TY - JOUR A1 - Taparli, Ugur Alp A1 - Kannengießer, Thomas A1 - Cieslik, K. A1 - Mory, D. A1 - Griesche, Axel T1 - In situ chemical composition analysis of a tungsten-inert-gas austenitic stainless steel weld measured by laser-induced breakdown spectroscopy N2 - The chemical composition of a weld metal determines the resulting solidification mode of stainless steel and the consequent weld metal quality. In this work tungsten inert gas (TIG) welding of EN grade 1.4435 austenitic stainless steel was monitored using laser-induced breakdown spectroscopy (LIBS) for the in situ measurement of chemical composition changes. This research aims to prototype a real-time chemical composition analysis system for welding applications and prove the feasibility of such quality control loop. LIBS was used to investigate in situ the monitoring of metal vaporization during TIG welding. We found Mn vapor formation above the weld pool and subsequent condensation of Mn on the weld metal surface using LIBS. Post-weld line scans were conducted by LIBS on various welds produced with different welding currents. Local changes of Ni and Mn were observed at higher welding currents. The results are in good agreement with the literature and proved that LIBS can be used in situ to inspect the TIG welding process. T2 - 10th Euro-Mediterranean Symposium on Laser-Induced Breakdown Spectroscopy CY - Brünn, Czechia DA - 08.09.2019 KW - LIBS KW - Welding KW - Austenitic stainless steel KW - Metal vapor KW - In situ measurement PY - 2020 DO - https://doi.org/10.1016/j.sab.2020.105826 SN - 0584-8547 VL - 167 SP - 105826 PB - Elsevier B.V. CY - Amsterdam, Niederlande AN - OPUS4-50582 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pfretzschner, Beate A1 - Schaupp, Thomas A1 - Griesche, Axel T1 - Hydrogen in Metals Visualized by Neutron Imaging N2 - Neutron cameras allow visualizing hydrogen distributions with radiographic or tomographic imaging methods in iron (and steel) and many other metals. The necessary contrast between hydrogen and these metals stems from the high difference in the total neutron cross section of both elements. This allows, e.g., the in situ measurement of hydrogen mass flow inside cm thick metal samples with a temporal resolution of at best 10 s using neutron radiography as well as the quantitative measurement of hydrogen accumulations, e.g., at the crack’s inner surfaces in hydrogen embrittled iron samples with neutron tomography. This new quality of the information on a micrometer scale allows new insights for the analysis of hydrogen-assisted damage mechanisms. Further, this method is non-destructive and provides local information in situ and in three dimensions with a spatial resolution of 20 μm - 30 μm. In this contribution, we give a short historical overview of neutron imaging and show examples that demonstrate the spatial and temporal resolution of the neutron radiography and tomography methods in order to visualize and quantify hydrogen accumulations, absorption processes, and diffusion. The examples are taken from the works of researchers dealing with titanium, palladium, zirconium, and iron or steel. More detailed descriptions of the experimental and analytic procedures are given for hydrogen detection using radiography and tomography on iron and steel samples. KW - Hydrogen assisted cracking KW - Neutron imaging PY - 2019 DO - https://doi.org/10.5006/3104 SN - 0010-9312 VL - 75 IS - 8 SP - 903 EP - 910 PB - NACE International AN - OPUS4-48775 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Konadu, D. S. A1 - Pistorius, P. G. H. A1 - Du Toit, M. A1 - Griesche, Axel T1 - Solidification cracking susceptibility of ferritic stainless steels using Modified Varestraint Transvarestraint (MVT) method N2 - The Modified Varestraint Transvarestraint (MVT) test was used to investigate the solidification cracking susceptibility of an unstabilised, a Nb-stabilised and two (Ti + Nb) dual-stabilised ferritic stainless steels. Two different welding speeds of 6 and 3 mm/s using autogenous gas tungsten arc welding were employed. At the welding speed of 6 mm/s, the high-content (Ti + Nb) steel was resistant and the Nb-stabilised steel was marginally susceptible to solidification cracking. At the welding speed of 3 mm/s, the Nb and the high (Ti + Nb) steels were found to be marginally susceptible to solidification cracking while the unstabilised and low-content (Ti + Nb) grades were resistant to solidification cracking. The weld metal microstructures transverse to the welding direction revealed columnar grains in all the samples for both welding speeds. The ferritic stainless steels were generally resistant to solidification cracking, except the Nb-stabilised steel, which was marginally susceptible to solidification cracking. KW - Susceptibility KW - Modified Varestraint Transvarestraint KW - Solidification cracking KW - Ferritic stainless steel KW - Microstructure KW - Welding PY - 2019 DO - https://doi.org/10.1007/s12046-019-1175-0 SN - 0973-7677 VL - 44 IS - 9 SP - Article Number: UNSP 194 PB - Springer AN - OPUS4-48938 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 - CHAP A1 - Browne, D. A1 - García-Moreno, F. A1 - Nguyen-Thi, H. A1 - Zimmermann, G. A1 - Kargl, F. A1 - Mathiesen, R. H. A1 - Griesche, Axel A1 - Minster, O. ED - Solanki, K. N. ED - Orlov, D. ED - Singh, A. ED - Neelameggham, N. R. T1 - Overview of In situ X-ray studies of light alloy solidification in microgravity N2 - Gravity has significant effects on alloy solidification, primarily due to thermosolutal convection and solid phase buoyancy. Since 2004, the European Space Agency has been supporting investigation of these effects by promoting in situ X-ray monitoring of the solidification of aluminium alloys on microgravity platforms, on earth, and in periodically varying g conditions. The first microgravity experiment-investigating foaming of liquid metals - was performed on board a sounding rocket, in 2008. In 2012 the first ever X-ray-monitored solidification of a fully dense metallic alloy in space was achieved: the focus was columnar solidification of an Al-Cu alloy. This was followed in 2015 by a similar experiment, investigating equiaxed solidification. Ground reference experiments were completed in all cases. In addition, experiments have been performed on board parabolic flights-where the effects of varying gravity have been studied. We review here the technical and scientific progress to date, and outline future perspectives. KW - Dendritic growth KW - Materials in space KW - Columnar and equiaxed structures PY - 2017 SN - 978-3-319-52392-7 SN - 978-3-319-52391-0 DO - https://doi.org/10.1007/978-3-319-52392-7_80 SN - 2367-1181 SP - 581 EP - 590 PB - Springer CY - Berlin, Heidelberg AN - OPUS4-39442 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Serrano Munoz, Itziar A1 - Pfretzschner, Beate A1 - Kromm, Arne A1 - Nadammal, Naresh A1 - Kardjilov, N. A1 - Markötter, Henning A1 - Neuwirth, T. A1 - Schulz, M. A1 - Griesche, Axel T1 - High-resolution Bragg-edge neutron radiography detects grain morphology in PBF-LB/M IN718 N2 - One of the main advantages of metal additive manufacturing (MAM) techniques is their ability to produce components with site-specific microstructural features. Nevertheless, microstructural defects and lack of repeatability are still major concerns in MAM. In this study, a laser powder bed fusion (PBF-LB/M) IN718 material, produced using two different scan length vectors, is investigated using Bragg-edge neutron 2D imaging (BENI) combined with electron backscatter diffraction (EBSD) analysis. BENI is able to detect, on a macroscopic scale, process-induced changes in texture in a large field of view covering the entire sample (20×80 mm2). In addition, high-resolution BENI (HR-BENI), with a pixel size of 12.8 µm, provides a micro-scale examination of the local variations of texture and grain morphology, otherwise undistinguishable using the standard resolution. As such, HR-BENI offers a straightforward and detailed way of screening the integrity of MAM parts at cm-length scales. KW - Bragg-edge neutron 2D imaging (BENI) KW - Metal additive manufacturing (MAM) KW - IN718 PBF-LB/M KW - Crystallographic texture control KW - Electron backscatter diffraction (EBSD) PY - 2023 DO - https://doi.org/10.1016/j.mtla.2023.101827 SN - 2589-1529 VL - 30 SP - 1 EP - 6 PB - Elsevier CY - Amsterdam AN - OPUS4-57819 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 -