TY - JOUR A1 - Miclosina, Calin-Octavian A1 - Belu-Nica, Remus A1 - Ciubotariu, Costel-Relu A1 - Marginean, Gabriela T1 - Processing and Evaluation of an Aluminum Matrix Composite Material JF - Journal of Composites Science N2 - Abstract This study signifies the development and characterization of a composite material with a metallic matrix of aluminum reinforced with a steel mesh, utilizing centrifugal casting technology. An evaluation was conducted to ascertain the influence of the formulation process and the presence of the insert on the mechanical behavior with regard to tensile strength. The aluminum matrix was obtained from commercial and scrap alloys, elaborated by advanced methods of degassing and chemical modification. Meanwhile, the steel mesh reinforcement was cleaned, copper plated, and preheated to optimize wetting and, consequently, adhesion. The structural characterization was performed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy analyses (EDX), which highlighted a well-defined interface and uniform copper distribution. The composite was produced by means of horizontal-axis centrifugal casting in a fiberglass mold, followed by cold rolling to obtain flat specimens. A total of eight tensile specimens were examined, with measured ultimate tensile strengths ranging from 78.5 to 119.8 (MPa). A thorough examination of the fractured specimens revealed a brittle fracture mechanism, devoid of substantial plastic deformation. The onset of failures was frequently observed at the interface between the aluminum matrix and the steel mesh. The use of SEM and EDX investigations led to the confirmation of the uniformity of the copper coating and the absence of significant porosity or interfacial defects. A bimodal distribution of tensile strength values was observed, a phenomenon that is likely attributable to variations in mesh positioning and local differences in solidification. A correlation was established between the experimental results and an analytical polynomial model, thereby confirming a reasonable fit. In sum, the present study provides a substantial foundation for the development of metal matrix composites with enhanced performance, specifically designed for challenging structural applications. This method also demonstrates potential for recycling aluminum scrap into high-performance composites with controlled microstructure and mechanical integrity. KW - composite material KW - aluminum matrix KW - steel mesh KW - centrifugal casting KW - tensile testing KW - microstructural characterization Y1 - 2025 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:1010-opus4-48135 VL - 2025 IS - 9(7), Special Issue Metal Composites, Volume II SP - 1 EP - 12 PB - MDPI ER - TY - JOUR A1 - Frunzaverde, Doina A1 - Marginean, Gabriela A1 - Ciubotariu, Costel-Relu T1 - Corrosion and Cavitation Performance of Flame-Sprayed NiCrBSi Composite Coatings Reinforced with Hard Particles JF - Crystals (Special Issue Modern Technologies in the Manufacturing of Metal Matrix Composites) N2 - To enhance the operational life of hydraulic machinery, protective coatings against wear, particularly cavitation erosion, and corrosion might be applied on the surfaces of components. The experiments conducted in this study aimed to assess the suitability of 80/20 NiCrBSi/WC-Co composite coatings for this purpose. A coating of NiCrBSi self-fluxing alloy, which served as the reference material, was deposited alongside a NiCrBSi coating reinforced with 20% WC-Co, both applied by flame spraying onto X3CrNiMo13-4 substrates, the martensitic stainless steel type frequently utilized in turbine blade manufacturing. The improved density of the coatings and adhesion to the substrate was achieved by remelting with an oxyacetylene flame. The cavitation and corrosion performance of both the reference and composite coating were evaluated through cavitation tests and electrochemical measurements conducted in the laboratory. The results demonstrate that the addition of 20% WC-Co significantly enhances the cavitation resistance of the composite material, as evidenced by the reduction to 3.76 times of the cumulative erosion (CE), while the stabilization rate remained at half the value observed for the reference self-fluxing alloy coating. Conversely, the addition of WC-Co into the NiCrBSi coating resulted in a slight decrease in the corrosion resistance of the self-fluxing alloy. Nevertheless, the corrosion rate of the composite coating (124.80 µm/year) did not significantly exceed the upper limit for excellent corrosion resistance (100 µm/year). KW - cavitation resistance KW - corrosion resistance KW - coatings KW - hydraulic machinery KW - self-fluxing alloys KW - NiCrBSi KW - WC-12Co KW - NiCrBSi/WC-Co composites Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:1010-opus4-47740 SN - 2073-4352 VL - 2024 IS - 14 (12) SP - 1 EP - 12 PB - MDPI ER - TY - JOUR A1 - Eßler, Julian A1 - Woelk, Dino Horst A1 - Utu, Ion-Dragos A1 - Marginean, Gabriela T1 - Impact of hBN Content on the Tribological Behavior and Thermal Diffusivity of HVOF-Sprayed Cr3C2-NiCr Coatings JF - Materials (Special Issue Advances in Tribological and Other Functional Properties of Materials) N2 - Considering the significant health risks posed by hard chrome plating during its application, thermally sprayed Cr3C2-NiCr cermet coatings represent a suitable alternative. Incorporating hexagonal boron nitride (hBN) as a dry lubricant into the feedstock powder can further enhance wear resistance and thermal conductivity, crucial for preventing premature failure caused by inadequate lubrication. In this study, the mass fraction of hBN was varied between 0 and 15 wt.% to assess its influence on the tribological performance of the coatings using pin-on-disk tests. The coating’s hardness was measured via the Vickers method, and its cracking tendency at the coating/substrate interface was evaluated. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were employed to analyze the microstructure and phase composition, while thermal diffusivity was determined using the laser flash method. The findings revealed that the inclusion of hBN, at concentrations of up to 10 wt.%, leads to an improvement in thermal diffusivity and a reduction in the coefficient of friction. However, exceeding this threshold leads to a decrease in hardness and increased crack formation tendency, highlighting the trade-off between frictional and mechanical properties. KW - boron nitride composite coatings KW - HVOF KW - Cr3C2-NiCr KW - sliding wear KW - thermal diffusivity Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:1010-opus4-47295 VL - 2024 IS - 17 (22) SP - 1 EP - 14 PB - MDPI ER - TY - JOUR A1 - Woelk, Dino Horst A1 - Eßler, Julian A1 - Utu, Ion-Dragos A1 - Marginean, Gabriela T1 - Comparative Corrosion and Wear Behaviors of Cermet Coatings Obtained from Conventional and Recycled Powders JF - Applied Sciences N2 - Many components in industry are subjected to high loads during operation and therefore often do not reach their intended service life. Conventional steels frequently do not provide sufficient protection against wear and corrosion. One solution is to coat these components using methods like thermal spraying to apply cermet coatings such as Cr3C2-NiCr or WC-Co-Cr. In light of increasingly strict environmental regulations, more eco-friendly alternatives are needed, especially ones that use little or no Cr, Ni, Co, or W. Another alternative is the recycling of powder materials, which is the focus of this research project. This study investigated whether filter dust from an HVOF system could be used to develop a new coating suitable for use in applications requiring resistance to wear and corrosion. This is challenging as the filter dusts have heterogeneous compositions and irregular particle sizes. Nevertheless, this recycled material, referred to as “Green Cermets” (GCs), offers previously untapped potential that may also be of ecological interest. An established WC-Co-Cr coating served as a reference. In addition to friction wear and corrosion resistance, the study also examined particle size distribution, hardness, microstructure, and susceptibility to crack formation at the interface and inside the coating. Even though the results revealed a diminished performance of the GC coatings relative to the conventional WC-CoCr, they may still be applicable in various industrial applications. KW - recycling KW - HVOF KW - WC-Co-Cr KW - thermal spraying KW - filter dust KW - corrosion KW - wear Y1 - 2025 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:1010-opus4-48157 VL - 2025 IS - 15(14), Special Issue Composites from Sustainable Resources: Properties, Manufacturing, and Applications SP - 1 EP - 16 PB - MDPI ER - TY - JOUR A1 - Anghel, Iasmina-Mădălina A1 - Pascu, Alexandru A1 - Hulka, Iosif A1 - Woelk, Dino Horst A1 - Utu, Ion-Dragos A1 - Marginean, Gabriela T1 - Characterization of Cobalt-Based Composite Multilayer Laser-Cladded Coatings JF - Crystals (Special Issue Crystallization of High Performance Metallic Materials (2nd Edition)) N2 - Laser cladding is an essential method for strengthening and restoring component surfaces. To increase its efficacy and provide a reliable surface treatment technique, it is necessary to optimize process parameters, enhance material adhesion, and guarantee high-quality, reliable coatings. These measures help to extend the lifespan of components. In this study, the surfaces of AISI 904L stainless steel samples were cladded to prepare various Co-based composite coatings with single and multiple layers reinforced with WC–CoCr–Ni powder. The phases within the newly developed layers were investigated using X-ray Diffraction (XRD), while the microstructure was examined using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX). Further tests were performed to assess the hardness, wear resistance and corrosion performance of the deposited coatings. Analyzing and comparing the coatings, it was observed that the coating performance increased with increasing thickness and generally due to a lower amount of Fe present within the microstructure. KW - laser cladding KW - CoCr-based coatings KW - wear KW - corrosion KW - hardness Y1 - 2025 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:1010-opus4-48757 SN - 2073-4352 VL - 2025 IS - 15 (11) PB - MDPI ER - TY - JOUR A1 - Muntean, Roxana A1 - Valean, Petru-Cristian A1 - Kazamer, Norbert A1 - Utu, Ion-Dragos A1 - Marginean, Gabriela A1 - Şerban, Viorel-Aurel T1 - Effect of Feedstock Powder Intrinsic Characteristics on the Tribological Behavior of Inductively Remelted NiCrBSi Flame-Sprayed Coatings JF - Lubricants N2 - Ni-based alloys are among the materials of choice in developing high-quality coatings for ambient and high temperature applications that require protection against intense wear and corrosion. The current study aims to develop and characterize NiCrBSi coatings with high wear resistance and improved adhesion to the substrate. Starting with nickel-based feedstock powders, thermally sprayed coatings were initially fabricated. Prior to deposition, the powders were characterized in terms of microstructure, particle size, chemical composition, flowability, and density. For comparison, three types of powders with different chemical compositions and characteristics were deposited onto a 1.7227 tempered steel substrate using oxyacetylene flame spraying, and subsequently, the coatings were inductively remelted. Ball-on-disc sliding wear testing was chosen to investigate the tribological properties of both the as-sprayed and induction-remelted coatings. The results reveal that, in the case of as-sprayed coatings, the main wear mechanisms were abrasive, independent of powder chemical composition, and correlated with intense wear losses due to the poor intersplat cohesion typical of flame-sprayed coatings. The remelting treatment improved the performance of the coatings in terms of wear compared to that of the as-sprayed ones, and the density and lower porosity achieved during the induction post-treatment had a significant positive role in this behavior. KW - NiCrBSi coatings KW - flame spraying; induction remelting KW - wear resistance Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:1010-opus4-45869 VL - 2023 (Special Issue Advances in Surface Engineering and Tribology) IS - 11 (9) PB - MDPI ER - TY - JOUR A1 - Rost, Ulrich A1 - Muntean, Roxana A1 - Marginean, Gabriela A1 - Merino, Cesar A1 - Diez, Roberto A1 - Vaszilcsin, Nicolae A1 - Brodmann, Michael T1 - Effect of Process Parameters for Oxygen Plasma Activation of Carbon Nanofibers on the Characteristics of Deposited Platinum Nanoparticles as Electrocatalyst in Proton Exchange Membrane Fuel Cells JF - International Journal of Electrochemical Science N2 - In the polymer electrolyte membrane fuel cells (PEMFC) state of the art, rare and expensive platinum group metals (PGM) or PGM alloys are used as catalyst material. Reduction of PGMs in PEMFC electrodes is strongly required to reach cost targets for this technology. An optimal catalyst utilization is achieved in case of nano-structured particles supported on carbon material with a large specific surface area. In this study, graphitic material, in form of carbon nanofibers (CNF), is decorated with Pt particles, serving as catalyst material for PEMFC electrodes with low Pt loading. As a novelty, the effect of oxygen plasma treatment of CNFs previously to platinum particle deposition has been studied. Electrodes are investigated in respect of the optimal morphology, microstructure as well as electrochemical properties. Therefore, samples are characterized by means of scanning electron microscopy combined with energy dispersive X-ray analysis, transmission electron microscopy, thermogravimetry, X-ray diffraction as well as X-ray fluorescence analysis. In order to determine the electrochemical active surface area of catalyst particles, cyclic voltammetry has been performed in 0.5 M sulphuric acid. Selected samples have been investigated in a PEMFC test bench according to their polarization behavior. KW - PEM fuel cell electrocatalysts KW - Carbon nanofibers KW - Oxygen plasma activation KW - Pulsed electroplating. Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:1010-opus4-9509 SN - 1452-3981 VL - 2016 IS - Volume 11, Issue 11 SP - 9110 EP - 9122 PB - Elsevier ER - TY - JOUR A1 - Pinger, Thomas A1 - Brand, Marco A1 - Grothe, Sonja A1 - Marginean, Gabriela T1 - Abrasive Wear Behavior of Batch Hot-Dip Galvanized Coatings JF - Materials (Special Issue Metal Coatings for Wear and Corrosion Applications (Second Edition)) N2 - In recent decades, batch hot-dip galvanized (HDG) steel has proven itself in practical applications due to the good corrosion resistance of its components. Despite the importance of the mechanical-load-bearing capacity of these coatings, the wear behavior has, so far, only been investigated very sporadically and not systematically, so a quantification of the wear behavior and statements on the mechanisms are vague. Therefore, two body wear tests with bonded abrasive grain were carried out. Varying the friction rolls, load, and total number of cycles, the wear behavior was investigated. The mass loss and the layer thickness reduction were measured at different intervals. After the test, the microstructure in the cross- section and the hardness according to Vickers (0.01 HV) were evaluated. The results showed that the wear behavior of HDG coatings against abrasive loads can be characterized with the selected test conditions. Initially, the applied load removed the soft η-phase. As the total number of cycles increases, the η- and ζ-phases deform plastically, resulting in a lower mass reduction compared to that expected from the measured layer thickness. The characteristic structure of a batch HDG coating with hard intermetallic Zn-Fe phases and an outer pure zinc phase has demonstrated effective resistance to abrasion. KW - batch hot-dip galvanizing KW - wear behavior KW - abrasion KW - zinc KW - coating Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:1010-opus4-45841 SN - 1996-1944 VL - 2024 IS - 17 (7) PB - MDPI ER - TY - JOUR A1 - Böhm, Leonard A1 - Cieluch, Maximilian A1 - Kazamer, Norbert A1 - Wirkert, Florian Josef A1 - Marginean, Gabriela A1 - Apfel, Ulf-Peter A1 - Brodmann, Michael T1 - Electrodeposition of Mo-Rich NiMo Catalysts: Effect of Deposition Parameters and Oxygen Content on the Alkaline Hydrogen Evolution Reaction Activity JF - ChemElectroChem N2 - Electrodeposited Mo-rich NiMo catalysts offer enhanced catalytic activity for the alkaline hydrogen evolution reaction (HER) and provide an electrically conductive, binder-free substrate connection, making them promising catalysts for green hydrogen production. However, creating Mo-rich deposits is challenging, as the codeposition process typically favors Ni. Optimal deposition conditions for Mo-rich NiMo catalysts remain insufficiently explored. This article investigates Mo-rich NiMo electrodeposition from an ammonia-free citrate bath using NaSO4 as a chlorine-free support electrolyte. The effects of the deposition parameters, 1) sodium molybdate concentration in the electrolyte, 2) deposition current density, and 3) enhanced mass transport via working electrode rotation on the alkaline HER activity, were studied. The electrodeposits, containing 44–66 wt% Mo, exhibited increased surface area due to a rough, cracked morphology and variable oxygen content of the catalyst. The oxygen content was linked to HER activity, revealing an inhibiting effect. The lowest overpotential of 118 mV at −10  mA cm−2 for the alkaline HER was achieved using an electrolyte with 0.02 mol L−1 sodium molybdate, a deposition current density of 600 mA cm−2, without electrode rotation. Respective samples combined a favorable Ni:Mo ratio comprising 56 wt% Mo content with increased surface area and low oxygen content. Y1 - 2025 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:1010-opus4-48327 VL - 2025 PB - Wiley-VCH ER - TY - JOUR A1 - Idir, Abdelhek A1 - Delloro, Francesco A1 - Younes, Rassim A1 - Bradai, Mohand Amokrane A1 - Sadeddine, Abdelhamid A1 - Marginean, Gabriela T1 - Comparative Study of Corrosion Performance of LVOF-Sprayed Ni-Based Composite Coatings Produced Using Standard and Reducing Flame Spray Stoichiometry JF - Materials (MDPI) N2 - Coating efficiency and quality can be significantly improved by carefully optimizing the coating parameters. Particularly in the flame spray method, the oxygen/fuel ratio, which is classified as oxidizing flame stoichiometry (excess oxygen) and reduces flame stoichiometry (excess acetylene), and spray distance are the most critical factors, as they correlate significantly with coating porosity and corrosion performance. Hence, understanding the effects of these parameters is essential to further minimize the porosity, improving the corrosion performance of thermally sprayed coatings. In this work, a NiWCrBSi alloy coating was deposited via the oxyacetylene flame spray/Flexicord-wire (FS/FC) method. The effect of the flame oxygen/fuel ratio and spray distance on the microstructure properties and corrosion behavior of the coatings was investigated. Afterwards, the microstructure, phases’ compositions, spray distance, and corrosion performance were studied. The equivalent circuit model was proposed, and the corrosion mechanism was discussed. The obtained results highlight that the oxygen-to-fuel ratio is a promising solution for the further application of flame spray/Flexicordwire (FS/FC) cermet coatings in hostile environments. Depending on the flame’s oxygen/fuel ratio, careful selection of the flame stoichiometry provides low porosity and high corrosion performance. KW - thermal spray; flame stoichiometry; microstructure; porosity; corrosion performance Y1 - 2024 U6 - https://doi.org/10.3390/ma17020458 VL - 17 (2024) IS - 2 ER - TY - CHAP A1 - Rost, Ulrich A1 - Marginean, Gabriela A1 - Muntean, Roxana A1 - Podleschny, Pit Yannick A1 - Brodmann, Michael A1 - Merino, Cesar A1 - Diez, Roberto ED - International Energy and Sustainability Conference , T1 - A cost-effective PEM fuel cell test system based on hydraulic compression with optimized platinum catalyst loading T2 - International Energy and Sustainability Conference (IESC), June 30 - July 1, 2016 N2 - For this study gas diffusion electrodes (GDE) with low platinum loading are prepared for the application as anode in polymer electrolyte membrane fuel cell (PEMFC) systems based on hydraulic compression. As catalyst support material, carbon nanofibers (CNF) are investigated because of their high specific surface area and high graphitization degree. The electrode preparation is optimized by an economic and environmental friendly pre-treatment process in oxygen plasma. For GDE manufacture an ink containing oxygen plasma activated CNFs as well as hydrophilic polymer is used. After spray coating of this CNF ink on a graphitic substrate, platinum is deposited using the pulse plating technique. Preliminary results showed a considerable improvement of CNF dispersibility as well as an increased amount and an optimized morphology of the deposited platinum. Morphology and microstructure are observed by scanning electron microscopy as well as transmission electron microscopy. Platinum loading is determined by thermogravimetric analysis to be in the range of 0.01 mg cm-2 to 0.017 mg cm-2. Furthermore, MEAs are prepared from these GDEs and testing is performed in a novel modular fuel cell test stack based on hydraulic compression. Technical information about stack design and functions is given in this work. KW - Hydraulic compression KW - Carbon Nano Fibers KW - PEM Fuel Cells KW - Catalyst utilization Y1 - 2016 SN - 978-1-5090-2980-8 U6 - https://doi.org/10.1109/IESC.2016.7569500 PB - IEEE CY - [Piscataway, NJ] ER - TY - JOUR A1 - Rost, Ulrich A1 - Muntean, Roxana A1 - Podleschny, Pit Yannick A1 - Marginean, Gabriela A1 - Brodmann, Michael A1 - Şerban, Viorel-Aurel T1 - Influence of the Graphitisation Degree of Carbon Nano Fibres Serving as Support Material for Noble Metal Electro Catalysts on the Performance of PEM Fuel Cells JF - Solid state phenomena N2 - In this experimental work polymer electrolyte membrane fuel cell (PEMFC) electrodes are analysed, which are prepared by the use of two sorts of carbon nano fibres (CNF) serving as support material for platinum nano particles. Those CNFs, which are heat treated subsequently to their production, have a higher graphitisation degree than fibres as produced. The improved graphitisation degree leads to higher electrical conductivity, which is favourably for the use in PEMFC electrodes. Samples have been analysed, in order to determine graphitisation degree, electrical conductivity, as well as morphology and loading of the prepared electro catalyst. Membrane electrode assemblies manufactured from prepared electrodes are analysed in-situ in a PEM fuel cell test environment. It has been determined that power output for samples containing CNFs with higher graphitisation degree is increased by about 13.5%. Y1 - 2016 U6 - https://doi.org/10.4028/www.scientific.net/SSP.254.27 IS - 254 SP - 27 EP - 32 ER - TY - CHAP A1 - Muntean, Roxana A1 - Pascal, Dragos-Toader A1 - Rost, Ulrich A1 - Podleschny, Pit Yannick A1 - Marginean, Gabriela A1 - Schumacher, Marc T1 - Studies on pulse electrodeposition of Pt-Ni binary alloy for electrochemical cell applications, 7th International Symposium on Advanced Materials and Structures T2 - Konferenz: 7th International Conference on Advanced Materials and Structures (AMS 2018), 28.-31. März 2018 in Timisoara (Rumänien) Y1 - 2018 ER - TY - JOUR A1 - Muntean, Roxana A1 - Rost, Ulrich A1 - Marginean, Gabriela A1 - Vaszilcsin, Nicolae T1 - Optimisation of the Electrodeposition Parameters for Platinum Nanoparticles on Carbon Nanofibers Support JF - Solid state phenomena N2 - Platinum nanoparticles electrodeposition on carbon nanofibers (CNF) support has been performed with the purpose to obtain electrodes that can be further used especially in a polymer electrolyte membrane fuel cell (PEMFC). A pretreatment of CNF is required in order to enhance the surface energy, which simultaneously improves handling and wettability as well as interaction with the platinum cations. This step was performed using oxygen plasma functionalization. To produce CNF supported Pt catalysts, an electrochemical method was applied and the deposition parameters were adjusted to obtain nanosized platinum particles with a good distribution onto the graphitic surface. The morphology and structure of the obtained particles were investigated by scanning electron microscopy combined with energy dispersive X-Ray spectroscopy. The amount of deposited platinum was established using thermogravimetrical measurements. Cyclic voltammetry performed in 0.5 M H2SO4 solution was applied for determining the electrochemical surface area (ECSA) of the obtained electrodes.The functionalization degree of the CNF outer surface has a strong influence on the structure, distribution and amount of platinum particles. Moreover, the current densities, which were set for the deposition process influenced not only the particles size but also the platinum amount. Applying an oxygen plasma treatment of 80 W for 1800 s, the necessary degree of surface functionalization is achieved in order to deposit the catalyst particles. The best electrodes were prepared using a current density of 50 mA cm-2 during the deposition process that leads to a homogenous platinum distribution with particles size under 80 nm and ECSA over 6 cm2 KW - carbon nanofibers KW - platinum electrodeposition KW - electrocatalysts Y1 - 2016 U6 - https://doi.org/10.4028/www.scientific.net/SSP.254.153 IS - 254 SP - 153 EP - 158 ER - TY - JOUR A1 - Muntean, Roxana A1 - Rost, Ulrich A1 - Pascal, Dragos-Toader A1 - Marginean, Gabriela A1 - Vaszilcsin, Nicolae T1 - Determination of the Electrochemical Surface Area for CNF-Pt Electrocatalyst Using Cyclic Voltammetry JF - Chemical Bulletin of “Politehnica” University of Timisoara, Romania N2 - Carbon Nanofibers (CNF) are considered to be a promising catalyst support material due to their unique characteristics, excellent mechanical, electrical and structural properties, high surface area and nevertheless, good interaction with metallic catalyst particles. The possibility of preparing CNF decorated with platinum by an electrochemical method was tested, using a hexachloroplatinic bath solution. The experiments were carried out with the aid of a Potentiostat/Galvanostat Ivium Technologies Vertex, in a three – electrode cell. The aim of the present work was to determine the electrochemical surface area (ECSA) of the CNF-Pt catalysts in relation to the functionalization treatment of fibers, using an electrochemical method. ECSA for different functionalized CNF-Pt catalysts was determined by cyclic voltammetry in 0.5 M H2SO4 solution. The highest active surface of platinum was obtained for the samples with CNF functionalized by plasma treatment using 80 W for 1800 s. The obtained results correlate very well with the particles size and distribution of platinum, revealed by scanning electron microscopy (SEM) and the quantity of deposited platinum determined by thermo gravimetrical analysis (TGA) respectively. Cyclic voltammetry (CV) has been proven to be a suitable method for estimation of the ECSA of the electrocatalysts. KW - carbon nanofibers KW - platinum electrodeposition KW - electrochemical surface area Y1 - 2016 VL - 61 (75) IS - 2 SP - 44 EP - 48 ER - TY - CHAP A1 - Rost, Ulrich A1 - Rigou, Veronica A1 - Marginean, Gabriela A1 - Brodmann, Michael A1 - Brandl, Waltraut T1 - Oxygen Plasma Activated Carbon Nanofibres as Electrode Material for Proton Exchange Membrane Fuel Cells T2 - Konferenz: Junior Euromat 2014: The Major Event for Young Materials Scientists, 21.-25. Juli 2014 in Lausanne (Schweiz) N2 - To further increase platinum utilisation in PEM fuel cells CNFs are investigated as catalyst support material due to the CNF’s high specific surface area. Furthermore, CNFs provide suitable properties concerning corrosion resistance as well as electrical conductivity in contrast to conventional carbon supports. This work presents the results of an electrode preparation procedure based on O2 plasma activated CNFs. The plasma treatment leads to CNF dispersibility in alcohol/water for a spray coating process. Furthermore, O2 plasma activation enhances metal deposition on the CNF’s surface. Pulse plating procedure as well as wet chemical metal synthesis have been used for particle deposition. For pulse plating a potentiostat/galvanostat type MMates 510 AC from Materials Mates, Italy has been used. Electrode morphology has been determined in SEM type XL 30 ESEM from Philips, The Netherlands. Y1 - 2014 ER - TY - CHAP A1 - Muntean, Roxana A1 - Rost, Ulrich A1 - Marginean, Gabriela A1 - Vaszilcsin, Nicolae ED - Transilvania University of Brasov - Romania. Faculty of Materials Science and Engineering, T1 - Determination of the electrochemical surface area for CNTs-PT electro catalyst using cyclic voltammetry T2 - Konferenz: BraMat 2015, 9th International Conference on Materials Science & Engineering, March 5-7, 2015. Book of Abstracts N2 - Platinum is one of the most effective electro catalysts for PEMFCs (proton exchange membrane fuel cells), but because of its prohibitive price, the use of this metal in industrial purposes is limited. As a consequence, during last years, several materials have been investigated, in order to obtain an efficient catalyst for both ORR (oxygen reduction reaction) and HOR (hydrogen oxidation reaction), which can replace the expensive platinum but preserving the same properties: high electrical conductivity, structural stability and good corrosion resistance. Moreover, one of the most important parameters for catalyst materials is the electrochemical surface area (real surface area), which has a strong influence on the reaction rate and also on the current density. CNFs (carbon nanofibers) are considered to be a promising catalyst support material due to their unique characteristics, excellent mechanical, electrical and structural properties, high surface area and nevertheless, good interaction with platinum particles. The possibility of preparing CNFs decorated with platinum by electrochemical methods was tested, using a hexachloroplatinic solution bath. The experiments were carried out with the aid of a Potentiostat/Galvanostat MMate 510, in a three – electrode cell. The aim of the present work was to determine the electrochemical surface area of the CNFs – Pt catalysts, using an electrochemical method. The obtained results correlate very well with the particles size and distribution of platinum, analyzed by SEM (scanning electron microscopy) respectively with the quantity of deposited platinum determined by TG (thermo gravimetrical analyses). Cyclic voltammetry is a suitable method for estimation of the real surface area for catalyst particles. Y1 - 2015 SP - 170 PB - Transilvania University of Brasov - Romania CY - Brasov ER - TY - CHAP A1 - Rost, Ulrich A1 - Muntean, Roxana A1 - Podleschny, Pit Yannick A1 - Marginean, Gabriela A1 - Brodmann, Michael A1 - Şerban, Viorel-Aurel ED - Politehnica University of Timisoara, T1 - Investigation of the Influence of Graphitisation Degree of Carbon Nano Fibres Serving as Catalyst Support Material for Noble Metal Electro Catalysts on the Performance of PEM Fuel Cells T2 - Sixth International Conference on Advanced Materials and Structures. 16-17 October 2015, Timisoara, Romania N2 - In polymer electrolyte membrane fuel cells (PEMFC) noble metal nano particles are deposited on graphitic supports serving as electrocatalysts for devices with high power density. In this study anodes are analysed with low platinum loading of about 0.1 mg cm-2. These electrodes are prepared by carbon nano fibres (CNF) decorated with platinum nano particles. For electrode manufacturing two sorts of fibres, which are produced in an industrial scale, are used with different graphitisation degree and surface area. CNF layers are applied on commercially available graphitic substrate by spray coating which leads to a porous structure with high surface area. Subsequently, platinum deposition is achieved by pulsed electroplating for an improved platinum utilisation in PEMFC electrodes. Spray coating and platinum deposition are assisted by a previous oxygen plasma activation process. Prepared anode material is characterised by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction spectroscopy (XRD), X-ray fluorescence spectroscopy (XRF) and thermogravimetry (TGA). Electrochemical analyses (cyclic voltammetry and corrosion test) are carried out in 0.5 M sulphuric acid. The effect of graphitisation degree of carbon nano fibres on the performance of prepared electrodes is investigated in-situ in a PEM fuel cell test bench. Y1 - 2015 SP - 6 PB - Editura Politehnica CY - Timișoara ER - TY - CHAP A1 - Rost, Ulrich A1 - Muntean, Roxana A1 - Marginean, Gabriela A1 - Vaszilcsin, Nicolae A1 - Brodmann, Michael T1 - Effect of the Process Parameters for Oxygen Plasma Activation of Carbon Nanofibres on the Characteristics of Deposited Platinum Catalyst Nanoparticles T2 - Konferenz: The Annual World Conference on Carbon, 12.-17. Juli 2015 in Dresden N2 - In state of the art polymer electrolyte membrane fuel cells (PEMFC) rare and expensive platinum group metals (PGM) are used as catalyst material. Reduction of PGM in PEMFC electrodes is strongly required to reach cost targets for this technology. An optimal catalyst utilisation is achieved in the case of nano-structured particles supported on carbon material with a large specific surface area. In this study, graphitic material in form of carbon nanofibres (CNFs) is decorated with platinum (Pt) particles serving as catalyst material for PEMFC electrodes with low Pt loading. For electrode preparation CNFs have been previously activated by means of radio frequency induced oxygen plasma. This kind of treatment results in formation of functional groups on the CNF’s surface which directly influences the characteristics of subsequent Pt particle deposition. Different plasma parameters (plasma power, gas flow or exposure time) have to be set in order to achieve formation of oxygen containing functional groups (hydroxylic, carboxylic or carbonylic) on the CNF’s surface. In the frame of this experimental work, electrodes are investigated in respect of optimal morphology, microstructure as well as electrochemical properties. Therefore, samples were characterised by means of scanning electron microscopy combined with energy dispersive X-ray analysis, transmission electron microscopy, thermogravimetry, X-ray diffraction, X-ray fluorescence as well as polarisation measurements. Y1 - 2015 N1 - Die Konferenzbeiträge sind auf einem Datenträger an die Teilnehmer ausgehändigt worden. ER - TY - CHAP A1 - Rigou, Veronica A1 - Rost, Ulrich A1 - Marginean, Gabriela A1 - Brodmann, Michael A1 - Brandl, Waltraut T1 - Oxygen Plasma Activated Carbon Nanotubes as Electrode Material for Proton Exchange Membrane Fuel Cells T2 - Konferenz: "2nd International Conference on Materials for Energy", 12.-16. Mai 2013 in Karlsruhe N2 - Since the 1980’s, against the backdrop of global warming and the decline of conventional energy resources, low emission and renewable energy systems have gotten into the focus of politics as well as research and development. In order to decrease the emission of greenhouse gases Germany intents to generate 80% of its electrical energy from renewable and low emission sources by 2050. For low emission electricity generation hydrogen operated fuel cells are a potential solution. However, although fuel cell technology has been well known since the 19th century cost effective materials are needed to achieve a breakthrough in the market. Proton Exchange Membrane Fuel Cells with Carbon Nanotubes as Electrode Material At the Westphalian Energy Institute of the Wesphalian University of Applied Sciences one main focus is on the research of proton exchange membrane fuel cells (PEMFC). PEMFC membrane electrode assemblies (MEA) consist of a polymer membrane with electrolytic properties covered on both sides by a catalyst layer (CL) as well as a porous and electrical conductive gas diffusion layer (GDL). For PEMFC carbon nanotubes (CNT) have ideal properties as electrode material concerning electrical conductivity, oxidation resistance and media transport. CNTs are suitable for the use as catalyst support material within the CL due to their large surface in comparison to conventional carbon supports. Furthermore, oxygen plasma treated CNTs show electrochemical activity referred to hydrogen adsorption and desorption, which has been shown by cyclic voltammetry in 0.5 M sulfuric acid solution. According to the PEMFCs anode a GDL coated with oxygen plasma activated CNTs has promising properties to significantly reduce catalyst content (e.g. platinum) of the anodic CL. KW - Polymer-Elektrolytmembran-Brennstoffzelle KW - Kohlenstoff-Nanoröhre KW - Erneuerbare Energien Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:1010-opus4-7123 ER - TY - CHAP A1 - Rost, Ulrich A1 - Brandl, Waltraut A1 - Brodmann, Michael A1 - Marginean, Gabriela A1 - Rigou, Veronica T1 - Development of Membrane Electrode Assemblies Based on Oxygen Plasma Activated Carbon Nanotubes and their Application in a Novel Modular Test System with Hydraulic Compression T2 - Konferenz: 14th Ulm Electrochemical Talks (UECT), 23.-26.06.2014 in Ulm N2 - The membrane electrode assemblies (MEA) for polymer electrolyte membrane fuel cells (PEMFC) developed at the Westphalian Energy Institute are based on oxygen plasma activated carbon nanotubes (CNT) doped with platinum particles. For electrode preparation an ink is used containing the activated CNTs as well as hydrophobic and hydrophilic material in solved form. After this ink is sprayed onto a graphitic substrate platinum particles are deposited by pulse plating method, where the plasma activation enhances CNT dispersibility as well as platinum deposition. This materials mixture is structured in nanoscale with the aim to increase the catalyst particles’ specific surface. For low reactance at operation, homogeneous compression of the MEA’s layers is necessary within a PEMFC. A novel stack architecture for electrochemical cells, especially PEMFC as well as PEM electrolysers, has been developed in order to achieve ideal cell operation conditions. Single cells of such a stack are inserted into flexible slots that are surrounded by a hydraulic medium which is pressurised during operation in order to achieve an even compression and cooling of the stack’s cells. With this stack design it has been possible to construct a test facility for simultaneous characterisation of several MEA samples. As compression and temperature conditions of every single sample are the same, the effects of e.g. different electrode configurations can be investigated with the novel test system. Y1 - 2014 N1 - Veröffentlichung der Beiträge auf einem USB-Stick an die Teilnehmer. ER - TY - JOUR A1 - Ciubotariu, Costel-Relu A1 - Frunzaverde, Doina A1 - Marginean, Gabriela A1 - Şerban, Viorel-Aurel A1 - Birdeanu, Aurel-Valentin T1 - Optimization of the laser remelting process for HVOF-sprayed Stellite 6 wear resistant coatings JF - Optics & Laser Technology N2 - Cobalt base alloys are used in all industrial areas due to their excellent wear resistance. Several studies have shown that Stellite 6 coatings are suitable not only for protection against sliding wear, but also in case of exposure to impact loading. In this respect, a possible application is the protection of hydropower plant components affected by cavitation. The main problem in connection with Stellite 6 is the deposition procedure of the protective layers, both welding and thermal spraying techniques requesting special measures in order to prevent the brittleness of the coating. In this study, Stellite 6 layers were HVOF thermally sprayed on a martensitic 13-4 stainless steel substrate, as usually used for hydraulic machinery components. In order to improve the microstructure of the HVOF-sprayed coatings and their adhesion to the substrate, laser remelting was applied, using a TRUMPF Laser type HL 124P LCU and different working parameters. The microstructure of the coatings, obtained for various remelting conditions, was evaluated by light microscopy, showing the optimal value of the pulse power, which provided a homogenous Stellite 6 layer with good adhesion to the substrate. KW - Stellite 6 KW - HVOF-spraying KW - Laser remelting KW - Cavitation erosion KW - Coatings Y1 - 2016 VL - 77 SP - 98 EP - 103 ER - TY - CHAP A1 - Böhm, Leonard A1 - Thielker, Klaus A1 - Kazamer, Norbert A1 - Wirkert, Florian Josef A1 - Marginean, Gabriela A1 - Rost, Ulrich A1 - Apfel, Ulf-Peter A1 - Brodmann, Michael T1 - Electrodeposition of a Ni-Mo alloy Catalyst with Optimized Mo-Content for Hydrogen Evolution Reaction in AEM-Electrolysis T2 - WHEC-2022, 23rd World Hydrogen Energy Conference N2 - Various aqueous citrate electrolyte compositions for the Ni-Mo electrodeposition are explored in order to deposit Ni-Mo alloys with Mo-content ranging from 40 wt% to 65 wt% to find an alloy composition with superior catalytic activity towards the hydrogen evolution reaction (HER). The depositions were performed on copper substrates mounted onto a rotating disc electrode (RDE) and were investigated via scanning electron microscopy (SEM), X-ray fluorescence (XRF) and X-ray diffraction (XRD) methods as well as linear sweep voltammetry (LSV) and impedance spectroscopy. Kinetic parameters were calculated via Tafel analysis. Partial deposition current densities and current efficiencies were determined by correlating XRF measurements with gravimetric results. The variation of the electrolyte composition and deposition parameters enabled the deposition of alloys with Mo-content over the range of 40-65 wt%. An increase in Mo-content in deposited alloys was recorded with an increase in rotation speed of the RDE. Current efficiency of the deposition was in the magnitude of <1%, which is characteristic for the deposition of alloys with high Mo-content. The calculated kinetic parameters were used to determine the Mo-content with the highest catalytic activity for use in the HER. KW - Electrodeposition KW - Ni-Mo alloy Catalyst KW - AEM-Electrolysis Y1 - 2022 ER - TY - JOUR A1 - Rost, Ulrich A1 - Podleschny, Pit Yannick A1 - Schumacher, Marc A1 - Muntean, Roxana A1 - Pascal, Dragos-Toader A1 - Mutascu, Cristian A1 - Koziolek, J. A1 - Marginean, Gabriela A1 - Brodmann, Michael T1 - Long-term Stable Electrodes Based on Platinum Electrocatalysts Supported on Titanium Sintered Felt for the Use in PEM Fuel Cells JF - IOP conference series. Materials science and engineering Y1 - 2018 U6 - https://doi.org/10.1088/1757-899X/416/1/012013 SN - 1757-8981 IS - 416 SP - 012013 ER - TY - JOUR A1 - Kurumlu, Deniz A1 - Kazamer, Norbert A1 - Marginean, Gabriela A1 - Kiryc, Markus T1 - Comparative Study on the Thermal Performance of Cr-CrxOy and YSZ-CoNiCrAlY Coatings Exposed at 900 °C JF - Metal Coatings for Wear and Corrosion Applications KW - Thermal Performance Y1 - 2021 U6 - https://doi.org/https://doi.org/10.3390/ma14206040 VL - 6040 IS - 14/20 ER - TY - JOUR A1 - Muntean, Roxana A1 - Pascal, Dragos-Toader A1 - Rost, Ulrich A1 - Marginean, Gabriela A1 - Brodmann, Michael A1 - Vaszilcsin, Nicolae T1 - Synthesis and characterisation of platinum–cobalt–manganese ternary alloy catalysts supported on carbon nanofibers: An alternative catalyst for hydrogen evolution reaction JF - International Journal of Hydrogen Energy N2 - A systematic method for obtaining a novel electrode structure based on PtCoMn ternary alloy catalyst supported on graphitic carbon nanofibers (CNF) for hydrogen evolution reaction (HER) in acidic media is proposed. Ternary alloy nanoparticles (Co0.6Mn0.4 Pt), with a mean crystallite diameter under 10 nm, were electrodeposited onto a graphitic support material using a two-step pulsed deposition technique. Initially, a surface functionalisation of the carbon nanofibers is performed with the aid of oxygen plasma. Subsequently, a short galvanostatic pulse electrodeposition technique is applied. It has been demonstrated that, if pulsing current is employed, compositionally controlled PtCoMn catalysts can be achieved. Variations of metal concentration ratios in the electrolyte and main deposition parameters, such as current density and pulse shape, led to electrodes with relevant catalytic activity towards HER. The samples were further characterised using several physico-chemical methods to reveal their morphology, structure, chemical and electrochemical properties. X-ray diffraction confirms the PtCoMn alloy formation on the graphitic support and energy dispersive X-ray spectroscopy highlights the presence of the three metallic components from the alloy structure. The preliminary tests regarding the electrocatalytic activity of the developed electrodes display promising results compared to commercial Pt/C catalysts. The PtCoMn/CNF electrode exhibits a decrease in hydrogen evolution overpotential of about 250 mV at 40 mA cm−2 in acidic solution (0.5 M H2SO4) when compared to similar platinum based electrodes (Pt/CNF) and a Tafel slope of around 120 mV dec−1, indicating that HER takes place under the Volmer-Heyrovsky mechanism. KW - PtCoMn KW - Ternary alloy catalyst preparation KW - PEM water electrolysis KW - Hydrogen evolution reaction Y1 - 2020 U6 - https://doi.org/10.1016/j.ijhydene.2020.02.041 SN - 0360-3199 ER - TY - CHAP A1 - Böhm, Leonard A1 - Kazamer, Norbert A1 - Holtkotte, Lisa A1 - Näther, Johannes A1 - Rost, Ulrich A1 - Underberg, Martin A1 - Marginean, Gabriela A1 - Hülser, Tim A1 - Brodmann, Michael A1 - Köster, Frank T1 - Pulsed electrodeposition of iridium catalyst nanoparticles on titanium suboxide supports for application in PEM electrolysis T2 - Konferenz: "8th International Conference on Advanced Materials and Structures - AMS 2020", 7.-9. Oktober 2020 in Timișoara (Rumänien) Y1 - 2020 ER - TY - JOUR A1 - Podleschny, Pit Yannick A1 - Rost, Ulrich A1 - Muntean, Roxana A1 - Marginean, Gabriela A1 - Heinzel, Angelika A1 - Peinecke, Volker A1 - Radev, Ivan A1 - Muhler, Martin A1 - Brodmann, Michael T1 - Investigation of Carbon Nanofiber‐supported Electrocatalysts with Ultra‐low Platinum Loading for the Use in PEM Fuel Cells JF - Fuel Cells. From fundamentals to systems Y1 - 2018 U6 - https://doi.org/10.1002/fuce.201700220 SN - 1615-6854 VL - 18 IS - 5 SP - 586 EP - 593 ER - TY - CHAP A1 - Podleschny, Pit Yannick A1 - Rost, Ulrich A1 - Muntean, Roxana A1 - Marginean, Gabriela A1 - Brodmann, Michael A1 - Radev, Ivan A1 - Peinecke, Volker A1 - Heinzel, Angelika T1 - Investigation of Carbon Nanofiber (CNF) Supported Platinum Electrocatalysts for the Use in PEM Fuel Cells T2 - Konferenz: 6th European PEFC & Electrolyser Forum, 4.-7. Juli 2017 in Luzern, Schweiz Y1 - 2017 ER - TY - CHAP A1 - Podleschny, Pit Yannick A1 - Marginean, Gabriela A1 - Muntean, Roxana A1 - Rost, Ulrich A1 - Brodmann, Michael T1 - Influence of Catalyst Support Composition in PEM Fuel Cell Electrodes Utilizing Plasma Treated Graphene Related Material Decorated with Platinum Nanoparticles T2 - Konferenz: 7. NRW Nano-Konferenz, 7.-8. Dezember 2016 in Münster N2 - This work deals with the preparation and investigation of PEM fuel cell electrodes, which are obtained using graphene related material (GRM) serving as catalyst support for platinum nanoparticles. Applied GRM are used for the preparation of suspensions in four distinct mixing ratios. Two sorts of GRM have been investigated: carbon nanofibers (CNF) and graphene oxide (GO). Utilized CNFs provide a superior graphitization degree of about 100%, which leads to both high corrosion resistance and low ohmic resistance in PEM fuel cells. For electrode preparation a GRM containing layer serving as catalyst support is applied onto a gas diffusion layer (GDL). Prior to GRM suspension and deposition onto a GDL, the graphene structures are functionalized by plasma treatment. Due to this step, an improved hydrophilic behavior for facilitating suspension preparation is achieved. In addition, a subsequent platinum nanoparticle deposition by pulsed electrodeposition process is optimized. Y1 - 2016 ER - TY - CHAP A1 - Rost, Ulrich A1 - Podleschny, Pit Yannick A1 - Schumacher, Marc A1 - Muntean, Roxana A1 - Pascal, Dragos-Toader A1 - Mutascu, Cristian A1 - Koziolek, J. A1 - Marginean, Gabriela A1 - Brodmann, Michael T1 - Long-term Stable Electrodes Based on Platinum Electrocatalysts Supported on Titanium Sintered Felt for the Use in PEM Fuel Cells T2 - Konferenz: 7th International Conference on Advanced Materials and Structures (AMS 2018), 28.-31. März 2018 in Timisoara (Rumänien) Y1 - 2018 ER - TY - JOUR A1 - Muntean, Roxana A1 - Pascal, Dragos-Toader A1 - Rost, Ulrich A1 - Marginean, Gabriela A1 - Brodmann, Michael A1 - Vaszilcsin, Nicolae T1 - Synthesis and characterisation of platinum–cobalt–manganese ternary alloy catalysts supported on carbon nanofibers: An alternative catalyst for hydrogen evolution reaction JF - International Journal of Hydrogen Energy Y1 - 2020 U6 - https://doi.org/10.1016/j.ijhydene.2020.02.041 VL - 45 IS - 49 SP - 26217 EP - 26225 ER - TY - CHAP A1 - Muntean, Roxana A1 - Pascal, Dragos-Toader A1 - Rost, Ulrich A1 - Marginean, Gabriela A1 - Vaszilcsin, Nicolae A1 - Brodmann, Michael T1 - PtCoMn ternary alloy supported catalysts for hydrogen evolution reaction T2 - Konferenz: 10th International Conference on Hydrogen Production, 15.-17. Mai 2019 in Cluj-Napoca, Rumänien Y1 - 2019 ER - TY - JOUR A1 - Rost, Ulrich A1 - Muntean, Roxana A1 - Pascal, Dragos-Toader A1 - Podleschny, Pit Yannick A1 - Schumacher, Marc A1 - Marginean, Gabriela T1 - Studies on Pulse Electrodeposition of Pt-Ni binary Alloy For Electrochemical Cell Applications JF - IOP conference series. Materials science and engineering Y1 - 2018 U6 - https://doi.org/10.1088/1757-899X/416/1/012004 SN - 1757-8981 IS - 416 SP - 012004 ER - TY - JOUR A1 - Utu, Ion-Dragos A1 - Anghel (Petculescu), Iasmina-Madalina A1 - Hulka, Iosif A1 - Marginean, Gabriela T1 - Design, Manufacturing, Microstructure, and Surface Properties of Brazed Co-Based Composite Coatings Reinforced with Tungsten Carbide Particles JF - Crystals MDPI N2 - Brazing is a joining process that involves melting a filler metal and flowing it into the joint between two closely fitting parts. While brazing is primarily used for joining metals, it can also be adapted for certain coating deposition applications. The present study investigates the microstructure and corrosion behavior and sliding wear resistance of WC (Tungsten Carbide)-CoCr-Ni reinforced Co-based composite coatings deposited onto the surface of AISI 904L stainless steel using a vacuum brazing method. The primary objective of this experimental work was to evaluate the influence of WC-based particles added to the microstructure and the properties of the brazed Co composite coating. The focus was on enhancing the sliding wear resistance of the coatings while ensuring that their corrosion resistance in chloride media was not adversely affected. The morphology and microstructure of the composite coatings were investigated using scanning electron microscopy (SEM) and phase identification by X-ray diffraction (XRD). The SEM analysis revealed in the coating the presence of intermetallic compounds and carbides, which increase the hardness of the material. The sliding wear resistance was assessed using the pin-on-disk method, and the corrosion properties were determined using electrochemical measurements. The results obtained showed that as the WC particle ratio in the Co-based composite coating increased, the mechanical properties improved, the alloy became harder, and the tribological properties were improved. The evaluation of the electrochemical tests revealed no significant alterations of the manufactured composite in comparison with the Co-based alloys. In all cases, the corrosion behavior was better compared with that of the stainless-steel substrate. KW - co-based coatings KW - brazing KW - wear resistance KW - corrosion behavior Y1 - 2024 U6 - https://doi.org/10.3390/cryst14060576 VL - 14 (2024) IS - 6, Aufsatz 576 ER - TY - JOUR A1 - Frunzaverde, Doina A1 - Cojocaru, Vasile A1 - Bacescu, Nicoleta A1 - Ciubotariu, Costel-Relu A1 - Miclosina, Calin-Octavian A1 - Turiac, Raul-Rusalin A1 - Marginean, Gabriela T1 - The Influence of the Layer Height and the Filament Color on the Dimensional Accuracy and the Tensile Strength of FDM-Printed PLA Specimens JF - Polymers MDPI N2 - Among the FDM process variables, one of the less addressed in previous research is the filament color. Moreover, if not explicitly targeted, the filament color is usually not even mentioned. Aiming to point out if, and to what extent, the color of the PLA filaments influences the dimensional precision and the mechanical strength of FDM prints, the authors of the present research carried out experiments on tensile specimens. The variable parameters were the layer height (0.05 mm, 0.10 mm, 0.15 mm, 0.20 mm) and the material color (natural, black, red, grey). The experimental results clearly showed that the filament color is an influential factor for the dimensional accuracy as well as for the tensile strength of the FDM printed PLA parts. Moreover, the two way ANOVA test performed revealed that the strongest effect on the tensile strength was exerted by the PLA color (� 2 = 97.3%), followed by the layer height (� 2 = 85.5%) and the interaction between the PLA color and the layer height (� 2 = 80.0%). Under the same printing conditions, the best dimensional accuracy was ensured by the black PLA (0.17% width deviations, respectively 5.48% height deviations), whilst the grey PLA showed the highest ultimate tensile strength values (between 57.10 MPa and 59.82 MPa). KW - fused deposition modeling (FDM); fused filament fabrication (FFF); polylactic acid (PLA); layer height; layer thickness; filament color; PLA color; dimensional accuracy; tensile strength Y1 - 2023 U6 - https://doi.org/10.3390/polym15102377 VL - 2023 IS - 15 / 10 SP - 2377 ER - TY - JOUR A1 - Frunzaverde, Doina A1 - Cojocaru, Vasile A1 - Ciubotariu, Costel-Relu A1 - Miclosina, Calin-Octavian A1 - Ardeljan, Deian Dorel A1 - Ignat, Emil Florin A1 - Marginean, Gabriela T1 - The Influence of the Printing Temperature and the Filament Color on the Dimensional Accuracy, Tensile Strength, and Friction Performance of FFF-Printed PLA Specimens JF - Polymers MDPI N2 - The printing variable least addressed in previous research aiming to reveal the effect of the FFF process parameters on the printed PLA part’s quality and properties is the filament color. Moreover, the color of the PLA, as well as its manufacturer, are rarely mentioned when the experimental conditions for the printing of the samples are described, although current existing data reveal that their influence on the final characteristics of the print should not be neglected. In order to point out the importance of this influential parameter, a natural and a black-colored PLA filament, produced by the same manufacturer, were selected. The dimensional accuracy, tensile strength, and friction properties of the samples were analyzed and compared for printing temperatures ranging from 200 � C up to 240 � C. The experimental results clearly showed different characteristics depending on the polymer color of samples printed under the same conditions. Therefore, the optimization of the FFF process parameters for the 3D-printing of PLA should always start with the proper selection of the type of the PLA material, regarding both its color and the fabricant. KW - additive manufacturing KW - polylactic acid (PLA) KW - fused filament fabrication (FFF) KW - fused deposition modeling (FDM) KW - printing temperature KW - filament color KW - dimensional accuracy KW - tensile strength KW - friction performance; wear Y1 - 2022 U6 - https://doi.org/10.3390/polym14101978 VL - 2022 IS - 14 SP - 1978 ER - TY - JOUR A1 - Kazamer, Norbert A1 - Muntean, Roxana A1 - Utu, Ion-Dragos A1 - Marginean, Gabriela T1 - Considerations on the Wear Behavior of Vacuum-Remelted ZrO2-Reinforced Self-Fluxing Ni-Based Thermally Sprayed Alloys JF - Materials MDPI N2 - Without proper post-processing (often using flame, furnace, laser remelting, and induction) or reinforcements’ addition, Ni-based flame-sprayed coatings generally manifest moderate adhesion to the substrate, high porosity, unmelted particles, undesirable oxides, or weak wear resistance and mechanical properties. The current research aimed to investigate the addition of ZrO2 as reinforcement to the self-fluxing alloy coatings. Mechanically mixed NiCrBSi-ZrO2 powders were thermally sprayed onto an industrially relevant high-grade steel. After thermal spraying, the samples were differently post-processed with a flame gun and with a vacuum furnace, respectively. Scanning electron microscopy showed a porosity reduction for the vacuum-heat-treated samples compared to that of the flame-post-processed ones. X-ray diffraction measurements showed differences in the main peaks of the patterns for the thermal processed samples compared to the as-sprayed ones, these having a direct influence on the mechanical behavior of the coatings. Although a slight microhardness decrease was observed in the case of vacuum-remelted samples, the overall low porosity and the phase differences helped the coating to perform better during wear-resistance testing, realized using a ball-on-disk arrangement, compared to the as-sprayed reference samples. KW - self-fluxing; ZrO2; NiCrBSi; vacuum post-treatment; thermal spraying Y1 - 2023 U6 - https://doi.org/10.3390/ma16145183 VL - 2023 IS - 16 / 14 SP - 5183 ER - TY - JOUR A1 - Schwanekamp, Tobias A1 - Marginean, Gabriela A1 - Reuber, Martin A1 - Ostendorf, Andreas T1 - Impact of cobalt content and grain growth inhibitors in laser-based powder bed fusion of WC-Co JF - International Journal of Refractory Metals and Hard Materials N2 - Processing of tungsten carbide‑cobalt (WC-Co) by laser-based powder bed fusion (PBF-LB) can result in characteristic microstructure defects such as cracks, pores, undesired phases and tungsten carbide (WC) grain growth, due to the heterogeneous energy input and the high thermal gradients. Besides the processing conditions, the material properties are affected by the initial powder characteristics. In this paper, the impact of powder composition on microstructure, phase formation and mechanical properties in PBF-LB of WC-Co is studied. Powders with different cobalt contents from 12 wt.-% to 25 wt.-% are tested under variation of the laser parameters. Furthermore, the impact of vanadium carbide (VC) and chromium (Cr) additives is investigated. Both are known as grain growth inhibitors for conventional sintering processes. The experiments are conducted at a pre-heating temperature of around 800 ◦C to prevent crack formation in the samples. Increasing laser energy input reduces porosity but leads to severe embrittlement for low cobalt content and to abnormal WC grain growth for high cobalt content. It is found that interparticular porosity at low laser energy is more severe for low cobalt content due to poor wetting of the liquid phase. Maximum bending strength of σB > 1200 MPa and Vickers hardness of approx. 1000 HV3 can be measured for samples generated from WC-Co 83/17 powder with medium laser energy input. The addition of V and Cr leads to increased formation of additional phases such as Co3W3C, Co3V and Cr23C6 and to increased lateral and multi-laminar growth of the WC grains. In contrast to conventional sintering, a grain growth inhibiting effect of V and Cr in the laser molten microstructure is not achieved. Y1 - 2022 U6 - https://doi.org/10.1016/j.ijrmhm.2022.105814 SP - 105814 ER - TY - JOUR A1 - Utu, Ion-Dragos A1 - Marginean, Gabriela A1 - Hulka, Iosif A1 - Şerban, Viorel-Aurel A1 - Cristea, Dan T1 - Properties of the thermally sprayed Al2O3–TiO2 coatings deposited on titanium substrate JF - International Journal of Refractory Metals and Hard Materials N2 - Based on the fact that titanium and titanium alloys have poor fretting fatigue resistance and poor tribological properties, it is necessary to apply some surface engineering methods in order to increase the exploitation characteristics of these materials. One may either implement some surface treatment technologies or even deposit overlay coatings by thermal spraying. The present study is focused on the achieved properties of the ceramic coatings (Al2O3 + 13 wt.% TiO2) deposited onto a titanium substrate using high velocity oxygen fuel (HVOF) and plasma spraying (APS) respectively. The effect of the deposition method on the microstructure, phase constituents, and mechanical properties of the ceramic coatings was investigated by means of scanning electron microscopy (SEM), X-ray diffraction technique (XRD) and nanoindentation tests. The sliding wear performances of the Al2O3–TiO2 coatings were tested using a pin on disk wear tester. KW - Titanium KW - Al2O3–TiO2 coatings KW - Nanoindentation Y1 - 2015 VL - 51 SP - 118 EP - 123 ER - TY - JOUR A1 - Ciubotariu, Costel-Relu A1 - Secosan, Evelina A1 - Marginean, Gabriela A1 - Frunzaverde, Doina A1 - Campian, Viorel Constantin T1 - Experimental Study Regarding the Cavitation and Corrosion Resistance of Stellite 6 and Self-Fluxing Remelted Coatings JF - Strojniški vestnik - Journal of Mechanical Engineering N2 - This paper aims to compare cobalt-based (type Stellite 6) and nickel-based self-fluxing alloys (type NiCrBSiMo) regarding both their cavitation erosion resistance and corrosion resistance. The two types of protective layers were thermally sprayed onto a substrate of martensitic stainless steel. In order to improve the layers' characteristics and their metallurgical bonding to the substrate, the Stellite 6 coating was laser remelted, while the NiCrBSiMo coating was treated by flame fusion. The cavitation erosion resistance of the two materials was evaluated by measurements of the mean depth of erosion developed during a testing period of 165 minutes, using a 20 kHz ultrasonic vibrator at a peak-to-peak amplitude of 50 μm. In addition, the corrosion resistance of the layers was assessed by potentiodynamic corrosion tests carried out in H2SO4 + NaCl solution at room temperature, using calomel as reference electrode. In order to highlight the differences regarding the behaviour of the two protective materials, the authors also carried out microstructural investigations of the layers before and after exposure to cavitation and corrosion. The investigations showed that both types of layers can provide improved protection of the martensitic stainless steel substrate against cavitation, whilst the NiCrBSiMo coating additionally confers significantly increased resistance to corrosion. KW - Cavitation KW - Corrosion KW - Laser remelting KW - Self-fluxing alloys KW - Stellite 6 Y1 - 2016 VL - 62 IS - 3 SP - 154 EP - 162 ER - TY - JOUR A1 - Spunei, Elisabeta A1 - Frumusanu, Natalita-Mihaela A1 - Muntean, Roxana A1 - Marginean, Gabriela T1 - Impact of COVID-19 Pandemic on the Educational-Instructional Process of the Students from Technical Faculties JF - Sustainability MDPI N2 - Even though we live in a period when the word digitization is prevalent in many social areas, the COVID-19 pandemic has divided mankind into two main categories: some people have seen this crisis as an opportunity to move the activities online and, furthermore, to accelerate digitization in as many areas as possible, while others have been reluctant, keeping their preferences for face-to-face activities. The current work presents the results of an analysis on 249 students from 11 engineering faculties. The study aims to identify the impact of the COVID-19 pandemic on students’ educational experiences when switching from face-to-face to online education during a public health emergency or COVID 19-related state of alert. The overall conclusion was that, although the pandemic has brought adverse consequences on the health and life quality of many people, the challenges that humankind has been subjected to have led to personal and professional development and have opened up new perspectives for carrying out the everyday activities. KW - education KW - skills KW - competences KW - pandemic KW - online or face-to-face Y1 - 2022 U6 - https://doi.org/10.3390/su14148586 VL - 2022 IS - 14 SP - 8586 ER - TY - JOUR A1 - Ciubotariu, Costel-Relu A1 - Frunzaverde, Doina A1 - Marginean, Gabriela T1 - Investigations of Cavitation Erosion and Corrosion Behavior of Flame-Sprayed NiCrBSi/WC-12Co Composite Coatings JF - Materials MDPI N2 - Flame-sprayed NiCrBSi/WC-12Co composite coatings were deposited in different ratios on the surface of stainless steel. Oxyacetylene flame remelting treatment was applied to surfaces for refinement of the morphology of the layers and improvement of the coating/substrate adhesion. The performance of the coated specimens to cavitation erosion and electrochemical corrosion was evaluated by an ultrasonic vibratory method and, respectively, by polarization measurements. The microstructure was investigated by means of scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDX). The obtained results demonstrated that the addition of 15 wt.% WC-12Co to the self-fluxing alloy improves the resistance to cavitation erosion (the terminal erosion rate (Vs) decreased with 15% related to that of the NiCrBSi coating) without influencing the good corrosion resistance in NaCl solution. However, a further increase in WC-Co content led to a deterioration of these coating properties (the Vs has doubled related to that of the NiCrBSi coating). Moreover, the corrosion behavior of the latter composite coating was negatively influenced, a fact confirmed by increased values for the corrosion current density (icorr). Based on the achieved experimental results, one may summarize that NiCrBSi/WC-Co composite coatings are able to increase the life cycle of expensive, high-performance components exposed to severe cavitation conditions. KW - corrosion KW - self-fluxing alloys KW - NiCrBSi KW - WC-12Co KW - cavitation KW - hard metals Y1 - 2022 U6 - https://doi.org/10.3390/ma15082943 VL - 2022 IS - 15 SP - 2943 ER - TY - JOUR A1 - Utu, Ion-Dragos A1 - Hulka, Iosif A1 - Kazamer, Norbert A1 - Constantin, Albert Titus A1 - Marginean, Gabriela T1 - Hot-Corrosion and Particle Erosion Resistance of Co-Based Brazed Alloy Coatings JF - Crystals N2 - Tape brazing constitutes a cost-effective alternative surface protection technology for complex-shaped surfaces. The study explores the characteristics of high-temperature brazed coatings using a cobalt-based powder deposited on a stainless-steel substrate in order to protect parts subjected to hot temperatures in a wear-exposed environment. Microstructural imaging corroborated with x-ray diffraction analysis showed a complex phased structure consisting of intermetallic Cr-Ni, C-Co-W Laves type, and chromium carbide phases. The surface properties of the coatings, targeting hot corrosion behavior, erosion, wear resistance, and microhardness, were evaluated. The high-temperature corrosion test was performed for 100 h at 750 � C in a salt mixture consisting of 25 wt.% NaCl + 75 wt.% Na2SO4. The degree of corrosion attack was closely connected with the exposure temperature, and the degradation of the material corresponding to the mechanisms of low-temperature hot corrosion. The erosion tests were carried out using alumina particles at a 90� impingement angle. The results, correlated with the microhardness measurements, have shown that Co-based coatings exhibited approximately 40% lower material loss compared to that of the steel substrate. KW - co-based alloys KW - hot corrosion KW - solid particle erosion KW - microstructure KW - brazing Y1 - 2022 U6 - https://doi.org/10.3390/cryst12060762 VL - 2022 IS - 12 SP - 762 PB - MDPI ER - TY - JOUR A1 - Eßler, Julian A1 - Woelk, Dino Horst A1 - Utu, Ion-Dragos A1 - Marginean, Gabriela T1 - Influence of the powder feed rate on the properties of HVOF sprayed WC-based cermet coatings JF - Materials Today: Proceedings N2 - In this study, the characteristics of HVOF sprayed WC/Co-Cr and WC/Cr3C2/Ni coatings were investigated in correlation with the variation of the powder feed rate. For this purpose, the mass flow was adjusted to four different levels. The other process parameters were all kept constant. The morphological and mechanical properties as well as the electrochemical corrosion behaviour were investigated and associated with the achieved microstructure. Both scanning electron microscopy and confocal laser scanning microscopical images of the cross sections demonstrated a good correlation between the selected powder feed rate and the degree of internal porosity produced, which can be attributed to the deposition process. The coatings which fulfilled the requirements of the pre-qualification step were selected for further hardness measurements, tribological tests and electrochemical corrosion measurements in a 3.5 wt% NaCl aqueous solution. It was found that the powder feed rate strongly influenced the characteristics of the HVOF-sprayed cermet coatings. The tendency to crack formation, especially at the interface coating/substrate, was lower for the samples coated with a lower mass flow rate. These studies have shown that the applied powder feed rates had an important influence on the coatings microstructure and implicitly on the sliding wear behavior respectively on the electrochemical corrosion resistance of the investigated cermet coatings. KW - Powder feed rate HVOF Cermet Wear Corrosion Y1 - 2022 U6 - https://doi.org/10.1016/j.matpr.2022.11.120 VL - 2023 IS - 78 SP - 227 EP - 234 ER - TY - JOUR A1 - Brand, Marco A1 - Utu, Ion-Dragos A1 - Sirbu, Nicusor-Alin A1 - Perianu, Ion-Aurel A1 - Predu, Denis Andrei A1 - Marginean, Gabriela T1 - Microstructural Characteristics of Graded Ni-Fe Coatings Fabricated Through DED-L JF - Materials (Special Issue Advanced Coating Research for Metal Surface Protection) N2 - Directed Energy Deposition-Laser (DED-L) enables high-performance coatings through melting and successive powder deposition. Its compositional flexibility suits functionally graded layers that enhance corrosion and wear resistance. This study aimed to improve parameters for producing dense, defect-free, graded Ni- and Fe-based coatings by varying the scanning speed and deposition strategy (monodirectional versus bidirectional, with/without layer rotation), while keeping the power and hatch distance constant. Laser and electron microscopy were used to link parameters to porosity and uniformity. Optimal settings minimized pores, improved interlayer bonding and preserved geometry; inadequate parameters yielded porous, irregular deposits. A bidirectional path with 90° rotation appeared best. Ongoing research activities are needed to assess its properties. Highlights What are the main findings? - Bidirectional samples show fewer pores than samples with monodirectional movement. - Increasing the scanning speed leads to lower porosity (bidirectional scanning mode with 90° layer rotation). - Bidirectional deposition with 90° layer rotation exhibits best quality What are the implications of the main findings? - Systematic study of scanning speed and deposition strategy. - Practical guidance for process improvement of graded metal coatings; properties under evaluation. - Functionally graded Ni-Fe coatings fabricated by DED-L with tailored microstructures. KW - parameter study KW - directed energy deposition-laser KW - functionally graded materials KW - deposition strategy KW - powder processing KW - surface protection Y1 - 2025 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:1010-opus4-49138 SN - 1996-1944 VL - 2026 IS - 19 (2) PB - MDPI ER - TY - JOUR A1 - Ardeljan, Deian Dorel A1 - Frunzaverde, Doina A1 - Cojocaru, Vasile A1 - Turiac, Raul-Rusalin A1 - Bacescu, Nicoleta A1 - Ciubotariu, Costel-Relu A1 - Marginean, Gabriela T1 - The Impact of Elevated Printing Speeds and Filament Color on the Dimensional Precision and Tensile Properties of FDM-Printed PLA Specimens JF - Polymers N2 - This study examines the effect of elevated printing speeds (100–600 mm/s) on the dimensional accuracy and tensile strength of PLA components fabricated via fused deposition modeling (FDM). To isolate the influence of printing speed, all other parameters were kept constant, and two filament variants—natural (unpigmented) and black PLA—were analyzed. ISO 527-2 type 1A specimens were produced and tested for dimensional deviations and ultimate tensile strength (UTS). The results indicate that printing speed has a marked impact on both geometric precision and mechanical performance. The optimal speed of 300 mm/s provided the best compromise between dimensional accuracy and tensile strength for both filaments. At speeds below 300 mm/s, under-extrusion caused weak layer bonding and air gaps, while speeds above 300 mm/s led to over-extrusion and structural defects due to thermal stress and rapid cooling. Black PLA yielded better dimensional accuracy at higher speeds, with cross-sectional deviations between 2.76% and 5.33%, while natural PLA showed larger deviations of up to 8.63%. However, natural PLA exhibited superior tensile strength, reaching up to 46.59 MPa, with black PLA showing up to 13.16% lower UTS values. The findings emphasize the importance of speed tuning and material selection for achieving high-quality, reliable, and efficient FDM prints. KW - additive manufacturing KW - polylactic acid (PLA) KW - fused filament fabrication (FFF) KW - fused deposition modeling (FDM) KW - printing speed KW - filament color KW - dimensional accuracy KW - ultimate tensile strength (UTS) Y1 - 2025 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:1010-opus4-48255 VL - 2025 (Special Issue Mechanical Behaviour of Polymeric-Based Systems Used in Engineering Applications, 2nd Edition) IS - 17(15) PB - MDPI ER - TY - JOUR A1 - Cojocaru, Vasile A1 - Turiac, Raul-Rusalin A1 - Frunzaverde, Doina A1 - Trisca, Gelu A1 - Bacescu, Nicoleta A1 - Marginean, Gabriela T1 - Effect of the Printing Scenario on the Dimensional Accuracy and the Tensile Strength of Different Colored PLA Specimens Produced by Fused Deposition Modeling JF - Applied Sciences N2 - Dimensional accuracy and mechanical properties of components printed by fused deposition modeling (FDM) are influenced by several process parameters. In this paper, the authors targeted the effect of the printing scenario and the PLA (polylactic acid) color on parts’ quality. Three scenarios were analyzed: individually printing, simultaneously printing of three, respective five specimens of natural (transparent), red, grey, and black PLA. The temperature variations of successive deposited layers were recorded for the black PLA. The dimensional accuracy of tensile specimens was evaluated, tensile tests were performed, and the results were correlated with the mesostructure of the prints. The effect of the independent variables on the measured parameters was analyzed by ANOVA. The experiments revealed differences for the same printing scenario regarding cross-section area (up to 5.71%) and tensile strength (up to 10.45%) determined by the material color. The number of specimens printed simultaneously and the position of the pecimens on the build plate were found to influence too, but less than the color. Thus, increasing from one to five the number of specimens printed at a time altered both the dimensional accuracy (up to 3.93% increase of the cross-section area) and the tensile strength (up to 3.63% reduction). KW - fused deposition modeling (FDM) KW - polylactic acid (PLA) KW - printing scenario KW - filament color KW - dimensional accuracy KW - tensile strength (UTS) Y1 - 2024 U6 - https://doi.org/10.3390/app14177642 VL - 14 (2024) IS - 17, Artikel 7642 ER - TY - JOUR A1 - Brand, Marco A1 - Moeini, Ghazal A1 - Marginean, Gabriela T1 - Corrosion behavior of 316L additively produced by Directed Energy Deposition-Arc JF - Materials Today: Proceedings N2 - Among all additive manufacturing processes, Directed Energy Deposition-Arc (DED-Arc) shows significantly shorter production times and is particularly suitable for large-volume components of simple to medium complexity. To exploit the full potential of this process, the microstructural, mechanical and corrosion behavior have to be studied. High stickout distances lead to a large offset, which leads to an instable electric arc and thus defects such as lack of fusion. Since corrosion preferentially occurs at such defects, the main objective of this work is to investigate the influence of the stickout distance on the corrosion behavior and microstructure of stainless steel manufactured by DED-Arc. Within the heterogenous structure of the manufactured samples lack of fusion defects were detected. The quantity of such defects was reduced by applying a shorter stickout distance. The corrosion behavior of the additively manufactured specimens was investigated by means of potentiodynamic polarization measurements. The semi-logarithmic current density potential curves showed a similar course and thus similar corrosion resistance like that of the conventionally forged sample. The polarization curve of the reference material shows numerous current peaks, both in the anodic and cathodic regions. This metastable behavior is induced by the presence of manganese sulfides. On the sample surface a local attack by pitting corrosion was identified. KW - additive manufacturing KW - directed energy deposition-arc KW - 316L stainless steel KW - corrosion behavior KW - electrochemical corrosion Y1 - 2023 U6 - https://doi.org/10.1016/j.matpr.2022.11.194 VL - 2023 IS - 78 SP - 242 EP - 250 ER - TY - JOUR A1 - Brand, Marco A1 - Goßling, Mareen A1 - Utu, Ion-Dragos A1 - Marginean, Gabriela T1 - Comparative Performance of Ni- and Fe-Based Mixed Alloy Brazed Coatings via Laser Remelting JF - Lubricants (Special Issue Analysis, Evaluation and Diagnosis of Tribological Phenomena in Machining Processes) N2 - Traditionally, repairing coated substrates requires completely removing damaged, wear-resistant layers before recoating. This process leads to high costs, extended downtime, and material waste. Flexible brazing tapes, which are composed of alloy powder and an organic binder, offer an alternative to full coating removal for targeted repairs. Despite this, the process of vacuum brazing these tapes may lead to the formation of defects, including pores caused by trapped gases or residual binder, which compromise coating durability and corrosion resistance. This study focuses on the utilization of laser remelting as a method for post-processing nickel- and iron-based mixed alloy brazing tapes, with the aim of improving the integrity of the coating. Surface quality was assessed via microscopy and microhardness testing by systematically varying laser power, scanning speed, and hatch distance. Among the parameters studied, the most suitable laser parameter combination was found to be 350 W laser power, 250 mm/s scanning speed, and a hatch distance of 0.02 mm. These parameters yielded crack- and pore-free coatings with a remelting depth of 160.3 ± 17.2 µm and a microhardness of 701 ± 23 HV1, which is an 85% increase over as-brazed samples. Wear testing revealed a reduced coefficient of friction, and electrochemical corrosion tests showed lower corrosion current density and enhanced repassivation behavior in remelted coatings. These improvements demonstrate that laser remelting significantly enhances the microstructure, hardness, wear resistance, and corrosion performance of brazed coatings, providing an effective method for localized repair while minimizing material consumption and processing duration. KW - brazing tapes KW - sliding wear resistance KW - reuse KW - repair KW - laser surface refining KW - remelting KW - corrosion protection Y1 - 2026 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:1010-opus4-49343 VL - 2026 IS - 14 (4) PB - MDPI ER -