@misc{WeissSchnauberFischer, author = {Weiß, Sabine and Schnauber, T. and Fischer, Annette}, title = {Microstructure Characterization of thin structures after deformation}, series = {Materials and devices for smart systems III, symposium held December 1 - 4, 2008, Boston, Massachusetts}, journal = {Materials and devices for smart systems III, symposium held December 1 - 4, 2008, Boston, Massachusetts}, editor = {Su, Ji}, publisher = {MRS}, address = {Warrendale, Pa.}, isbn = {978-1-605-11101-8}, pages = {V11 -- 19}, language = {en} } @misc{AmerWeissFischer, author = {Amer, A. E. and Weiß, Sabine and Fischer, Annette}, title = {Improvement of fatigue resistance of low-nickel stainless steels for biomedical applications compared to CoCr-alloys}, series = {Steel grips}, volume = {7}, journal = {Steel grips}, number = {6}, issn = {1866-8453}, pages = {457 -- 461}, language = {en} } @misc{WeissSzymczakMeissner, author = {Weiß, Sabine and Szymczak, H. and Meissner, Andreas}, title = {Fatigue and endurance of coronary stents}, series = {Materialwissenschaft und Werkstofftechnik}, volume = {40}, journal = {Materialwissenschaft und Werkstofftechnik}, number = {1-2}, issn = {1521-4052}, pages = {61 -- 64}, language = {en} } @misc{GarkasWeissWang, author = {Garkas, Wagdi and Weiß, Sabine and Wang, Q. M.}, title = {(Cr1-x Al x)N as a candidate for corrosion protection in high temperature segments of CCS plants}, series = {Environmental Earth Sciences}, journal = {Environmental Earth Sciences}, issn = {1866-6280}, doi = {10.1007/s12665-013-2646-y}, abstract = {Three (Cr1-x Al x )N (x = 0.33, 0.5, 0.66) coatings were deposited on Ni-super alloy IN718 using reactive magnetron sputtering. The oxidation behavior of all coatings at 900 °C up to 500 h in air was studied. Furthermore, the corrosion behavior of the (Cr0.33,Al0.66)N coating at 900 °C (corrosion type I) by spraying a uniform salt scale of Na2SO4 on the sample surface (1 mg/cm2) was investigated. It was found that the coated samples indicate significantly higher oxidation and corrosion resistance compared to uncoated Ni super alloy. This is mainly due to the formation of protective Cr2O3 and Al2O3 layers on the coating surface. With the increase of Al content, the coatings exhibited improved oxidation resistance. The formation of thin and adherent Al2O3 scale on the surface of Al rich coating is the reason for its better oxidation behavior. The detailed structures of the oxide scales and the interdiffusion between coating and substrate were studied using energy dispersive X-ray spectroscopy-analysis.}, language = {en} } @inproceedings{WeissMeissner, author = {Weiß, Sabine and Meissner, Andreas}, title = {Austenitic high nitrogen steel: An alternative material for coronary stents?}, series = {8th World Biomaterials Congress 2008, Amsterdam, 28 May - 1 June 2008}, booktitle = {8th World Biomaterials Congress 2008, Amsterdam, 28 May - 1 June 2008}, publisher = {Curran Associates Inc.}, address = {Red Hook, NY}, isbn = {978-1-61567-080-2}, language = {en} } @misc{FischerBurgaudAmeretal., author = {Fischer, Annette and Burgaud, D. and Amer, A. E. and Weiß, Sabine}, title = {Fatigue aspects of the generation of nanoparticles during wear of biomedical alloys}, series = {8th World Biomaterials Congress 2008, Amsterdam, 28 May - 1 June 2008}, journal = {8th World Biomaterials Congress 2008, Amsterdam, 28 May - 1 June 2008}, publisher = {Curran Associates Inc.}, address = {Red Hook, NY}, isbn = {978-1-61567-080-2}, language = {en} } @misc{KazakWeiss, author = {Kazak, Fedor and Weiß, Sabine}, title = {Analysis of the Frequency as an Integral Method for the Testing of Anisotropic 3D Sheet Metal Structure}, series = {Materials Testing}, volume = {56}, journal = {Materials Testing}, number = {9}, issn = {0025-5300}, pages = {656 -- 661}, language = {en} } @misc{RanjbarnodehWeissHankeetal., author = {Ranjbarnodeh, Eslam and Weiß, Sabine and Hanke, Stefanie and Fischer, Alfons}, title = {EBSD characterization of the effect of welding parameters on HAZ of AlSl409}, series = {Journal of Mining and Metallurgy : B, Metallurgy}, volume = {48}, journal = {Journal of Mining and Metallurgy : B, Metallurgy}, number = {1}, pages = {115 -- 121}, language = {en} } @misc{RanjbarnodehHankeWeissetal., author = {Ranjbarnodeh, Eslam and Hanke, Stefanie and Weiß, Sabine and Fischer, Alfons}, title = {Effect of welding parameters on the heataffected zone of AlSI409 ferritic stainless steel}, series = {International Journal of Minerals, Metallurgy and Materials}, volume = {19}, journal = {International Journal of Minerals, Metallurgy and Materials}, number = {10}, issn = {1869-103X}, pages = {923 -- 929}, language = {en} } @misc{FischerMeissnerWeiss, author = {Fischer, Annette and Meissner, Andreas and Weiß, Sabine}, title = {Microstructural peculiarities and mechanical properties of coronary stents}, series = {Nonlocal Modelling of Failure of Materials, proceedings of an international workshop, University of Wuppertal, June 2007}, journal = {Nonlocal Modelling of Failure of Materials, proceedings of an international workshop, University of Wuppertal, June 2007}, editor = {Yuan, Huang and Wittmann, Folker H.}, publisher = {Aedificatio Publ.}, address = {Freiburg}, isbn = {978-3-931681-87-6}, pages = {91 -- 104}, language = {en} } @phdthesis{Weiss, author = {Weiß, Sabine}, title = {Mikrostruktur- und Mikrotexturentwicklung bei der zyklischen Hochtemperaturverformung reiner kubisch-fl{\"a}chenzentrierter Metalle}, publisher = {Shaker}, address = {Aachen}, isbn = {3-8265-3372-0}, pages = {IV, 152}, language = {de} } @misc{HeringKailEckertetal., author = {Hering, Daniel and Kail, Jochem and Eckert, Sabine and Gerhard, Marc and Meyer, Elisabeth I. and Mutz, Michael and Reich, Michael and Weiss, Ilga}, title = {Coarse Woody Debris Quantity and Distribution in Central European Streams}, series = {International Review of Hydrobiology}, volume = {85}, journal = {International Review of Hydrobiology}, number = {1}, issn = {1522-2632}, doi = {10.1002/(SICI)1522-2632(200003)85:1<5::AID-IROH5>3.0.CO;2-X}, pages = {5 -- 23}, language = {en} } @misc{BolzOehringLindemannetal., author = {Bolz, Sebastian and Oehring, Michael and Lindemann, Janny and Pyczak, Florian and Paul, Jonathan and Stark, Andreas and Lippmann, Thomas and Roth-Fagaraseanu, Dan and Schreyer, Andreas and Weiß, Sabine and Schr{\"u}fer, Susanne}, title = {Microstructure and mechanical properties of a forged beta-solidifying gamma TiAl alloy in different heat treatment conditions}, series = {Intermetallics}, volume = {2015}, journal = {Intermetallics}, number = {58}, pages = {71 -- 83}, language = {en} } @misc{SchulzeSeidlitzKoenigetal., author = {Schulze, Marcus and Seidlitz, Holger and K{\"o}nig, Franziska and Weiß, Sabine}, title = {Tribological Investigations of PVD Coated Multi-Layer Constructions}, series = {Journal of Materials Science Research}, volume = {5}, journal = {Journal of Materials Science Research}, number = {1}, issn = {1927-0585}, doi = {10.5539/jmsr.v5n1p97}, pages = {97 -- 106}, abstract = {Multi-layer constructions become more and more relevant in lightweight applications due to their high strength to weight ratio. They offer excellent crash, damping and recycling properties. Also, the morphology of thermoplastic carbon fibre reinforced plastics (CFRP) render them interesting for large scale manufacturing processes. Nevertheless, a major disadvantage results in a poor resistance against wear and tear, e.g. erosion, which is attributed to weak hardness properties. Hence, this work deals with tribological investigations on orthotropic carbon fibre reinforced polymers (PA 6) either with protective ceramic coating or without. The chosen coating system is a well-known protective covering of metal components, e.g. metal cutting tools, produced by physical vapor deposition (PVD). To characterize the coating system on thermoplastic CFRP, standard analyzing methods are utilized, like optical and scanning electron microscopy (SEM). The tribological investigations are conducted by the tribological ball on disk method to generate wear tracks on the sample surfaces and hence to calculate the wear rates. These results are compared to literature findings with respect to a certain protective coating system (TiN) and a second nano-structured gel coating system, where both systems are deposited on a thermosetting material, i.e. carbon fibre reinforced epoxy resin, respectively. For this purpose the feasibility of depositing a protective ceramic layer on thermoplastic CFRP is demonstrated. First results on suitable surface pre-treatments have shown a significant influence on the coating quality. The improved performance regarding the wear behavior with respect to tribology compared to the poor substrate and existing technologies is shown additionally.