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Wiener Neustadt, Austria

Greul T.,Johannes Kepler University | Greul T.,Voestalpine AG | Gerdenitsch J.,Voestalpine AG | Commenda C.,Voestalpine AG | And 5 more authors.
Surface and Coatings Technology | Year: 2014

Electron backscatter diffraction (EBSD) measurements show epitaxial electrochemical deposition of zinc on non-deformed and contrariwise random growth on deformed steel grains. Therefore, electrochemical investigations on the differences of zinc electrodeposition on electropolished respectively on temper rolled low carbon steel sheet of the same substrate are studied. These measurements show great differences in ECN (electrochemical noise) investigations and the 1st cycle of a CV (cyclic voltammetry) only. It is found, that the immersion of the substrate in the electrolyte prior to the measurements causes this behaviour. SEM, EDX, XPS (X-ray photoelectron spectroscopy), SAM (scanning Auger microscopy) and IRRAS (infrared reflection absorption spectroscopy) measurements are used for surface characterisation and EBSD-measurements for determination of crystallographic orientation to reveal the influence on electrochemical growth. It is proven that zinc precipitates form on the temper rolled substrate during immersion and cause a nucleation process prior to electrodeposition and the subsequent change in electrocrystallisation as zinc is deposited on zinc instead of steel. The differences in the electrochemical measurements are well described by this theory. © 2014 Elsevier B.V.

Itani H.,Johannes Kepler University | Duchoslav J.,Johannes Kepler University | Arndt M.,Johannes Kepler University | Steck T.,CEST GmbH | And 5 more authors.
Analytical and Bioanalytical Chemistry | Year: 2012

Zn-Cr alloyed coatings electrochemically deposited are of high interest for leading steel manufacturing companies because of their novel properties and high corrosion resistance compared with conventional Zn coatings on steel. For tuning and optimizing the properties of the electrodeposited Zn-Cr coatings, a broad range of the deposition conditions must be studied. For this reason, two different types of material were investigated in this study, one with a low electrolyte temperature and one with an elevated electrolyte pH, compared with the standard values. Because different corrosion performance and delamination behaviour of the layers were observed for the two types, advanced surface analysis was conducted to understand the origin of this behaviour and to discover differences in the formation of the coatings. The topmost surface, the shallow subsurface region, and the whole bulk down to the coating-steel interface surface were analysed in detail by X-ray photoelectron spectroscopy (XPS) and high-resolution scanning Auger electron spectroscopy to determine the elemental and the chemical composition. For better understanding of the resulting layer structure, multiple reference samples and materials were measured and their Auger and XPS spectra were fitted to the experimental data. The results showed that one coating type is composed of metallic Zn and Cr, with oxide residing only on the surface and interface, whereas the other type contains significant amounts of Zn and Cr oxides throughout the whole coating thickness. © Springer-Verlag 2011.

Just Ch.,Ac2t Research Gmbh | Badisch E.,Ac2t Research Gmbh | Wosik J.,CEST GmbH
Journal of Materials Processing Technology | Year: 2010

Metal matrix composites (MMCs) are used to increase lifetime of parts of machines in environments where they undergo severe conditions, for instance abrasive wear or impact. When a metal matrix composite is manufactured, reactions between matrix and carbides take place and a reaction zone between matrix and carbides, the interface, is formed. It is shown in the literature, that the interface has an influence on the mechanical properties of MMC. Therefore, it is important to understand, how the interface develops, whose influences on the development exist and how the interface affects the mechanical properties of the MMC. Also the composition of the interface needs to be observed. The aim of this work is to give a qualitative description of the mechanical behaviour of carbide/matrix interface in relation with the interfacial reactivity at this interface. Furthermore, a selected MMC hardfacing alloy based on 60 wt.% WC/W2C and Ni matrix was manufactured by plasma transferred arc (PTA) process at variation of welding current to estimate the composition of the interface and mechanical properties of the whole composite material. A special designed single impact test (SIT) enabled investigation of impact wear behaviour at high single loads. The evaluation of interface properties was supported by optical microscopy, SEM, XRD investigations and hardness tests. In the literature damage mechanisms under impact are pointed out to decohesion and cracking of hard phases based on interface properties. In the SIT investigations of MMC hardfacing alloy based on 60 wt.% WC/W2C and Ni matrix it can be shown that welding current is controlling the formation of the carbide/matrix interface and furthermore the dominating wear mechanisms under high single loads in SIT. © 2009 Elsevier B.V. All rights reserved.

Ilo S.,ACT Research GmbH | Just C.,ACT Research GmbH | Badisch E.,ACT Research GmbH | Wosik J.,CEST GmbH | Danninger H.,Vienna University of Technology
Materials Science and Engineering A | Year: 2010

Hard-particle metal-matrix composites (MMC) are generally used to increase the lifetime of machinery equipment exposed to severe wear conditions. Depending on the manufacturing technology, dissolution reactions of hard phases undergo different temperature/time profiles during processing affecting the microstructure and mechanical properties of the MMCs. Therefore, quantification of the carbide dissolution effects on the microstructure and micro-mechanical properties is the key to success in the development and optimisation of MMCs. Dissolution kinetics of WC/W2C in Ni-based matrices were determined in the liquid-sintering with a well-defined temperature/time profile. Microscopic evaluation of the samples showed two intermediate layers between matrix and carbides. The layer thicknesses were quantitatively determined using image analysis. A kinetics relationship was used for modelling the interface layer growth as a function of processing time, temperature and Cr-addition. Furthermore, the micro-mechanical properties of the intermediate layers were examined using nanoindentation. Based on the chemical composition and the hardness of the intermediate layers, formation of mixed Ni- and W-carbides and/or borides on the interface microstructures was indicated. Results showed that the chemical composition and the micro-mechanical properties were almost constant within all the detected layers in the interface zone between matrix and carbides, indicating that the microstructure gradients were most dependent on the intensity of the MMC processing. © 2010 Elsevier B.V.

Lammel P.,Airbus | Lammel P.,CEST GmbH | Lammel P.,University of Paderborn | Kleber C.,CEST GmbH | And 2 more authors.
Galvanotechnik | Year: 2013

Airborne vehicles are exposed to a multiplicity of environmental effects, including those provoking substantial wear of components and their coatings. An overview is presented of erosive effects resulting from exposure to hard particles and water droplets as well as an analysis of the damage mechanism caused by these and their erosive effects. Laboratory-based erosion studies can simulate conditions found in actual flight and thus avoid the time-consuming and expensive trials which would otherwise be necessary. The principles of the various test methods used are set out. In order to protect structures and surfaces of aircraft from erosion, appropriate protective measures are necessary. These are primarily based on coatings as well as protective caps or films.

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