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Additive manufacturing technologies enable lightweight, functionally integrated designs and development of biomimetic structures. They contribute to the reduction in material waste and decrease in overall process duration. A major challenge for the qualification for aerospace applications is the surface quality. Considering Ti-64 laser powder bed fusion (LPBF) parts, particle agglomerations and resulting re-entrant features are characteristic of the upper surface layer. Wet-chemical post-processing of the components ensures reproducible surface quality for improved fatigue behaviour and application of functional coatings. The 3D SurFin® and chemical milling treatments result in smoother surface finishes with characteristic properties. In order to characterise these surfaces, three methods for surface texture measurement (contact and non-contact) were applied, namely confocal microscopy, fringe projection and stylus profilometry. The aim of this work was to show their suitability for measurement of laser powder bed fusion as-built and post-processed surfaces and compare results across the evaluated surface conditions. A user-oriented rating of the methods, summarising advantages and disadvantages of the used instruments specifically and the methods in general, is provided. Confocal microscopy reaches the highest resolution amongst the methods, but measurements take a long time. The raw data exhibit large measurement artefacts for as-built and chemically milled conditions, requiring proper data post-processing. The stylus method can only capture 2D profiles and the measurement was restricted by particle agglomerations and craters. However, the method (process and instrument) is entirely standardised and handheld devices are inexpensive, making it accessible for a large group of users. The fringe projection method was the quickest and easiest regarding measurement and data post-processing. Due to large areal coverage, reproduction of location when performing repeat measurements is possible. The spatial resolution is lower than for confocal microscopy but is still considered sufficiently high to characterise the investigated surface conditions.

This paper evaluates the applicability of two wet-chemical treatments for structural bonding of titanium alloy Ti6Al4V. The anodising processes, NaTESi and N4-Process, are based on electrolytes containing sodium hydroxide and complexing agents, but while NaTESi process contains ethylenediaminetetraacetic acid, a particularly hazardous chemical, N4-Process is a REACh compliant electrolyte. Scanning electron microscopy and transmission electron microscopy were employed to evaluate the oxide layer formed after the anodising processes. The long-term durability and the resultant adhesion properties on titanium were assessed by means of floating-roller-peel test. Both investigated anodising processes lead to oxide layers revealing a highly porous nanostructure (thickness between 150–600 nm) according to scanning electron microscopy and transmission electron microscopy analyses. The mechanical tests lead to negligible differences between processes, performing higher peel resistance when compared to only alkaline etched samples, especially after 1000 hours ageing at 50 °C and 95 % relative humidity. The results indicate that N4-Process is a promising treatment to enhance the long-term durability of bonded titanium joints, especially under hot and wet conditions. In diesem Artikel wird die Anwendbarkeit von nasschemischen Vorbehandlungen fur das strukturelle Kleben von Ti6Al4V Titanlegierungen untersucht. Die untersuchten Anodisierprozesse, NaTESi und N4, basieren auf Elektrolyten mit Natriumhydroxid und Komplexbildner. Wahrend beim NaTESi-Prozess Ethylendiamintetraessigsaure als Komplexbildner eingesetzt wird, kommt beim N4-Prozess ein REACh-konformer Komplexbildner zum Einsatz. Die resultierenden Oberflachen werden mittels Rasterelektronen- und Transmissionselektronenmikroskopie charakterisiert. Neben der Oberflachentopografie werden auch die Haftungseigenschaften der resultierenden Oberflache gepruft. Hierzu wird der Rollenschaltest sowohl im trockenen Zustand als auch nach der Auslagerung im feucht-warmen Klima durchgefuhrt. Die Charakterisierung der Oberflachentopographie zeigt, dass beide Prozesse zu einer nanostrukturierten und kristallinen Oxidschicht mit einer Dicke zwischen 150 nm und 600 nm fuhren. Die Ergebnisse der Rollenschaltests verdeutlichen, dass beide Prozesse zu vergleichbaren Schalfestigkeiten fuhren. Im Vergleich zu einer nur alkalisch gebeizten Probe, konnten jedoch deutlich hohere Festigkeiten erzielt werden. Vor allem nach der Alterung der Proben fur 1000 h bei 50 °C und 95 % rH, lassen sich deutliche Unterschiede erkennen. Wahrend die nur gebeizten Proben einen deutlichen Abfall in der Schalfestigkeit zeigen, fuhren die Verfahren NaTESi und N4-Prozess zu einer guten Langzeitstabilitat.

