13 Zentrale Universitätseinrichtungen
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Item Open Access Investigation of oxide layer development of X6CrNiNb18-10 stainless steel exposed to high-temperature water(2024) Veile, Georg; Hirpara, Radhika; Lackmann, Simon; Weihe, StefanThe oxide layer development of X6CrNiNb18-10 (AISI 347) during exposure to high-temperature water has been investigated. Stainless steels are known to form a dual oxide layer in corrosive environments. The secondary Fe-rich oxide layer has no significant protective effect. In contrast, the primary Cr-rich oxide layer is known to reach a stabilized state, protecting the base metal from further oxidation. This study’s purpose was to determine the development of oxide layer dimensions over exposure time using SEM, TEM and EDX line scans. While a parabolic development of Cr in the protective primary layer and Fe in the secondary layer was observed, the dimensions of the Ni layer remained constant. Ni required the presence of a pronounced Fe-rich secondary layer before being able to reside on the outer secondary layer. With increasing immersion time, the Ni element fraction surpassed the Cr element fraction in the secondary layer. Oxide growth on the secondary layer could be observed. After 480 h, nearly the entire surface was covered by the outer oxide layer. In the metal matrix, no depletion of Cr or Ni could be observed over time; however, an increased presence of Cr and Ni in the primary layer was found at the expense of Fe content. The Nb-stabilized stainless steel was subject to the formation of Niobium pentoxide (Nb2O5), with the quantity and magnitude of element fraction increasing over exposure time.Item Open Access Untersuchung der biologischen Wirkung polymerer Werkstoffe für Hohlfasern in Entsalzungsanlagen, die nach dem Prinzip der umgekehrten Osmose arbeiten(1980) Solochina, T. A.; Rachmanin, Ju. A.; Merkur'eva, R. V.; Saternikova, I. S.; Procenko, E. I.; Konstantinova, I. N.; Avchimenko, M. M.; Minceva, L. A.; Varsavskaja, S. P.; Vasjukovic, P. Ja.; Pertschi, Ottmar (Übersetzer)Biologische Wirkung von Polymeren mit umgekehrter Osmose in Entsalzungsanlagen.Item Open Access Methode zur Reinigung von Nickelchlorid(1989) Sidorov, N. S.; Kusaev, Ju. I.; Ulrich- von Oertzen, Andrea; Pertschi, Ottmarsiehe engl. ZusammenfassungItem Open Access Verfahren zur Erzeugung von Acylperoxiden : Patentbeschreibung zum Erfinder-Patent Nr. 498293 ... erteilt am 5.1.1976(1989) Ivanov, A. M.; Ivanova, L. A.; Pertschi, Ottmar (Übersetzer)Die Erfindung beschreibt das Verfahren zur Erzeugung von aromatischen und alkylaromatischen Acylperoxiden mit der gemeinsamen Formel ArC(O)OOC(O)R.Item Open Access Investigation of tool degradation during friction stir welding of hybrid aluminum-steel sheets in a combined butt and overlap joint(2024) Göbel, Robin; Schwertel, Stefanie; Weihe, Stefan; Werz, MartinFriction stir welding, as a solid-state welding technique, is especially suitable for effectively joining high-strength aluminum alloys, as well as for multi-material welds. This research investigates the friction stir welding of thin aluminum and steel sheets, an essential process in the production of hybrid tailor-welded blanks employed in deep drawing applications. Despite its proven advantages, the welding process exhibits variable outcomes concerning formability and joint strength when utilizing an H13 welding tool. To better understand these inconsistencies, multiple welds were performed in this study, joining 1 mm thick steel to 2 mm thick aluminum sheets, with a cumulative length of 7.65 m. The accumulation of material on the welding tool was documented through 3D scanning and weighing. The integrity of the resulting weld seam was analyzed through metallographic sections and X-ray imaging. It was found that the adhering material built up continuously around the tool pin over several welds totaling between 1.5 m and 2.5 m before ultimately detaching. This accretion of material notably affected the welding process, resulting in increased intermixing of steel particles within the aluminum matrix. This research provides detailed insights into the dynamics of friction stir welding in multi-material welds, particularly in the context of tool material interaction and its impact on weld quality.Item Open Access Investigations of metallurgical differences in AISI 347 and their influence on deformation and transformation behaviour and resulting fatigue life(2024) Veile, Georg; Regitz, Elen; Smaga, Marek; Weihe, Stefan; Beck, TillmannDue to variations in chemical composition and production processes, homonymous austenitic stainless steels can differ significantly regarding their initial microstructure, metastability, and thus, their fatigue behavior. Microstructural investigations and fatigue tests have been performed in order to evaluate this aspect. Three different batches and production forms of nominally one type of steel AISI 347 were investigated under monotonic tensile tests and cyclic loading under total strain and stress control in low and high cycle fatigue regimes, respectively. The deformation induced α’-martensite formation was investigated globally by means of in situ magnetic measurements and locally using optical light microscopy of color etching of micrographs. The investigation showed that the chemical composition and the different production processes influence the material behavior. In fatigue tests, a higher metastability and thus a higher level of deformation induced α’-martensite pronounced cyclic hardening, resulting in significantly greater endurable stresses in total strain-controlled tests and an increase in fatigue life in stress-controlled tests. For applications of non-destructive-testing, detailed knowledge of a component’s metastability is required. In less metastable batches and for lower stress levels, α’-martensite primarily formed at the plasticization zone of a crack. Furthermore, the formation and nucleation points of α’-martensite were highly dependent on grain size and the presence of δ-ferrite. This study provides valuable insights into the different material behavior of three different batches with the same designation, i.e., AISI 347, due to different manufacturing processes and differences in the chemical composition, metastability, and microstructure.Item Open Access Über die hygienische Bewertung von entsalztem Wasser, das durch umgekehrte Osmose in "Filter-Presse"-Anlagen gewonnen wurde(1980) Selivanov, S. B.; Pertschi, Ottmar (Übersetzer)Ständige Wassergüteprüfung von Zellulose-Acetat-Membranen bei der Entsalzung durch umgekehrte Osmose.Item Open Access Microstructure-based lifetime assessment of austenitic steel AISI 347 in view of fatigue, environmental conditions and NDT(2021) Acosta, Ruth; Heckmann, Klaus; Sievers, Jürgen; Schopf, Tim; Bill, Tobias; Starke, Peter; Donnerbauer, Kai; Lücker, Lukas; Walther, Frank; Boller, ChristianThe assessment of metallic materials used in power plants’ piping represents a big challenge due to the thermal transients and the environmental conditions to which they are exposed. At present, a lack of information related to degradation mechanisms in structures and materials is covered by safety factors in its design, and in some cases, the replacement of components is prescribed after a determined period of time without knowledge of the true degree of degradation. In the collaborative project “Microstructure-based assessment of maximum service life of nuclear materials and components exposed to corrosion and fatigue (MibaLeb)”, a methodology for the assessment of materials’ degradation is being developed, which combines the use of NDT techniques for materials characterization, an optimized fatigue lifetime analysis using short time evaluation procedures (STEPs) and numerical simulations. In this investigation, the AISI 347 (X6CrNiNb18-10) is being analyzed at different conditions in order to validate the methodology. Besides microstructural analysis, tensile and fatigue tests, all to characterize the material, a pressurized hot water pipe exposed to a series of flow conditions will be evaluated in terms of full-scale testing as well as prognostic evaluation, where the latter will be based on the materials’ data generated, which should prognose changes in the material’s condition, specifically in a pre-cracked stage. This paper provides an overview of the program, while the more material’s related aspects are presented in the subsequent paper.