}, language = {en} } @misc{OehringLindemannPyczaketal., author = {Oehring, Michael and Lindemann, Janny and Pyczak, Florian and Paul, Jonathan and Stark, Andreas and Lippmann, Thomas and Schr{\"u}fer, Susanne and Roth-Fagaraseanu, Dan and Schreyer, Andreas and Weiß, Sabine}, title = {Microstructure and mechanical properties of a forged β-solidifying γ TiAl alloy in different heat treatment conditions}, series = {Intermetallics}, volume = {2015}, journal = {Intermetallics}, number = {58}, issn = {0966-9795}, doi = {10.1016/j.intermet.2014.11.008}, pages = {71 -- 83}, abstract = {In the cast condition g titanium aluminide alloys that solidify completely through the b phase are characterized by fine and homogeneous microstructures, weak textures and low segregation. For these reasons such alloys have a relatively good workability and can be closed-die forged without preceding ingot breakdown even if the alloys contain no large fractions of the b phase at the working temperature. The present work was devoted to a combined study of the constitution and microstructural morphologies that develop in various two-step heat treatments of a single-step forged b solidifying alloy. The study included high-energy X-ray diffraction for in situ investigations of the constitution at the heat treatment temperature. It was observed that the phase ransformations are quite sluggish in the material which results in fine microstructures and some conditions that significantly deviate from thermodynamic equilibrium. Further, tensile and creep testing was carried out on the different material conditions in order to identify the range in which the properties can be varied. It is found that this easily forgeable material exhibits comparable strength, ductility and creep strength as more conventional peritectically solidifying alloys.}, language = {en} } @misc{KazakWeiss, author = {Kazak, Fedor and Weiß, Sabine}, title = {Test procedure for fatigue investigations regarding structured sheet metal joints}, series = {Materials Testing}, volume = {58}, journal = {Materials Testing}, number = {2}, issn = {0025-5300}, pages = {109 -- 116}, abstract = {The topic of fatigue strength of joints of flat and honeycomb-structured thin sheets has not yet been adequately studied. This concerns, for example,the development of an appropriate test method. In many cases, there is still a lack of information, how effective joints of flat and structured sheet metals are in omparison with reference joints of flat sheets. Combinations of resistance spot-welded specimens of flat and honeycomb-structured thin sheets of deep-drawing steel DC04 with a thickness of 0.5 mm were examined. Adopted clamping plates were applied for the testing. Joined smooth specimens were used as a reference material. The analysis of the frequency [1] was applied for comparison. The fatigue limit of a joint of a flat and a structured sheet metal is not significantly affected by spot welding. The fatigue limit of these spot-welded joints is comparable to that of an non joined honeycomb-structured sheet. By means of frequency or stiffness analysis, stability and damage mechanisms of differently shaped joints were explained. The joining of bridges of the structure shows a better stability than the combination of honeycombs. The stiffness analysis is a favored method for the clarification of the damage mechanisms in a spot-welded joint. The reasons for the low fatigue strength values of the joined flat-structured specimens compared to flat-flat joints are strong notch effects in the bridge area and momentum effects by the structure height of the studied honeycomb structure. The spot weld with a pronounced indentation also affected the fatigue strength of both flat and structured joined sheet metals.}, language = {en} } @misc{KazakWeiss, author = {Kazak, Fedor and Weiß, Sabine}, title = {Comparability of structured and flat reference specimens made of thin sheet metal}, series = {Materials Testing}, volume = {57}, journal = {Materials Testing}, number = {6}, issn = {0025-5300}, doi = {10.3139/120.110748}, pages = {567 -- 573}, abstract = {The literature review reveals that the honeycomb-structured thin sheet metals are not adequately investigated with regard to their fatigue strength. A question that remains almost completely ignored in the process is the direct comparability of structured thin sheet metals with flat reference specimens. A thin sheet is not a classic specimen to determine the fatigue strength because of the known problem of the fracture mechanics. Structured thin sheet metals of deep-drawing steel DC04 with a thickness of 0.5 mm were examined. Flat specimens were used as reference material. The frequency analysis was used for comparison. Fundamental differences in the mechanical behavior between flat and structured sheets under cyclic load were observed. Whereas an extremely flat S-N curve in the low-cycle region with a high slope coefficient was observed for the smooth thin sheets, the structured specimens show a curve typical for notched specimens. Moreover, the smooth sheets have a specific cyclic hardening and/or softening behavior. The state of plane stress of a fine sheet in contrast to a multi-axial one for the structured sheet complicates the direct comparison. For this reason, such a comparison with respect to their fatigue strength in the Wohler diagram should only be considered with caution.}, language = {en} } @misc{WeissMitevski, author = {Weiß, Sabine and Mitevski, Bojan}, title = {Microstructure and Deformation of Coronary Stents from CoCr-Alloys with Different Designs}, series = {Materials}, volume = {8}, journal = {Materials}, number = {5}, issn = {1996-1944}, doi = {10.3390/ma8052467}, pages = {2467 -- 2479}, abstract = {Coronary heart disease is still one of the most common sources for death in western industrial countries. Since 1986, a metal vessel scaffold (stent) has been inserted to prevent the vessel wall from collapsing. Most of these coronary stents are made from CrNiMo­steel (316L). Due to its austenitic structure, the material shows a good combination of strength, ductility, corrosion resistance, and biocompatibility. However, this material has some disadvantages like its non-MRI compatibility and its poor fluoroscopic visibility. Other typically used materials are the Co­Base alloys L-605 and F-562 which are MRI compatible as well as radiopaque. Another interesting fact is their excellent radial strength and therefore the ability to produce extra thin struts with increased strength. However, because of a strut diameter much less than 100 μm, the cross section consists of about 5 to 10 crystal grains (oligo­crystalline). Thus, very few or even just one grain can be responsible for the success or failure of the whole stent. To investigate the relation between microstructure, mechanical factors and stent design, commercially available Cobalt-Chromium stents were investigated with focus on distinct inhomogeneous plastic deformation due to crimping and dilation. A characteristic, material related deformation behavior with predominantly primary slip was identified to be responsible for the special properties of CoCr stents.}, language = {en} } @misc{NaveedFloresRenteriaNebeletal., author = {Naveed, Muhammad and Flores Renteria, Arturo and Nebel, Daniel and Weiß, Sabine}, title = {Study of high velocity solid particle erosion behaviour of Ti2AlC MAX phase coatings}, series = {Wear}, volume = {2015}, journal = {Wear}, number = {342-343}, issn = {0043-1648}, doi = {10.1016/j.wear.2015.09.014}, pages = {391 -- 397}, abstract = {This research work provides information about the influence of Ti2AlC MAX phase coatings on the erosion resistance of Ti624 2alloy.Flat specimens were coated witha20 µm Ti2AlC film using an industrial siz emagnetron sputtering coater and annealed at 800 °C for 1h in vacuum for the formation of the MAX phase.The erosion resistance of the specimens was tested using high velocity particles at room temperature.The results indicate that the erosion resistance of Ti6242 has been significantly enhanced by the employment of MAX-phase coatings. This demonstrates the capability of using MAX phase coatings as erosion protective medium for engine components exposed to similar damage conditions. Additionally,the results show that uncoated Ti6242 samples with duplex microstructure have a better durability against erosion attack compared to uncoated samples with globular microstructure.}, language = {en} } @misc{NaveedObrosovWeiss, author = {Naveed, Muhammad and Obrosov, Aleksei and Weiß, Sabine}, title = {Investigation of the wear resistance properties of Cr/CrN multilayer coatings against sand erosion}, series = {Conference Papers in Science}, volume = {2015}, journal = {Conference Papers in Science}, doi = {10.1155/2015/873543}, pages = {1 -- 10}, abstract = {The wear of metallic components used in gas and steam turbines due to erosive sand particles lead to a tremendous decrease in their lifetime. This wear can be reduced by the use of suitable erosion resistant coatings resulting in lower maintenance costs. In this context, multilayer Cr/CrN PVD coatings using an industrial coater was designed and applied on Inconel 718, a material which finds its application in gas turbines. A variation in the bimodal period has been induced in order to achieve an optimal coating architecture providing optimum properties needed for the erosion resistant coatings. The coating was deposited using a single Cr- target with an induction of N2 during the nitriding phase at a temperature of 480-500 °C and the coating thickness of 24-26 µm was kept constant throughout. The erosion tests were conducted at angles of 30°, 60° and 90°. The sand used for the test is an irregular shaped SiO2. The erosion tests were followed by a detailed microscopic examination of the eroded coating structure in combination with nanoindentation and scratch tests.}, language = {en} } @incollection{MlikotaSchmauderMitevskietal., author = {Mlikota, Marjo and Schmauder, Siegfried and Mitevski, Bojan and Weiß, Sabine}, title = {Scientific Multiscale and Multidisciplinary Analysis of Deformation and Damage in the Case of Oligocrystalline Structures}, series = {Computer Science and Engineering Technology}, booktitle = {Computer Science and Engineering Technology}, editor = {Deng, Jiamei and Liu, Quingjun}, publisher = {World Scientific Publishing}, address = {Singapore}, isbn = {978-981-4651-00-4}, pages = {113 -- 118}, abstract = {This paper serves as an overview of the ongoing research in the field of multiscale and multidisciplinary analysis of deformation and damage in the case of oligocrystalline structures. The research focuses on experimental measurement and numerical calculation of ductile failure in the X2CrNiMo18-15-3 (AISI 316L) stainless steel. An embedding numerical technique is employed where crystal plasticity theory is used to represent plastic deformation in the material and element removal technique based on Rice\&Tracey damage model for ductile void growth to simulate damage initiation inside the material, which is observed in the experiments. Additionally, the crystal plasticity model is supported by a hierarchical multiscale approach connecting nano-, micro- and meso-scales.}, language = {en} } @misc{SchulzeSeidlitzKoenigetal., author = {Schulze, Marcus and Seidlitz, Holger and K{\"o}nig, Franziska and Weiß, Sabine}, title = {Nanoindentation measurements of PVD coated multilayer constructions}, series = {Journal of Achievements in Materials and Manufacturing Engineering}, volume = {72}, journal = {Journal of Achievements in Materials and Manufacturing Engineering}, number = {2}, issn = {1734-8412}, pages = {53 -- 60}, abstract = {Carbon fibre reinforced thermoplastics (CFRP) are intensively used in lightweight applications due to their high strength to weight ratio. In addition they offer good crash, damping and recycling properties. On the basis of their morphology they are suitable for large scale manufacturing processes. A major disadvantage consists of its poor hardness properties, which is again an important requirement to realize a good erosion and wear behaviour. Design/methodology/approach: In this work the application of orthotropic carbon fibre reinforced polymers (PA6), with protective TiAlN coatings, produced by physical vapor deposition (PVD), is investigated. The characterization of the coating is performed by nanoindentation tests, roughness measurements and scanning electron microscopy. Furthermore micro hardness tests on selected well prepared cross sections are conducted, to compare the coating quality with established coating systems. Findings: By applying TiAlN coating, the hardness of the CFRP samples can be increased substantially up to 15 GPa, in comparison to the basic substrate. In addition the quality of the coating surface can be improved significantly by plasma etching pre-treatment. Research limitations/implications: The presented findings are preliminary results to prove the application of a standard processed ceramic coating on new composite types for mass production. The PVD coating process as well as the utilized testing methods are suitable to realize hard coatings on thermoplastic CFRP. This effect can be exploited for several lightweight applications to increase the erosion and wear resistance of composite materials. Originality/value: The presented results show, that ceramic coatings can be deposited on standard thermoplastic CFRP with polyamide 6 matrix. Therewith it can be expected, that the PVD coating process can make a essential contribution to increase the range of applications.}, language = {en} } @misc{SchulzeSeidlitzKoenigetal., author = {Schulze, Marcus and Seidlitz, Holger and K{\"o}nig, Franziska and Weiß, Sabine}, title = {Highly wear resistant PVD coatings for CFRP based multi-layer construction}, series = {11th International Scientific-Technical Conference on Advances in Plastics Technology (APT'15)}, journal = {11th International Scientific-Technical Conference on Advances in Plastics Technology (APT'15)}, address = {Gliwice}, isbn = {978-83-63555-47-4}, language = {en} } @misc{StechowIvanovaNaveedetal., author = {Stechow, Richard and Ivanova, Irina and Naveed, Muhammad and Weiß, Sabine}, title = {Sample Preparation of Worn Surfaces for EBSD Analysis}, series = {Praktische Metallographie}, volume = {53}, journal = {Praktische Metallographie}, number = {6}, issn = {0032-678x}, doi = {10.3139/147.110401}, pages = {352 -- 359}, language = {en} } @misc{NaveedStechowBolzetal., author = {Naveed, Muhammad and Stechow, Richard and Bolz, Sebastian and Hobusch, Katharina and Weiß, Sabine}, title = {Solid Particle Erosion of Heat Treated TNB-V4 at Ambient and Elevated Temperatures}, series = {International Journal of Chemical, Molecular, Nuclear, Materials and Metallurgical Engineering}, volume = {10}, journal = {International Journal of Chemical, Molecular, Nuclear, Materials and Metallurgical Engineering}, number = {5}, pages = {571 -- 576}, language = {en} } @misc{KazakSchleussOssenbrinketal., author = {Kazak, Fedor and Schleuß, Leander and Ossenbrink, Ralf and Michailov, Vesselin and Weiß, Sabine}, title = {Particularities of testing structured sheet metals in 3-point bending tests}, series = {Materials Testing}, volume = {58}, journal = {Materials Testing}, number = {6}, issn = {0025-5300}, doi = {10.3139/120.110883}, pages = {495 -- 500}, abstract = {Thin sheet metals from deep drawing steel DC04 are very often used in the production of car body and case parts. Quality improvement of sheet metal components by new constructive solutions (structuring) as well as adapted joining technology is going on. Structured sheet metals differ from each other by their high bending stiffness. At the same time, they show certain anisotropy due to the structure. Therefore a typical testing method of structured semi-finished parts (single sheet metals, sandwiches)is the bending test. The literature review revealed that in many studies no special demands on tests of structured materials were made. This concerns particularly the structure arrangement, structure direction and structure location of the specimen relative to the mandrel position during bending tests, i. e., the direction of the fixed load relative to the structure. The aim of this study was to determine the influence of the test specification on flexural behavior. In the present paper, honeycomb-structured sheet metals were examined using 3-point bending tests. Bending stiffness and lightweight potential were calculated with respect to the location of load application and compared for different structure arrangements,directions and locations. The influence of the anisotropy on flexural behavior of the honeycomb-patterned sheet metals was moderate.}, language = {en} } @misc{NaveedFloresRenteriaWeiss, author = {Naveed, Muhammad and Flores Renteria, Arturo and Weiß, Sabine}, title = {Role of alloying elements during thermocyclic oxidation of β/γ-TiAl alloys at high temperatures}, series = {Journal of Alloys and Compounds}, volume = {691}, journal = {Journal of Alloys and Compounds}, issn = {0925-8388}, doi = {10.1016/j.jallcom.2016.08.259}, pages = {489 -- 497}, abstract = {Gamma titanium aluminides are promising alloys known for their good mechanical properties and low densities, but their low oxidation resistance at high temperatures limits their application. This work discusses the thermocyclic oxidation behavior of newly developed β/γ-TiAl alloys at temperatures between 600 °C and 900 °C. An influence of β-stabilizing alloying elements like Nb and V on the oxidation of these alloys has been investigated here. The selected alloys are tested in an in-house developed thermocyclic furnace. The oxidation study is supported by gravimetric measurements along with Scanning Electron Microscopy (SEM) and Electron Diffraction Spectroscopy (EDS) mapping of the oxide layers. Additionally, phase formation after oxidation has been determined using X-Ray Diffraction (XRD). Results show that the Nb containing alloys are more oxidation resistant as compared to V containing alloys. The formation of a mixture of Al2O3 and TiO2 layers was found for all the alloys. The oxide kinetics controlled oxide growth and formation of various phases at different testing temperatures.}, language = {en} } @misc{BambachSizovaBolzetal., author = {Bambach, Markus and Sizova, Irina and Bolz, Sebastian and Weiß, Sabine}, title = {Devising Strain Hardening Models Using Kocks-Mecking Plots - A Comparison of Model Development for Titanium Aluminides and Case Hardening Steel}, series = {Metals}, volume = {6}, journal = {Metals}, number = {9}, issn = {2075-4701}, doi = {10.3390/met6090204}, pages = {204}, language = {en} } @misc{NaveedObrosovZaketal., author = {Naveed, Muhammad and Obrosov, Aleksei and Zak, Andrzej and Dudzinski, Wlodzimierz and Volinsky, Alex A. and Weiß, Sabine}, title = {Sputtering Power Effects on Growth and Mechanical Properties of Cr2AlC MAX Phase Coatings}, series = {Metals}, volume = {6}, journal = {Metals}, number = {11}, issn = {2075-4701}, doi = {10.3390/met6110265}, pages = {265}, abstract = {Coating growth and mechanical properties of nanolamellar Cr2AlC coatings at various sputtering power were investigated in the present study. Cr2AlC coating was deposited on the IN 718 superalloy and (100) Si wafers by DC magnetron sputtering at different sputtering powers. The structure and properties were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nanoindentation. It was found that coatings had columnar structure with nanocrystalline substructure. Deposition rate increased with the sputtering power. XRD results showed the presence of the Cr2AlC MAX phase, intermetallic AlCr2 and Cr7C3 carbide phases, along with the change in preferential coating growth orientation. TEM observations confirmed the occurrence of these phases, and the SAED patterns demonstrated significant texture of the coatings. Hardness values were measured in the range between 11-14 GPa, showing a slight increase with the sputtering power.}, language = {en} } @misc{ObrosovNaveedVolinskyetal., author = {Obrosov, Aleksei and Naveed, Muhammad and Volinsky, Alex A. and Weiß, Sabine}, title = {Substrate Frequency Effects on CrxN Coatings Deposited by DC Magnetron Sputtering}, series = {Journal of Materials Engineering and Performance}, volume = {26}, journal = {Journal of Materials Engineering and Performance}, number = {1}, issn = {1544-1024}, doi = {10.1007/s11665-016-2426-4}, pages = {366 -- 373}, abstract = {Controlled ion bombardment is a popular method to fabricate desirable coating structures and modify their properties. Substrate biasing at high frequencies is a possible technique, which allows higher ion density at the substrate compared with DC current bias. Moreover, high ion energy along with controlled adatom mobility would lead to improved coating growth. This paper focuses on a similar type of study, where effects of coating growth and properties of DC magnetron-sputtered chromium nitride (CrxN) coatings at various substrate bias frequencies are discussed. CrxN coatings were deposited by pulsed DC magnetron sputtering on Inconel 718 and (100) silicon substrates at 110, 160 and 280 kHz frequency at low duty cycle. Coating microstructure and morphology were studied by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), scratch adhesion testing and nanoindentation. Results indicate a transformation of columnar into glassy structure of CrxN coatings with the substrate bias frequency increase. This transformation is attributed to preferential formation of the Cr2N phase at high frequencies compared with CrN at low frequencies. Increase in frequency leads to an increase in deposition rate, which is believed to be due to increase in plasma ion density and energy of the incident adatoms. An increase in coating hardness along with decrease in elastic modulus was observed at high frequencies. Scratch tests show a slight increase in coating adhesion, whereas no clear increase in coating roughness can be found with the substrate bias frequency.}, language = {en} } @misc{ObrosovGulyaevZaketal., author = {Obrosov, Aleksei and Gulyaev, Roman and Zak, Andrzej and Ratzke, Markus and Naveed, Muhammad and Dudzinski, Wlodzimierz and Weiß, Sabine}, title = {Chemical and Morphological Characterization of Magnetron Sputtered at Different Bias Voltages Cr-Al-C Coatings}, series = {Materials}, volume = {10}, journal = {Materials}, number = {2}, issn = {1996-1944}, doi = {10.3390/ma10020156}, pages = {156}, abstract = {MAX phases (M = transition metal, A = A-group element, and X = C/N) are of special interest because they possess a unique combination of the advantages of both metals and ceramics. Most attention is attracted to the ternary carbide Cr2AlC because of its excellent high-temperature oxidation, as well as hot corrosion resistance. Despite lots of publications, up to now the influence of bias voltage on the chemical bonding structure, surface morphology, and mechanical properties of the film is still not well understood. In the current study, Cr-Al-C films were deposited on silicon wafers (100) and Inconel 718 super alloy by dc magnetron sputtering with different substrate bias voltages and investigated using Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), Atomic Force Microscopy (AFM), and nanoindentation. Transmission Electron Microscopy (TEM) was used to analyze the correlation between the growth of the films and the coating microstructure. The XPS results confirm the presence of Cr2AlC MAX phase due to a negative shift of 0.6-0.9 eV of the Al2p to pure aluminum carbide peak. The XRD results reveal the presence of Cr2AlC MAX Phase and carbide phases, as well as intermetallic AlCr2. The film thickness decreases from 8.95 to 6.98 µm with increasing bias voltage. The coatings deposited at 90 V exhibit the lowest roughness (33 nm) and granular size (76 nm) combined with the highest hardness (15.9 GPa). The ratio of Al carbide to carbide-like carbon state changes from 0.12 to 0.22 and correlates with the mechanical properties of the coatings. TEM confirms the columnar structure, with a nanocrystalline substructure, of the films.}, language = {en} } @misc{ObrosovGulyaevRatzkeetal., author = {Obrosov, Aleksei and Gulyaev, Roman and Ratzke, Markus and Volinsky, Alex A. and Bolz, Sebastian and Naveed, Muhammad and Weiß, Sabine}, title = {XPS and AFM Investigations of Ti-Al-N Coatings Fabricated Using DC Magnetron Sputtering at Various Nitrogen Flow Rates and Deposition Temperatures}, series = {Metals}, volume = {7}, journal = {Metals}, number = {2}, issn = {2075-4701}, doi = {10.3390/met7020052}, pages = {52}, abstract = {Ti-Al-N coatings were deposited by direct current magnetron sputtering (DCMS) onto IN 718 at different nitrogen flow rates and deposition temperatures. The coatings' properties were characterized using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) as well as nanoindentation. It was found that higher deposition temperature leads to higher surface roughness and nitrogen flux influences the shape of grains. According to XPS, the bonding structure of all coatings exhibited the (Ti,Al)N phase. Mechanical properties depend on the Al content within the films. The coating with the best mechanical properties (deposited at 500 °C and 20 standard cubic centimeters per minute (sccm)) was further deposited onto tungsten carbide (WC) cutting tools for cylindrical turning experiments. A quasi-constant flank wear was observed until a machining volume of 23,500 mm³.}, language = {en} } @inproceedings{SchulzeSeidlitzKoenigetal., author = {Schulze, Marcus and Seidlitz, Holger and K{\"o}nig, Franziska and Weiß, Sabine}, title = {Nanoindentation measurements of PVD coated multilayer constructions}, series = {Programme and proceedings of the 22nd Winter International Scintific Conference on Achivements in Mechanical and Materials Engineering (AMME'15), Gliwice - Zakopane (Poland), 2015}, booktitle = {Programme and proceedings of the 22nd Winter International Scintific Conference on Achivements in Mechanical and Materials Engineering (AMME'15), Gliwice - Zakopane (Poland), 2015}, editor = {Dobrzański, Leszek A.}, publisher = {Gliwice}, address = {International OCSCO World Press}, isbn = {978-83-63553-39-5}, language = {en} } @misc{ObrosovSutyginaVolinskyetal., author = {Obrosov, Aleksei and Sutygina, Alina and Volinsky, Alex A. and Manakhov, Anton and Weiß, Sabine and Kashkarov, Egor B.}, title = {Effect of Hydrogen Exposure on Mechanical and Tribological Behavior of CrₓN Coatings Deposited at Different Pressures on IN718}, series = {Materials}, volume = {10}, journal = {Materials}, number = {5}, issn = {1996-1944}, doi = {10.3390/ma10050563}, pages = {563}, abstract = {In the current study, the properties of the CrₓN coatings deposited on the Inconel 718 superalloy using direct current reactive magnetron sputtering are investigated. The influence of working pressure on the microstructure, mechanical, and tribological properties of the CrₓN coatings before and after high-temperature hydrogen exposure is studied. The cross-sectional scanning electron micrographs indicate the columnar structure of the coatings, which changes from dense and compact columns to large columns with increasing working pressure. The Cr/N ratio increases from 1.4 to 1.9 with increasing working pressure from 300 to 900 mPa, respectively. X-ray diffraction analysis reveals a change from mixed hcp-Cr₂N and fcc-CrN structure to approximately stoichiometric Cr₂N phase. After gas-phase hydrogenation, the coating deposited at 300 mPa exhibits the lowest hydrogen absorption at 600 °C of all investigated coatings. The results indicate that the dense mixed cubic and hexagonal structure is preferential for hydrogen permeation resistance due to the presence of cubic phase with higher packing density in comparison to the hexagonal structure. After hydrogenation, no changes in phase composition were observed; however, a small amount of hydrogen is accumulated in the coatings. An increase of coating hardness and elastic modulus was observed after hydrogen exposure. Tribological tests reveal that hydrogenation leads to a decrease of the friction coefficient up to 20\%-30\%. The best value of 0.25 was reached for hydrogen exposed CrₓN coating deposited at 300 mPa.}, language = {en} } @inproceedings{ObrosovKashkarovWeissetal., author = {Obrosov, Aleksei and Kashkarov, Egor B. and Weiß, Sabine and Volinsky, Alex A.}, title = {Mechanical and tribological behaviour of hydrogenated CrxN coatings deposited at different pressure and voltages on IN718}, series = {American Advanced Materials Congress 2016}, booktitle = {American Advanced Materials Congress 2016}, editor = {Tiwari, Ashutosh}, publisher = {VBRI Press}, address = {Link{\"o}ping}, isbn = {978-91-88252-03-6}, abstract = {Hydrogen degradation is a serious problem in industrial applications like power plants (boilers, turbines), marine structures, car and aircraft components, as it leads to failures as well as to deterioration of properties. Inconel 718 is one of the most commonly used materials for these applications. Different metal nitrides like TiN coatings have been deposited in past to prevent hydrogen degradation, which are also known for their high hardness and good wear resistance [1, 2]. However, reports on hydrogen degradation of CrN coatings, which shows better oxidation and corrosion resistance, higher temperature stability and lower friction coefficient than TiN [3, 4] has not been reported till now. Despite a lot of publications about CrN films, up to now the effect of hydrogenation on mechanical and tribological properties of CrN coatings is still not completely understood. In the current work CrxN coatings were deposited by Direct Current Magnetron Sputtering (dcMS) on Inconel 718 substrate at different chamber pressures and substrate voltages. Substrate voltage is one of the most important process parameters which determines the structure of the coating and the adhesion between substrate and coating. Simultaneously a study of the chamber pressure is also needed to understand the deposited structure and growth rate because at higher pressures the high number of argon atoms reduce the number of ionized ions available for the deposition leading to low deposition rates [5]. Gas-phase hydrogenation of the samples was performed at a temperature of 600° C and hydrogen pressure of 2 atm. It was found that CrxN coatings are resistant against hydrogen exposure as compared to uncoated surfaces. The results of changes in the mechanical, tribological properties and phase composition of the coatings after hydrogenation are discussed. Coating microstructure was studied by scanning electron microscopy (SEM). The mechanical properties of the coatings were characterized by means of nanoindentation and scratch test.}, language = {en} } @misc{ObrosovNaveedKruppetal., author = {Obrosov, Aleksei and Naveed, Muhammad and Krupp, Ulrich and Solovev, Mikhail and Weiß, Sabine}, title = {Investigation of TiAlN HiPIMS coating deposited on the newly developed Ni-based superalloy AD730}, abstract = {The development of new alloys for gas turbine engines has been focused on withstanding against increasing service temperatures. AD730™ is a recently developed nickel-based superalloy for turbine disk applications with superior properties at 700°C, which is higher than the common service temperature for IN718. Use of coatings to enhance the properties of materials, such as wear resistance is widely known in various applications. This research presents an experimental study of TiAlN coatings, deposited onto AD730 superalloy using High Power Impulse Magnetron Sputtering (HiPIMS). Phase structure and chemical composition of the TiAlN films were characterized by X-ray diffractometry. Transmission electron microscopy as well as scanning electron microscopy were used to analyze the microstructure of the coating. Mechanical properties, including hardness, Young's modulus, and adhesion strength were measured using nanoindentation und scratch test.}, language = {en} } @misc{ObrosovNaveedWeiss, author = {Obrosov, Aleksei and Naveed, Muhammad and Weiß, Sabine}, title = {Effect of pulse time on structure and mechanical properties of HPPMS deposited AlTiN coatings}, abstract = {The use of PVD AlTiN as a protective coating on cutting tools is well known. With the introduction of pulsed deposition techniques like High Power Pulsed Sputtering (HPPMS), a possibility is provided to the coating developers to design their coatings by the variation in pulse parameters. To analyze the effect of pulse time HPPMS AlTiN coatings were deposited on Si (100) as well as 100Cr6 steel plates at a temperature of 500°C in a reactive gas environment. Oscilloscope measurements depicted a change in current-voltage characteristics with variation in pulse time. This influence the coating structure, deposition rates and phase formations as well. Nanoindentation results show a variation in the mechanical properties of the coatings with the change in pulse time. This study focuses on the potential of HPPMS technology for enhancement of mechanical and structural properties of AlTiN coating.}, language = {en} } @inproceedings{BambachSizovaBolzetal., author = {Bambach, Markus and Sizova, Irina and Bolz, Sebastian and Weiß, Sabine}, title = {Development of a dynamic recrystallization model for a β-solidifying titanium aluminide alloy using Kocks-Mecking plots}, series = {ESAFORM 2016, proceedings of the 19th International ESAFORM Conference on Material Forming, Nantes, France, 27-29 April 2016}, booktitle = {ESAFORM 2016, proceedings of the 19th International ESAFORM Conference on Material Forming, Nantes, France, 27-29 April 2016}, publisher = {AIP Publishing}, address = {Melville, New York}, isbn = {978-0-7354-1427-3}, doi = {10.1063/1.4963545}, pages = {160002-1 -- 160002-7}, language = {en} } @misc{KashkarovNikitenkovSutyginaetal., author = {Kashkarov, Egor B. and Nikitenkov, Nikolay and Sutygina, Alina and Laptev, Roman and Bordulev, Yuriy and Obrosov, Aleksei and Liedke, Maciej O. and Zak, Andrzej and Weiß, Sabine}, title = {Microstructure, defect structure and hydrogen trapping in zirconium alloy Zr-1Nb treated by plasma immersion Ti ion implantation and deposition}, series = {Journal of Alloys and Compounds}, volume = {732}, journal = {Journal of Alloys and Compounds}, issn = {0925-8388}, doi = {10.1016/j.jallcom.2017.10.151}, pages = {80 -- 87}, abstract = {The effect of low energy plasma immersion ion implantation and deposition of titanium on microstructure, defect structure and hydrogen trapping in zirconium alloy Zr-1Nb was studied. Defect structure and distribution were analyzed by Doppler broadening using slow positron beam. The surface microstructure after modification is represented by nanostructured Ti grains with random orientation. The gradient distribution of titanium as well as vacancy type defects were analyzed. The concentration of vacancy type defects is rising with increasing bias voltage. Gas-phase hydrogenation of the Ti-modified Zr-1Nb alloy was performed at 400 °C for 60 min. The strong interaction of hydrogen with vacancy type defects was demonstrated. Two different changes in the defect structure after hydrogenation were observed: when a titanium film is formed on the surface (after deposition at 500 V) hydrogen trapping occurs with the formation of titanium hydride phases, while in the implanted layer (deposition at 1000 and 1500 V) hydrogen is trapped due to interaction with vacancy type defects. The physical basis of Ti diffusion and its influence on the evolution of defect structure after surface modification and hydrogenation were discussed.}, language = {en} } @misc{ShulepovKashkarovStepanovetal., author = {Shulepov, Ivan A. and Kashkarov, Egor B. and Stepanov, Igor B. and Syrtanov, Maxim S. and Sutygina, Alina and Shanenkov, Ivan and Obrosov, Aleksei and Weiß, Sabine}, title = {The Formation of Composite Ti-Al-N Coatings Using Filtered Vacuum Arc Deposition with Separate Cathodes}, series = {Metals}, volume = {7}, journal = {Metals}, number = {11}, issn = {2075-4701}, doi = {10.3390/met7110497}, pages = {13}, abstract = {Ti-Al-N coatings were deposited on high-speed steel substrates by filtered vacuum arc deposition (FVAD) during evaporation of aluminum and titanium cathodes. Distribution of elements, phase composition, and mechanical properties of Ti-Al-N coatings were investigated using Auger electron spectroscopy (AES), X-ray diffraction (XRD), transmission electron microscopy (TEM) and nanoindentation, respectively. Additionally, tribological tests and scratch tests of the coatings were performed. The stoichiometry of the coating changes from Ti0.6Al0.4N to Ti0.48Al0.52N with increasing aluminum arc current from 70 A to 90 A, respectively. XRD and TEM showed only face-centered cubic Ti-Al-N phase with preferred orientation of the crystallites in (220) direction with respect to the sample normal and without precipitates of AlN or intermetallics inside the coatings. Incorporation of Al into the TiN lattice caused shifting of the (220) reflex to a higher 2θ angle with increasing Al content. Low content and size of microdroplets were obtained using coaxial plasma filters, which provides good mechanical and tribological properties of the coatings. The highest value of microhardness (36 GPa) and the best wear-resistance were achieved for the coating with higher Al content, thus for Ti0.48Al0.52N. These coatings exhibit good adhesive properties up to 30 N load in the scratch tests.}, language = {en} } @misc{SeverinNaveedWeiss, author = {Severin, Stefanie and Naveed, Muhammad and Weiß, Sabine}, title = {Effect of HPPMS pulse-frequency on plasma discharge and deposited AlTiN coating properties}, series = {Advances in Materials Science and Engineering}, volume = {2017}, journal = {Advances in Materials Science and Engineering}, issn = {1687-8442}, pages = {18}, abstract = {Coatings like TiAlN (titanium content more than 50 \%) or AlTiN (aluminium content more than 50 \%) are well established as hard and wear resistant tool coatings, often prepared by physical vapour deposition (PVD) like arc evaporation or direct current magnetron sputtering (dcMS). With increasing challenges of operating conditions, a constant need in improvement of mechanical properties is required to withstand extreme loading conditions. This can be obtained by a higher amount of ionized sputtered metal atoms during the deposition process. To increase the metal-ion flux a high-power pulse magnetron sputtering (HPPMS) was developed. In order to understand the relation between HPPMS process parameters and mechanical properties of the AlTiN coatings, the present study discusses how different pulse frequencies (for a constant pulse length) influence AlTiN coating structure growth and their mechanical properties. In addition, film deposition rate and phase formation are influenced by altering process parameters like pulse length and frequency. Hence, different pulse-frequencies produce specific coatings with corresponding properties for functional requirements. Based on the established findings, answers to new scientific queries along with the demand to further optimize these coatings for tool applications are required.}, language = {en} } @misc{DonchevaBambachBambachSviridovetal., author = {Doncheva Bambach, Margarita and Bambach, Markus and Sviridov, Alexander and Weiß, Sabine}, title = {New process chains involving additive manufacturing and metal forming - a chance for saving energy?}, series = {Procedia Engineering}, volume = {207}, journal = {Procedia Engineering}, issn = {1877-7058}, doi = {10.1016/j.proeng.2017.10.1049}, pages = {1176 -- 1181}, language = {en} } @misc{ObrosovSutyginaManakhovetal., author = {Obrosov, Aleksei and Sutygina, Alina and Manakhov, Anton and Bolz, Sebastian and Weiß, Sabine and Kashkarov, Egor B.}, title = {Oxidation Behavior of Zr-1Nb Corroded in Air at 400 °C after Plasma Immersion Titanium Implantation}, series = {Metals}, volume = {8}, journal = {Metals}, number = {1}, issn = {2075-4701}, doi = {10.3390/met8010027}, pages = {16}, abstract = {In this paper, the influence of plasma immersion titanium implantation into the zirconium alloy Zr-1Nb on the oxidation behavior at 400 °C for 5, 24, 72, and 240 h in air under normal atmospheric pressure (101.3 kPa) was shown. The influence of implantation on the protective properties of the modified layer was shown. The valence of the oxides before and after implantation was analyzed by means of X-ray photoelectron spectroscopy (XPS). Grazing incidence X-ray diffraction (GIXRD) was carried out to examine the phase composition after titanium ion implantation and oxidation. Differential scanning calorimetry (DSC) revealed that titanium implantation exhibited effects of stabilizing the β phase. The formation of the t-ZrO2 and m-ZrO2 was observed during the oxidation of the as-received and modified Zr-1Nb. The measurement of weight gain showed an improvement in oxidation resistance of Ti implanted Zr-1Nb at the oxidation up to 24 h when compared with that of the as-received Zr-1Nb. However, at longer oxidation cycle the oxidation rate of Ti-implanted zirconium alloy is the same with the as-received alloy, which attributed to the layer thickness. Nevertheless, the corrosion of the Ti-implanted alloy is more uniform, while a local corrosion and cracks was detected on the surface of the as-received alloy.}, language = {en} } @misc{KashkarovNikitenkovSutyginaetal., author = {Kashkarov, Egor B. and Nikitenkov, Nikolay and Sutygina, Alina and Obrosov, Aleksei and Manakhov, Anton and Polčak, Josef and Weiß, Sabine}, title = {Hydrogen absorption by Ti-implanted Zr-1Nb alloy}, series = {International journal of hydrogen energy}, volume = {43}, journal = {International journal of hydrogen energy}, number = {4}, issn = {0360-3199}, doi = {10.1016/j.ijhydene.2017.12.003}, pages = {2484 -- 2491}, abstract = {This paper describes the hydrogenation behavior of Zr-1Nb alloy Ti-implanted by plasma immersion ion implantation (PIII). Hydrogen sorption kinetics of the Ti-modified alloy was investigated under gas-phase hydrogenation at 400 °C for 1 h. The influence of implantation time on the protective properties of the modified layer was shown. The lowest hydrogen absorption as well as the highest hydrogen trapping efficiency was achieved after PIII for 30 min. The main contribution to the reduction of hydrogen permeation is the formation of an oxide layer consisting of mixed TiO2 and ZrO2 on the modified surface of the alloy. X-ray photoelectron spectroscopy (XPS) revealed that PIII titanium oxide exists on the surface in the form of TiO2, which transforms to mixed Ti2O3 and TiO2 after hydrogenation. The thickness of the modified layer increases with implantation time that improves the efficiency of hydrogen trapping. All the absorbed hydrogen is gradually distributed in the modified layer and no hydrides are formed after hydrogenation in Ti-modified Zr-1Nb for 15 and 30 min.}, language = {en} } @misc{KashkarovObrosovSutyginaetal., author = {Kashkarov, Egor B. and Obrosov, Aleksei and Sutygina, Alina and Uludintceva, Elena and Mitrofanov, Andrei and Weiß, Sabine}, title = {Hydrogen Permeation, and Mechanical and Tribological Behavior, of CrNx Coatings Deposited at Various Bias Voltages on IN718 by Direct Current Reactive Sputtering}, series = {Coatings}, volume = {8}, journal = {Coatings}, number = {2}, issn = {2079-6412}, doi = {10.3390/coatings8020066}, pages = {12}, abstract = {In the current work, the microstructure, hydrogen permeability, and properties of chromium nitride (CrNₓ) thin films deposited on the Inconel 718 superalloy using direct current reactive sputtering are investigated. The influence of the substrate bias voltage on the crystal structure, mechanical, and tribological properties before and after hydrogen exposure was studied. It was found that increasing the substrate bias voltage leads to densification of the coating. X-ray diffraction (XRD) results reveal a change from mixed fcc-CrN + hcp-Cr₂N to the approximately stoichiometric hcp-Cr₂N phase with increasing substrate bias confirmed by wavelength-dispersive X-ray spectroscopy (WDS). The texture coefficients of (113), (110), and (111) planes vary significantly with increasing substrate bias voltage. The hydrogen permeability was measured by gas-phase hydrogenation. The CrN coating deposited at 60 V with mixed c-CrN and (113) textured hcp-Cr₂N phases exhibits the lowest hydrogen absorption at 873 K. It is suggested that the crystal orientation is only one parameter influencing the permeation resistance of the CrNx coating together with the film structure, the presence of mixing phases, and the packing density of the structure. After hydrogenation, the hardness increased for all coatings, which could be related to the formation of a Cr₂O₃ oxide film on the surface, as well as the defect formation after hydrogen loading. Tribological tests reveal that hydrogenation leads to a decrease of the friction coefficient by up to 40\%. The lowest value of 0.25 ± 0.02 was reached for the CrNₓ coating deposited at 60 V after hydrogenation.}, language = {en} } @misc{EvdokimovObrosovOssenbrinketal., author = {Evdokimov, Anton and Obrosov, Aleksei and Ossenbrink, Ralf and Weiß, Sabine and Michailov, Vesselin}, title = {Mechanical properties of dissimilar steel-aluminum weld}, series = {Materials Science and Engineering: A}, volume = {Volume 722}, journal = {Materials Science and Engineering: A}, issn = {0921-5093}, doi = {https://doi.org/10.1016/j.msea.2018.03.019}, pages = {242 -- 254}, abstract = {Knowledge of the properties of dissimilar welds is of great significance for the development of multi-material lightweight structures. In this study, stainless steel (1.4301) and aluminum alloy (6082-T6) sheets were welded in overlap configuration in keyhole mode. The resulting weld metals were investigated with respect to their mechanical properties. Several samples were cut out of different locations along the welds and their cross-sections were subjected to indentation testing and energy dispersive X-ray (EDS) analysis. Young's modulus E, yield stress σy, and strain hardening exponent n, were determined by means of reverse analysis of the indentation load (P) - depth (h) curves, allowing construction of true stress - true strain relations. An essential increase in yield stress in comparison to the one of the base alloys was observed inside the weld metal. In contrary, Young's modulus and strain hardening exponent of the welds were almost identical to corresponding values of the base steel metal. Due to the sensitivity of yield stress to the aluminum content, slight variations of the welding parameters lead to significant changes in elastic-plastic behavior of the weld metal.}, language = {en} } @misc{ObrosovSutyginaKashkarovetal., author = {Obrosov, Aleksei and Sutygina, Alina and Kashkarov, Egor B. and Weiß, Sabine}, title = {Oxidation behavior of Zr-1Nb in air at 400°C after Titanium Plasma Immersion Ion Implantation}, pages = {1}, abstract = {Zirconium alloys have been widely used in nuclear reactors due to low thermal neutron capture cross-section, excellent corrosion resistance and acceptable mechanical properties [1, 2]. Nowadays several methods apply for improving hydrogen and corrosion resistance such as addition of stabilizing additives (yttrium) [3, 4], deposition of thin solid films [5, 6], micro-arc oxidation [7] and modification of the surface by electron beam [8, 9]. Despite the multiplicity of the methods hydrogen embrittlement is still a pressing issue. Previous results [10, 11] have shown the positive influence of plasma immersion titanium implantation on the hydrogenation behavior of Zr-1Nb and Zr-2.5 Nb. After Ti implantation hydrogen preferably accumulates in the modified surface layer comprising the implanted Ti. Furthermore, the hydrogen concentration is considerably less inside the zirconium modified sample than in the as-received samples. The integration of elements into the zirconium lattice can influence the valence of the surface and change corrosion and oxidation rates of the alloys. So it is very important not to decrease the zirconium oxidation resistance due to Ti implantation. Therefore, the purpose of this research is to study of the influence of Ti implantation on surface morphology, oxidation rate and phase structure of the Zr-1Nb alloy after oxidation on air at 400 0C for 5, 24, 72 and 240 h. The surface structure of the samples and their elemental composition were investigated with the scanning electron microscope Mira II XMH (Tescan) with energy dispersive x-ray spectroscopy system (EDS). X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC) as well as X-ray diffraction (XRD) was used to characterise the influence of titanium implantation on the oxidation behaviour. The results show that the oxidation kinetics after Ti modification of the zirconium alloy changed. Although the weight gain of the implanted sample remains approximately the same, it can be considered that Ti implantation stabilizes the oxide layer and has beneficial influence on the oxidation protection of Zr-1Nb.}, language = {en} } @misc{AbangWeissKrautz, author = {Abang, Roger Atini and Weiß, Sabine and Krautz, Hans Joachim}, title = {Impact of increased power plant cycling on the oxidation and corrosion of coal-fired superheater materials}, series = {Fuel}, volume = {2018}, journal = {Fuel}, number = {220}, issn = {0016-2361}, doi = {10.1016/j.fuel.2018.02.047}, pages = {521 -- 534}, abstract = {As power generation from variable renewable energy sources such as wind and solar power continues to increase in the future, fewer baseload power plants will be needed. As a result, high operational flexibility is becoming a vital requirement for conventional power plants to allow for the smooth integration of the variable renewable energy sources (v-RES) into the grid. To understand the impact of high operational flexibility (increased cycling) for coal-fired power plant materials, five commercial coal boiler superheater and reheater materials were investigated under isothermal and cyclic conditions for 1000 h each. The candidate alloys investigated were: T91, VM12-SHC, TP347-HFG, DMV304 HCu and DMV310 N. The results (weight change kinetics and metallographic analysis) after exposure at a metal surface temperature of 650 °C clearly showed the impact of increased flexibility on the corrosion and oxidation of the materials. Oxide growth (weight gain), metal loss, oxide spallation, and grain boundary attack were found to be more severe under cyclic conditions than under isothermal conditions.}, language = {en} } @misc{SanthanakrishnanBalakrishnanSeidlitzWeiss, author = {Santhanakrishnan Balakrishnan, Venkateswaran and Seidlitz, Holger and Weiß, Sabine}, title = {Layup Configuration Effect on Notch Residual Strength in Composite Laminates}, series = {Materials}, volume = {11}, journal = {Materials}, number = {2}, issn = {1996-1944}, doi = {10.3390/ma11020308}, pages = {12}, abstract = {The current trend shows an increasing demand for composites due to their high stiffness to weight ratio and the recent progress in manufacturing and cost reduction of composites. To combine high strength and stiffness in a cost-effective way, composites are often joined with steel or aluminum. However, joining of thermoset composite materials is challenging because circular holes are often used to join them with their metal counterparts. These design based circular holes induce high stress concentration around the hole. The purpose of this paper is to focus on layup configuration and its impact on notch stress distribution. To ensure high quality and uniformity, the holes were machined by a 5 kW continuous wave (cw) CO2 laser. The stress distribution was evaluated and compared by using finite element analysis and Lekhnitskii's equations. For further understanding, the notch strength of the laminates was compared and strain distributions were analyzed using the digital image correlation technique.}, language = {en} } @misc{KashkarovRyabchikovKurochkinetal., author = {Kashkarov, Egor B. and Ryabchikov, Alexander I. and Kurochkin, Alexander and Syrtanov, Maxim S. and Shevelev, Alexey and Obrosov, Aleksei and Weiß, Sabine}, title = {Hydrogen Interaction with Deep Surface Modified Zr-1Nb Alloy by High Intensity Ti Ion Implantation}, series = {Metals}, volume = {8}, journal = {Metals}, number = {12}, issn = {2075-4701}, doi = {10.3390/met8121081}, abstract = {A deep surface modified TiZr layer was fabricated by high-intensity low-energy titanium ion implantation into zirconium alloy Zr-1Nb. Gas-phase hydrogenation was performed to evaluate protective properties of the modified layer against hydrogen permeation into Zr-1Nb alloy. The effects of ion implantation and hydrogen on microstructure, phase composition and elemental distribution of TiZr layer were analyzed by scanning electron microscopy, X-ray diffraction, and glow-discharge optical emission spectroscopy, respectively. It was revealed that TiZr layer (~10 μm thickness) is represented by α′ + α(TiZr) lamellar microstructure with gradient distribution of Ti through the layer depth. It was shown that the formation of TiZr layer provides significant reduction of hydrogen uptake by zirconium alloy at 400 and 500 °C. Hydrogenation of the modified layer leads to refinement of lamellar plates and formation of more homogenous microstructure. Hydrogen desorption from Ti-implanted Zr-1Nb alloy was analyzed by thermal desorption spectroscopy. Hydrogen interaction with the surface modified TiZr layer, as well as its resistance properties, are discussed.}, language = {en} }