In this study, the interaction between a self-organized TiO 2 -nanotube layer formed by an anodizing procedure and a post-treatment with different water repellent coatings is investigated. Therefore, a conceptional model of these interactions is experimentally explored. Ti6Al4V samples are anodized using a fluoride-containing electrolyte. Using an anodizing voltage of 30 V, a homogeneous layer of TiO 2 -nanotubes with a pore diameter of 68.1 ± 3.8 nm and oxide layer thickness of 589.2 ± 23.7 nm could be generated on the surface. The anodization increases the surface area in comparison to the original state. To achieve water repellent surface properties the TiO 2 -nanotubes are functionalized by a selection of coating systems. Two different coating systems (coating 1: fluoroalkylsilane based; coating 2: perfluoropolyether based) are investigated within this study. By means of physical and chemical analyses both morphology and composition of the TiO 2 -nanotube surface are characterized. The scanning electron microscope (SEM) analyses illustrate that the tube morphology is not covered by the different coating systems. The chemical composition of the two different coatings is investigated by X-ray photoelectron spectroscopy (XPS). The results indicate that only the boundaries of the TiO 2 -nanotubes are covered by the coatings. However, the XPS results reveal that the different coatings do not fully infiltrate the tubular structures. Only the first nanometers (15–20 nm) are covered. To characterize and evaluate the superhydrophobic properties of the modified surfaces, the dynamic contact angles are measured. Each individual coating system shows a contact angle in excess of 150°. Surfaces that are simply degreased in an alkaline solution, without post-treatment with a water repellent coating show a contact angle of 21.9 ± 5.4°. Hence, it becomes evident that only the combination of a surface nanostructuring and a water repellent coating leads to superhydrophobic surface properties.

This paper evaluates the deposition of silica layers at atmospheric pressure as a pretreatment for the structural bonding of titanium (Ti6Al4V, Ti15V3Cr3Sn3Al) in comparison to an anodizing process (NaTESi process). The SiO2 film was deposited using the LARGE plasma source, a linearly extended DC arc plasma source and applying hexamethyldisiloxane (HMDSO) as a precursor. The morphology of the surface was analyzed by means of SEM, while the characterization of the chemical composition of deposited plasma layers was done by XPS and FTIR. The long-term durability of bonded samples was evaluated by means of a wedge test in hot/wet condition. The almost stoichiometric SiO2 film features a good long-term stability and a high bonding strength compared to the films produced with the wet-chemical NaTESi process.

In the aircraft industry, an increasing demand for adhesion promotion layers for titanium based materials is observed to replace polluting and unhealthy substances. Plasma enhanced chemical vapour deposition (PECVD) at atmospheric pressure (AP) seems to be favourable for the deposition of thin silica-like layers. In this work, a linearly extended and scalable DC arc plasma source is used for PECVD of silica layers on Ti 6 Al 4 V. The influence of the precursor chemistry is evaluated for HMDSO and TEOS precursors. Using HMDSO, hydrophobic almost stoichiometric SiO 2 coatings with a carbon content of 3 at.-% to 5 at.-% are deposited on the titanium alloy substrate. For TEOS, hydrophilic carbon-free stoichiometric SiO 2 coatings are deposited. The dynamic deposition rate for TEOS is 3 times lower than that for HMDSO (up to 640 nm•m/min). For the intended coating of slightly curved substrates, the film properties and deposition rates are studied for different working distances from 20 mm up to 60 mm. For 60 mm the deposition rate is reduced by a factor 6 compared to 20 mm, also the index of refraction of the film decreases from 1.45 at 20 mm distance to 1.39 at 60 mm. With increasing distance, the particle size and concentration on the surface increases and leads to less dense structures than in the case of shorter distances. The wedge test is used to evaluate the adhesion properties of the layer. The HMDSO-based coatings exhibit a good long-term durability and a high bonding strength comparable to that of the currently used standard pre-treatment, but without the use of harmful substances.

Leading edge contamination caused by insects is problematic for modern aircraft utilizing laminar flow aerofoils. The residue of crushed insect bodies adhering to aircraft leading edge surfaces can cause transition of the boundary layer, from laminar to turbulent, resulting in a significant increase in drag and therefore causing an increase in fuel consumption. Consequently, current research is focused on the evaluation of novel low surface energy coatings that will reduce or prevent insect adhesion. Insect residue adhesion tests were conducted on a range of surfaces, from superhydrophobic to hydrophilic. Surface free energy of the investigated substrates was obtained from measured dynamic contact angle values and surface roughness was measured using profilometry. Live insect testing with Drosophila melanogaster and Drosophila hydei was conducted using an insect delivery device inserted into a medium-speed wind tunnel. Tests were conducted at speeds ranging from 90 to 100 m/s (speeds representative of those on take-off and landing of a commercial passenger aircraft). Topography of insect residues was characterized using scanning electron microscopy and confocal laser scanning microscopy. Results obtained indicate that coatings with high surface roughness values and low wettability exhibit good anti-contamination properties.

Die Langzeitbestandigkeit von Metallklebverbindungen hangt masgeblich von den Wechselwirkungen zwischen den Polymeren und der meistens oxidbedeckten Oberflache ab. Um ein Versagen der Verbindung zuverlassig zu verhindern ist es wichtig, deren Veranderungen auch im Laufe des Produktionsprozesses zu kennen und zu bewerten.

The recent generation of aircraft is manly built out of CRFP (Carbon fiber reinforced plastic). To ensure galvanic compatibility Titanium alloys are used at connecting points to metallic structures. The increased use of Titanium alloys due to their good mechanical properties has highlighted the need for structural bonding as joining method to combine Titanium with CFRP. However, long-term stable adhesion on Titanium is still an issue. Currently mainly wet-chemical processes are applied to improve adhesion on Titanium alloys. Since wet-chemical treatments often comprise the use of hazardous chemicals dry environmentally friendly surface functionalization processes are pushed more into focus. PECVD (Plasma enhanced chemical vapour deposition) at AP (Atmospheric pressure) seems to be favorable for the deposition of silicon dioxide films as an adhesion promoter layer. In the present work, the deposition of silicon dioxide adhesion layer (from HMDSO (Hexamethyldisiloxane) as precursor) on titanium alloys is described for a linearly extended and scalable DC arc plasma source (LARGE). The wedge test is used to evaluate the adhesion properties of coated titanium samples in comparison to the standard used NaTESi anodizing process. The results show that the atmospheric pressure plasma process leads to good long-term durability and to high bonding strength which is comparable to the used standard pre-treatments.

This paper evaluates wet-chemical pre-treatments (alkaline etching, anodising) and a plasma treatment for structural bonding of titanium (Ti6Al4V). The main objective of this study is the comparison of the applicability of the plasma pre-treatment to wet-chemical treatments on titanium for structural bonding. In this context, an atmospheric pressure plasma device was used to deposit thin functional films from hexamethyldisiloxane (HMDSO) precursor on titanium. X-ray photoelectron spectroscopy (XPS) was employed to assess the chemical composition of the surface after different pre-treatments on the titanium substrate, while the morphology and the film thickness were investigated with scanning electron microscopy (SEM). The adhesion properties on titanium were evaluated by means of a wedge test in hot/wet conditions. After bonding tests the fracture surface and the failure loci were analysed. Using a long arc plasma generator and HMDSO precursor almost stoichiometric SiO2 coatings were obtained on the titanium substrate. These coatings exhibit good long-term durability and bond strength compared to an alkaline etching in the wedge test. The investigated anodising process leads to oxide layers revealing a highly porous nanostructure. In contrast to the alkaline etching, the plasma derived coatings and the oxide layer produced by the anodising process exhibit a higher micro, respectively nano roughness, and hence a better long-term durability.

The department “organization and information technology” (OIT) of the Faculty of Medicine of the “Ludwig-Maximilians-Universität München” introduced a system to centrally manage user accounts and security during the last two years. The initial state was that we had several user directories for different services, resulting in high operating expense. We describe the aims, the concepts, the techniques, the realization and the difficulties we had introducing a central user directory. The new central user directory covers not only authentication, but also authorization in the connected subsystems. The following subsystems are connected: Windows logon, Email and Calendaring, various intranet services like medical documentation system, diagnostic findings of clinical chemistry or radiology, remote access to Email and Calendaring via a firewall, RADIUS and last but not least logging on to SAP, which is our ERP (enterprise resource planning system).