TY - CONF A1 - Babutzka, Martin A1 - Lehmann, Jens A1 - Burkert, Andreas T1 - Stainless steels: Fundamentals and causes for corrosion defects N2 - The presentation gives an overview about the fundamentals on stainless steels. The mechanism of passive layer formation is explained and strategies for securing corrosion protection are given. The influence of a grinding process on corrosion resistance is discussed. T2 - Tech-Day Mettler Toledo CY - Online meeting DA - 23.11.2022 KW - Corrosion KW - Stainless steel KW - Grinding KW - KorroPad KW - Surface PY - 2022 AN - OPUS4-56370 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Dieck, S. A1 - Ecke, M. A1 - Rosemann, Paul A1 - Halle, T. T1 - Reversed austenite for enhancing ductility of martensitic stainless steel N2 - Quenching and partitioning (Q&P) heat Treatment increases the deformability of high-strength martensitic steels. Therefore, it is necessary to have some metastable austenite in the microstructure, which transforms in martensite during plastic deformation (TRIP effect). The austenitic-martensitic microstructure is gained by an increased austenitization temperature, water quenching and additional partitioning. The partitioning enables local carbon diffusion, which stabilizes retained austenite and leads to partial reversion of martensite to austenite. The influence of partitioning time was studied for the martensitic stainless steel AISI 420 (X46Cr13, 1.4034). In line with these efforts, metallographic, XRD and EBSD measurements were performed to characterize the microstructural evolution. The mechanical properties were tested using tension and compression loading. Additional corrosion investigations showed the benefits of Q&P heat treatment compared to conventional tempering. The reversion of austenite by the partitioning treatment was verified with EBSD and XRD. Furthermore, the results of the mechanical and corrosion testing showed improved properties due to the Q&P heat treatment. T2 - International Conference on Martensitic Transformations CY - Chicago, IL, USA DA - 09.07.2017 KW - Heat treatment KW - High ductility KW - Martensitic stainless steels KW - Quenching and partitioning KW - Transformation induced plasticity KW - KorroPad KW - EBSD KW - Mechanical testing PY - 2018 SN - 978-3-319-76968-4 U6 - https://doi.org/10.1007/978-3-319-76968-4_19 SP - 123 EP - 128 PB - Springer AN - OPUS4-44689 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kauss, N. A1 - Heyn, A. A1 - Rosemann, Paul T1 - How to Detect Sensitivity on Aged Lean-Duplex Stainless Steel With Electrochemical Methods N2 - The influence of isothermal ageing on microstructure, sensitisation and pitting corrosion resistance of the lean duplex stainless steel (LDSS) X2CrNiN23-4 was investigated with various electrochemical methods. The aging at 600 °C (from 0.1 h up to 20 h) lead to the formation of precipitations at the ferrite-ferrite (α/α) and ferrite-austenite (α/γ) grain boundaries, inducing sensitisation due to chromium depletion. The degree of sensitisation was evaluated with the double loop electrochemical potentiokinetic reactivation method (DL-EPR) according to ASTM G108 and correlated with critical pitting potentials (Epit) as well as critical pitting temperature (CPT) measured in an electrolyte according to ASTM G48 using electrochemical noise. Up to an ageing time of 1 h, the sensitisation did rise significantly, stabilising at a nearly constant level with a slight drop at 20 h. This behaviour correlated perfectly with the potentiodynamically determined pitting potentials Epit and sensitisation. The CPT showed a higher sensitivity at short ageing times compared to the DL-EPR and Epit. Finally, the KorroPad method was applied to visualise the sensitisation induced reduction of pitting corrosion resistance. The “KorroPad” is an agar-based gel-electrolyte containing 0.1 mol/l sodium chloride (NaCl) and 0.1 mol/l potassium ferricyanide III (K3[Fe(CN)6]), invented at the Federal Institute of Materials Research and Testing in Berlin (Germany) to detect surfaces of stainless steel prone to pitting corrosion. The standard configuration of the KorroPad showed no differentiation for the various aging conditions. Increasing the concentration of both NaCl and potassium ferrocyanide III to 0.5 M shifts the detection limit of the KorroPad method to stainless steels with higher corrosion resistance, producing the same trends