A. A1 - Manke, I. T1 - Three-dimensional imaging of hydrogen blister in iron with neutron tomography N2 - We investigated hydrogen embrittlement and blistering in electrochemically hydrogen-charged technical iron samples at room temperature. Hydrogen-stimulated cracks and blisters and the corresponding hydrogen distributions were observed by neutron tomography. Cold neutrons were provided by the research reactor BER II to picture the sample with a spatial resolution in the reconstructed three-dimensional model of ~25 µm. We made the unique observation that cracks were filled with molecular hydrogen and that cracks were surrounded by a 50 µm wide zone with a high hydrogen concentration. The zone contains up to ten times more hydrogen than the bulk material. The hydrogen enriched zone can be ascribed to a region of increased local defect density. Hydrogen also accumulated at the sample surface having the highest concentration at blistered areas. The surfaces of the brittle fractured cracks showed micropores visualized by scanning electron microscopy. The micropores were located at grain boundaries and were surrounded by stress fields detected by electron backscattered diffraction. The cracks clearly originated from the micropores. KW - Hydrogen embrittlement KW - Hydrogen diffusion KW - In situ KW - Neutron tomography KW - Iron PY - 2014 DO - https://doi.org/10.1016/j.actamat.2014.06.034 SN - 1359-6454 SN - 1873-2453 VL - 78 SP - 14 EP - 22 PB - Elsevier Science CY - Kidlington AN - OPUS4-31068 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Griesche, Axel A1 - Dabah, Eitan A1 - Kannengießer, Thomas T1 - Neutron imaging of hydrogen in iron and steel N2 - Neutron radiography and tomography have been used for a time resolved in situ analysis and a 3D mapping of hydrogen diffusion in iron and steel. Samples were electrochemically charged with hydrogen and afterwards neutron transmission images were taken. Hydrogen diffusion coefficients in duplex stainless steel were determined at 623 K by measuring and comparing the sample's mean intensity with a hydrogen-free reference sample and subsequent normalisation to standards with known hydrogen content. In technical iron and in supermartensitic stainless steel the hydrogen distributions have been investigated. The radiographic images in iron show blisters, cracks and the distribution of molecular hydrogen inside cracks. The analysis of the diffusion behaviour of hydrogen out of a blister illustrates the capabilities of the method with respect to time and spatial resolution. The neutron tomography of supermartensitic tensile stressed samples illustrates the capability to visualise hydrogen distributions three-dimensionally. ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- On a utilisé la radiographie neutronique et la tomographie pour une analyse in situ à résolution temporelle et une cartographie 3D de la diffusion de l'hydrogène dans le fer et l'acier. On a chargé des échantillons par électrochimie avec de l'hydrogène et ensuite on a pris des images par émission de neutrons. On a déterminé les coefficients de diffusion de l’hydrogène dans l'acier inoxydable duplex à 623 K en mesurant et en comparant l'intensité moyenne de l'échantillon avec un échantillon de référence sans hydrogène et une normalisation subséquente à des échantillons références à teneur connue en hydrogène. On a examiné la distribution d'hydrogène dans le fer technique et dans l'acier inoxydable supermartensitique. Les images radiographiques du fer montrent des soufflures, des fissures, et la distribution de l'hydrogène moléculaire à l'intérieur des fissures. L'analyse du comportement de diffusion de l'hydrogène hors d'une soufflure illustre les possibilités de la méthode par rapport à la résolution temporelle et spatiale. La tomographie neutronique des échantillons supermartensitiques chargés en traction illustre la capacité de visualiser les distributions d'hydrogène en trois dimensions. KW - Neutron radiography KW - Hydrogen KW - Diffusion KW - Iron KW - Steel KW - Blister KW - Hydrogen assisted cracking PY - 2015 DO - https://doi.org/10.1179/1879139514Y.0000000162 SN - 0008-4433 VL - 54 IS - 1 SP - 38 EP - 42 PB - Canadian Institute of Mining and Metallurgy CY - Montreal AN - OPUS4-32809 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gollnow, C. A1 - Griesche, Axel A1 - Weidemann, Jens A1 - Kannengießer, Thomas T1 - Influence of external loads on a characteristic angle between grains and solidus line as an indicator for hot cracking susceptibility during GTA welding N2 - A long list of criteria determining the hot cracking susceptibility already exists. A main influence on solidification cracking can result from the design of the welded construction, i.e. from the influence of external loads. Using the Controlled Tensile Weldability (CTW) test, an external load hot cracking test, the influence of constant pre-load and different extension rates on the solidification cracking behavior of GTA (Gas Tungsten Arc) welds in an austenitic (AISI 309) and a ferritic (AISI 441) steel were investigated. Compared to specimens welded allowing free shrinkage and welded with an applied constant tensile pre-load, the specimens welded during the application of increasing tensile load show solidification cracks. In the weld seams, a characteristic angle α between the predominantly columnar grains and the fusion line can be observed. Specimens showing solidification cracks show a significantly larger angle α compared to the crack-free specimens. Based on these observations, the characteristic angle α is proposed as a new hot cracking criterion. KW - Hot cracking KW - External load test KW - Component design KW - Crack criterion KW - Grain growth PY - 2017 DO - https://doi.org/10.1016/j.jmatprotec.2016.08.013 VL - 239 SP - 172 EP - 177 PB - Elsevier AN - OPUS4-37278 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Boateng, Francis Twumasi A1 - Ewert, Uwe A1 - Kannengießer, Thomas A1 - Zscherpel, Uwe A1 - Griesche, Axel A1 - Kromm, Arne A1 - Hohendorf, Stephan A1 - Redmer, Bernard T1 - Real-time radiography for observation of crack growth during GTA (Gas Tungsten Arc) welding N2 - In situ crack detection in the mushy zone and the solid weld of a gas tungsten arc (GTA) weld using X-ray imaging during welding is a new research area for NDT inspection. Usually, NDT flaw detection is done after the complete solidification of the weld seam. In this paper, we present the use of real-time radiography with a minifocus X-ray source (YXLON X-ray tube Y.TU 225-D04) and a 75μm pixel size digital detector array (Dexela 1512) for the acquisition of 2D radiographic images by a sequence of exposures with time intervals of 80 ms for hot crack detection during single pass bead-on-plate GTA welding of 3 mm thick plates of aluminium alloy AlMgSi (6060). An analysis of the crack distribution in the weld sample is conducted from the acquired 2D radiographs and its corresponding 3D volumetric reconstruction achieved by linear coplanar digital laminography. This in situ approach opens new possibilities in the field of hot crack research by having the direct information of both the crack initiation and growth and its correlation to the welding parameters. KW - Hot cracking KW - Radiography KW - GTA welding KW - Aluminium alloys KW - Real-time operation PY - 2016 DO - https://doi.org/10.1007/s40194-016-0351-7 SN - 0043-2288 SN - 1878-6669 VL - 60 IS - 5 SP - 931 EP - 937 AN - OPUS4-37128 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -