Oberflächenschutzschichten für metallische Hochtemperatur-Werkstoffe. Teil 1: Entwicklungstendenzen,Prüfung und Herstellung von Schutzschichten

Protection of High Temperature Metallic Materials against Oxidation . Part 1: Development Trends, Testing and Preparation of Protective Layers. A comparison is given of the chemical compositions of industrial Co- and Ni- high-temperature alloys used in the past years. Due to their relatively low Cr and Al contents the more recent super-alloys require additional oxidation protection. Theoretically, the refractory metals would allow much higher working temperatures than the super-alloys, but alloys based on such metals need a much more perfect oxidation protection. The fabrication testing and methods for such protective layers are briefly reviewed. The second part of this paper will describe some specific protective layers for super-alloys and refractory metals.     

Oberflächenfunktionalisierung von Kunststoffoptik

Surface Functionalization of Polymer Optics Transparent plastics have been used for optical applications with growing demand. This development is accompanied by a desire for extended surface functionalities like antireflection and hardening. Coating processes well established for glass optics cannot be applied in most cases. A manifold of polymer materials with different chemical surface states require special coating deposition parameters. In the first part of the tutorial the main plastic materials are introduced and their properties which are important for the vacuum deposition processes will be discussed.     

Oberflächenfunktionalisierung von Kunststoffoptik

Antireflection and other functional coatings Transparent plastics have been used for optical applications with growing demand. This development is accompanied by a desire for extended surface functionalities like antireflection and hardening. Coating processes well established for glass optics cannot be applied in most cases. Polymers properties which have to be taken into account for vacuum coating have been discussed in the first part of this tutorial. The second part is focused on the optimized coatings for plastic optics, especially for providing antireflective properties.     

Untersuchung der Verteilung und Intensität filamentierter Barrierenplasmen für die Behandlung von Oberflächen

The application of barrier discharges at atmospheric pressure in air expands on the market of plasma technology, because it is an ecological and cost‐effective alternative to other processes of surface treatment. These plasmas usually consist of a multitude of spatially and temporally localized filaments, whose distribution should be as even as possible for homogeneous treatment. This holds especially for the plasma treatment of sensitive goods such as wool or other textiles. In equipment for continuous pass of material the barrier arrangements often consist of a system cylinder – cylinder or cylinder – plane, whereby the gap width changes locally. Space distribution and intensity of filaments has been investigated by means of short‐time photography and spatially resolved measurement of current distribution and energy distribution derived from it. The local dependency found can be explained by means of a capacitive equivalent circuit.     

Oberflächenschutzschichten für metallische Hochtemperatur-Werkstoffe. Teil 2: Schutzschichten auf Superlegierungen und hochschmelzenden Metallen

Protection of High Temperature Metallic Materials against Oxidation , part 2; Protective Layers on Superalloys and High Temperature Materials. The structures of typical protective coatings of superalloys and Nb-alloys are briefly described and possible reasons for their failure are given. The importance of self-healing properties and of the reliability of such protective layers in any technical application is stressed. An order of magnitude of the duration of protection for different alloys is indicated for several coating types.     

Oberflächenbehandlung von Kohlenstoffasern und mechanische Eigenschaften von Laminaten

Surface Treatment of Carbon Fibres and Resulting Composite Properties In composites carbon fibres are used as reinforcing fibres with thermosetting and thermoplastic resins as martices. These carbon fibres differ strong in their micro-structure and therefrom in fibre properties. To achieve sufficiant composite properties special carbon fibre surface treatment methods are necessary. This paper describes a systematic study on oxidative surface treatment of carbon fibres by wet-, dry- and anodic oxidation. Further investigations by matrix variation show us the influence of matrix strength on the mechanical composite properties. Finally it is shown that in case of impact load composite fracture behaviour is controlled only by the fibre itself.     

Optische Oberflächencharakterisierung von plasmagespritzten stochastischen Strukturen

In this paper microstructures have been produced with a stochastic distribution by a thermal spraying process with different process parameters. An optical roughness measurement device has been used to measure these microstructures. Afterwards the measurement data is processed in order to identify each microstructure. Using this data several characteristics like the area, the volume and the depth of the microstructures as well as several porosities have been computed. These characteristics could be correlated to the process parameters. Furthermore, tribological experiments have been conducted with these surfaces and additional correlations between the friction value and the characteristics area, depth and the average roughness besides the structures have been performed.     

Messung von Rayleighwellen zur Untersuchung der Erosion an der Oberfläche kristalliner Werkstoffe mit Hilfe der Doppelpuls-Holographie

Measuring Rayleigh Waves to Investigate the Erosion at the Surface of Crystalline Materials by Means Double-Pulse Holographic Interferometry The repeated impact of solid particles on a material surface results in erosion. For technical applications as the pneumatic transport the particle diameters are varying between 10^?610^?3 m, the mean particle velocities are up to 30 m/s. In order to investigate experimentally the mechanism of erosion for crystalline materials, planar plates of austenitic steel are damaged due to the repeated impact of spherical particles. The elastic and plastic deformations, which are produced by this impact, result in propagation of longitudinal and transverse elastic waves into the material and of Rayleigh waves along the material surface. The amplitude of the surface deflection due to a single impacting particle is only 10^?810^?7 m. At different states of damage the surface deflection which is caused by such an impact is measured by means of double-pulse holographic interferometry. Because of the small amplitude of the Rayleigh waves two-reference-beam holographic interferometry is required. The initial wear of the material is recognized by the disturbed propagation of the surface wave.     

Oberflächen‐ und Randschichtcharakterisierung von hochgeschwindigkeitsgefrästem Stahl

Surface and subsurface characterization of high speed milled steel Surfaces und subsurface regions of workpieces generated by high speed milling were studied to support the understanding of micro‐processes of deformation and cutting. Microstructure, crystal structure, residual stress, and topography of the workpiece, and microstructure and shape of the chips were characterized. With low carbon and low alloyed steel the materials state is significantly influenced by the cutting parameters. The surface topography is related to the microtopography of the cutting edge of the tool. A deformation of the microstructure happens down to 15 μm under the surface. Residual stress has been measured within a 60 μm thick surface layer. The curvature of the ships increases with the cutting speed.     

Oberflächenaktivierung von Kunststoff mittels Plasma zur Haftvermittlung

Plasma activation of polymer surfaces for the adhesive bonding — a survey of praxis Several techniques are used for the permanent joining of components. In applications where welding or soldering cannot be applied due to the great heat development, the use of plasmas can prepare even otherwise chemically inert surfaces for the bonding process. This article presents the basic chemical concepts of this technique as well as its practical realization using the example of adhesion of polymers among themselves and to metals.     

Oberflächenmodifizierung von Titan zur Verbesserung der Grenzflächenverträglichkeit

Surface Modification of Titanium for Improvement of the Interfacial Biocompatibility We report the CVD‐polymerisation of amino‐functionalized [2,2]‐paracyclophane for polymer coating and functionalization of titanium surfaces. Additionally, the functionalization was carried out by silanization with 3‐aminopropyl‐triethoxysilane. The generated amino‐groups were used for covalent immobilization of bioactive substances to stimulate the adhesion and growth of osteoblasts. As bioactive substances the pentapeptide GRGDS and the growth factor BMP‐2 were chosen. The covalent bonding was achieved by activation with hexamethylene diisocyanate. Each modification step was characterized by X‐ray‐photoelectron‐spectroscopy (XPS), atomic force microscopy (AFM) and contact angle measurements. The covalent bonding of the bioactive substances was proven by radiolabelling and surface‐MALDI‐ToF‐MS. In vitro‐biocompatibility tests with primary, human osteoblasts demonstrated the improved cell adhesion and spreading on the bioactive modified titanium surfaces.     

Die thermische Stabilität von Eigenspannungen in kugelgestrahlten Oberflächen

Thermal Stability of Residual Stresses in Shot Peened Surfaces . In industry shop peening represents a well-known process to improve the fatigue properties of metallic components. However, the beneficial effect of the induced compressive residual stresses can be reduced if a component is subjected to higher temperatures during service. In this work the relief of the residual stresses as a function of time and temperature is calculated for a 12 %-chromium steel. Specifically, the results can be used for the prediction of the stress relief behaviour of gas turbine compressor blades. This model can also be applied to the determination of the mechanisms which are responsible for the residual stress relief. At temperatures above approximately 300 °C in this material the dominating mechanism is diffusion controlled creep whereas at lower temperatures the stress relief is caused by logarithmic creep.     

Oberflächenbeeinflussung von Modellschlagleisten durch Stoßkontakte mit Betonpartikeln

The influencing of the surface of an impeller bar pattern by impact contacting with concrete particles The wear appearing as a result of an impact strain by abrasion particels in an impact- crusher was simulate with a special test machine. With the impact wear test machine were investigated the effects of impacts at different groups of materials to investigate the wear behaviour versus the number of contacts. In view of the abrasive behaviour of the materials the tests demonstrate the necessitiy to consider the penetrating ability of the abrasive particels in the surface of the sample. By means of microphotos was developed a structural model for the abrasion of ductile areas of the material.