detected by standard electrochemical pitting corrosion values (Epit, CPT) and sensitisation (DL-EPR). By that, the KorroPad method was successfully adjusted to the lean-duplex stainless steel X2CrNiN23-4, enabling short-time testing to detect sensitization. T2 - Electrochemical Methods in Corrosion Research 2018 CY - Cambridge, UK DA - 22.07.2018 KW - Corrosion testing KW - Duplex stainless steels KW - Corrosion KW - KorroPad KW - Pitting corrosion KW - EPR KW - Electrochemical noise KW - Stainless steel PY - 2018 AN - OPUS4-45615 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lehmann, Jens A1 - Leonhard, H. T1 - More certainty in corrosion prevention N2 - Protective passive coatings of stainless-steel piping systems and tanks in chemical plants are at risk – and not only from the harsh conditions prevalent during production operations. Even in new systems, defects can be caused by grinding or by incomplete removal of temper colours after welding. TÜV SÜD Chemie Service participated in the assessment of a rapid test for corrosion developed by the German Institute for Materials Research and Testing (Bundesanstalt für Materialforschung und -prüfung, BAM). In only 15 minutes, KorroPads deliver valid information about the condition of passive coatings on material surfaces. KW - Nichtrostender Stahl KW - Korrosionsschnelltest KW - KorroPad KW - Passivschicht PY - 2018 UR - http://digital.processingmagazine.com/July2018#&pageSet=11 SN - 0896-8659 VL - 31 IS - 07 SP - 20 EP - 21 PB - Endeavor Business Media CY - Birmingham, Alabama AN - OPUS4-45722 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lehmann, Jens A1 - Burkert, Andreas A1 - Mietz, Jürgen T1 - Investigations proofing the passive layer stability of stainless steels N2 - The presented investigations have proved the principal suitability of the KorroPad method to assess the passive layer stability of stainless steels. The electrochemical mode of action could be described in detail and limitations of the applicability have been demonstrated. The influence of different surface finishes has been investigated and verified by known methods for describing corrosion resistances. As a result, the increased corrosion susceptibility of two ground surfaces has been detected, but also the corrosion resistance of further surface finishes could be confirmed. KW - Stainless steel KW - KorroPad KW - Passive layer PY - 2016 U6 - https://doi.org/10.1002/maco.201408202 VL - 1 IS - 67 SP - 84 EP - 91 PB - WILEY-VCH Verlag GmbH & Co. KGaA CY - Weinheim AN - OPUS4-35545 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kauss, Norman A1 - Heyn, A. A1 - Halle, T. A1 - Rosemann, Paul T1 - Detection of sensitisation on aged lean duplex stainless steel with different electrochemical methods N2 - Ageing at 600 °C (from 0.1 h up to 20 h) leads to the formation of precipitations at the ferrite-ferrite (α/α) and ferrite-austenite (α/γ) grain boundaries of the lean duplex stainless steel (LDSS) X2CrNiN22-2. This leads to sensitisation due to chromium depletion and decreased pitting corrosion resistance proven by the results of various electrochemical methods (DL-EPR and determination of CPT, Epit). These results were compared with the KorroPad method, which uses an agar-based gel-electrolyte for the detection of stainless steel surfaces prone to pitting corrosion. However, the standard configuration of the KorroPad showed no differentiation for the various ageing conditions. Therefore, modified versions of the KorroPad with two, five and ten times higher NaCl and potassium ferrocyanide III (K3[Fe(CN)6]) concentrations were successfully used to visualise the behaviour detected by DL-EPR, Epit and CPT. Therefore, the KorroPad method can also detect a microstructure related reduction of pitting corrosion resistance, which can drastically reduce the experimental effort to generate sensitisation diagrams for stainless steels. KW - Lean duplex KW - Stainless steel KW - Sensitisation KW - Polarisation KW - Critical pitting temperature KW - Pitting corrosion KW - KorroPad KW - Ageing treatment PY - 2019 U6 - https://doi.org/10.1016/j.electacta.2019.05.081 SN - 0013-4686 SN - 1873-3859 VL - 317 SP - 17 EP - 24 PB - Elsevier AN - OPUS4-48374 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Dieck, S. A1 - Ecke, M. A1 - Rosemann, Paul A1 - Halle, T. T1 - Enhanced properties of martensitic stainless steel due to austenite reversion N2 - The novel heat treatment concept of “Quenching and Partitioning” (Q&P) enables producing low alloyed martensitic steels with high strength and formability. Therefore austenite, retaining from a quenching temperature between Mf and Ms, is stabilised by carbon diffusion. This stabilised austenite transforms in martensite (TRIP effect) under mechanical loading. Current investigations on the Q&P heat treatment of martensitic stainless steels reveal a further enhancement of mechanical properties due to higher amounts of austenite. Thus a tensile strength of 1.800 MPa and a maximum elongation of 20 % are possible, while mechanical properties under compression are much higher due to a distinct SD effect. The presentation aims to gain a further understanding of the Q&P heat treatment and the resulting mechanical properties for the steel X46Cr13, especially the mechanical behaviour under dynamic mechanical loading condition. Results of drop work and Split Hopkinson Pressure Bar test confirms the findings of quasi static compression test. Furthermore, Charpy impact tests show higher impact toughness compared to the common heat treatment of quenching and tempering (Q&T). Complementary investigations indicate a higher corrosion resistance of Q&P compared to Q&T. T2 - 12th International Nordmetall Colloquium CY - Chemnitz, Germany DA - 05.12.2017 KW - Corrosion resistance KW - Heat treatment KW - Martensite KW - Quenching and partitioning KW - Stainless steel KW - KorroPad PY - 2017 AN - OPUS4-43339 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rosemann, Paul A1 - Kauss, N. A1 - Müller, C. A1 - Halle, T. T1 - Heat treatment and corrosion resistance of cutlery N2 - Hardness and pitting corrosion resistance are the major quality criteria of cutlery. Both are achieved by the heat treatment (austenitization, quenching and tempering) of the normally used martensitic stainless steels. The established quality control method regarding the pitting corrosion resistance is an alternating immersion test in 1 % NaCl solution at 60 °C according to DIN EN ISO 8442. This standard test shows a high deviation, which limits any optimization of the heat treatment process. New approaches for corrosion testing of martensitic stainless-steels were developed and used in the last years to connect the weak pitting corrosion resistance of martensitic stainless-steels with the phenomenon of chromium depletion. The tempering temperatures used in the industrial heat treatment of cutlery are too low to explain the appearance of chromium depletion. For this reason, a systematic investigation of three heat treatment parameters (austenitization time, cooling speed and tempering temperature) were performed on the martensitic stainless-steels X50CrMoV15 (1.4116) to detect their contribution to chromium depletion. The electrochemical potentiodynamic reactivation (EPR), which is very sensitive to any change of the microstructure, was used to quantify the degree of chromium depletion. The KorroPad indicator-test was applied to correlate low pitting corrosion resistance to the presence of chromium depletion. The results of all investigations allow conclusions about the very small process window, which is necessary to achieve cutlery with high pitting corrosion resistance. T2 - EUROCORR 2018 CY - Krakow, Poland DA - 09.09.2018 KW - Corrosion KW - KorroPad KW - Stainless steel KW - Corrosion resistance KW - Heat treatment KW - EPR KW - Pitting corrosion KW - Martensitic stainless steels KW - REM PY - 2018 AN - OPUS4-45952 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rosemann, Paul A1 - Baumann, O. A1 - Müller, C. T1 - Influence of the post-weld surface treatment on the corrosion resistance of the duplex stainless steel 1.4062 N2 - The duplex stainless steel 1.4062 (X2CrNiN22-2) is used as alternative material to austenitic stainless steels in the construction industry. The corrosion resistance of welded seams is influenced by the base material, the weld filler material, the welding process and also by the final surface treatment. The scale layer next to the weld seam can be removed by grinding, pickling, electro-polishing or blasting depending on the requested corrosion resistance. Blasted surfaces are often used in the industrial practice due to the faster and cheaper manufacturing process compared to pickled or electro-polished surfaces. Furthermore blasting with corundum-grain is more effective than blasting with glass-beads which also lower the process costs. In recent years, stainless steel surfaces showed an unusually high susceptibility to pitting corrosion after grinding with corundum. For this reason, it is now also questioned critically whether the corrosion resistance is influenced by the applied blasting agent. This question was specifically investigated by comparing grinded, pickled, corundum-grain- and glass-bead-blasted welding seams. Results of the SEM analyses of the blasting agents and the blasted surfaces will be presented and correlated with the results of different corrosion tests (KorroPad-testing and pitting potentials). T2 - Materials Science and Engineering 2018 (MSE) CY - Darmstadt, Germany DA - 26.09.2018 KW - Duplexstahl KW - Korrosion KW - Nichtrostender Stahl KW - Schweißen KW - Oberflächenbearbeitung KW - Strahlen KW - KorroPad PY - 2018 AN - OPUS4-46090 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rosemann, Paul A1 - Müller, C. A1 - Roßberg, S. A1 - Pensel, P. A1 - Heyn, A. A1 - Burkert, Andreas T1 - Precipitation behavior and corrosion resistance of nickel-free, high-nitrogen austenitic stainless steels N2 - Nickel-free, nitrogen alloyed austenitic stainless-steels, with about 19 wt.-% Mn and 0,8 wt. % N, are an interesting alternative to classic CrNi austenitic stainless steels due to their superior mechanical properties (Rm > 900 MPa, A5 > 50 %, Av > 350 J) in the solution annealed condition. The formation of chromium-rich nitrides during suboptimal heat treatment, processing or application leads to an inhomogeneous distribution of alloying elements in the microstructure, which reduces the corrosion resistance. Consequently, an accurate knowledge of the sensitization behavior is indispensable for the use of nickel-free, high-nitrogen austenitic stainless steels. The relationship between artificial aging, phase formation and corrosion resistance was investigated on the alloys X8CrMnN18-19 (1.3815) and X8CrMnMoN18-19-2 (1.4456), both alloyed with 0,8 wt.-% Nitrogen, in the present work. The microstructural evolution was studied by LM and SEM while the corrosion resistance was characterized with the electrochemical potentiodynamic reactivation (EPR) and the KorroPad indicator-test. Both alloys showed increased corrosion susceptibility within critical aging parameters. Finally, a sensitization diagram was described successfully for both alloys showing the positive effect of molybdenum. T2 - Materials Science and Engineering 2018 (MSE) CY - Darmstadt, Germany DA - 26.09.2018 KW - Corrosion KW - Corrosion resistance KW - Heat treatment KW - KorroPad KW - Nitrogen KW - Pitting corrosion KW - Stainless steel KW - ThermoCalc PY - 2018 AN - OPUS4-46093 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Reinemann, Steffi A1 - Rosemann, P. A1 - Babutzka, Martin A1 - Lehmann, Jens A1 - Burkert, Andreas T1 - Influence of grinding parameters on the corrosion behavior of austenitic stainless steel N2 - Samples of the austenitic stainless steel grade X5CrNi18‐10 (1.4301, AISI 304) were ground industrially with various grinding parameters to study their influence on corrosion resistance. The ability of the mechanically ground surfaces to form a stable passive layer was evaluated by KorroPad test and a modified electrochemical potentiodynamic reactivation test based on a single loop (EPR‐SL). Furthermore, the surfaces were characterized by surface analytical methods. The main influence was determined regarding abrasive belt type. Surfaces mechanically ground with granulate abrasive belts constantly had a lower corrosion resistance than surfaces ground with single‐coated grain. The granulate abrasive belts generated more sensitized surface areas and left formations of welded sample material on the mechanically ground surfaces. A post‐treatment with a nonwoven abrasive proved to be an effective finishing process by which the surface defects and sensitized material got removed and the surfaces regained the expected corrosion resistance. KW - Abrasive belt KW - Austenitic stainless steel KW - Electrochemical potentiodynamic reactivation KW - Grinding KW - KorroPad KW - Surface KW - Corrosion PY - 2019 U6 - https://doi.org/10.1002/maco.201910874 SN - 0947-5117 SN - 1521-4176 VL - 70 IS - 10 SP - 1776 EP - 1787 PB - Wiley-VCH Verlag CY - Weinheim AN - OPUS4-47871 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -