Diffusionslöten von Aluminium mittels PVD applizierter Lotzusatzwerkstoffe

Diffusion brazing of aluminium by PVD applied filler metals Diffusion brazing of aluminium and aluminium alloys precoated with filler metal components enables fluxless wetting and obtains braze joints of high strength at moderate brazing temperatures. Previously deposited components of filler metals on the base materials as thin film, using Arc‐PVD‐process lead during a subsequently diffusion brazing process to the formation of a local liquid phase (transient liquid phase). The liquid phase is formed from the deposited thin film material and the base material and is solidified isotherm due to diffusion procedures. In doing so braze joints of higher melting point than brazing temperature can be realised. In this work, vacuum brazing of the two systems, Al‐Cu and Al‐Cu‐Si have been investigated. Cu and Al‐Cu‐Si were deposited on the base material using Arc‐PVD‐process. The base materials were pure aluminum and EN‐AW6060. Metallographic and scanning electron microscope analyses proved that the braze seam area after the completed diffusion brazing process shows similar structure and composition as the base material.     

Aktivlöten von keramischen Segmenten für den Einsatz in verschleißkritischen Bereichen von Schmiedegesenken

Active brazing of ceramic inlays for the application in wear critical areas of forging dies The use of reinforcing ceramic segments in forging tools is investigated and has been successfully tested with model of dies recently. With reinforcing ceramic segments, however, the thermal widening of the steel tool is a major problem for forging dies. Further, only rotationally symmetrical ceramic inserts can be used as reinforcements which restricts the shape capabilities in tool design significantly. A considerably greater design flexibility is possible if the ceramic segments are brazed into the die body material. To this end, reactively brazed ceramic‐metal composites are to be developed and tested for feasibility in the forging process.     

Mikrostrukturieren von thermisch gespritzten Mo‐Schichten für Anwendungen im Bereich hoher Reib‐ und Verschleißbeanspruchungen

The properties of thermally sprayed coatings are dependent on many parameters such as the spraying material, substrate properties, and the injection parameters. In this study, the influence of two variable spray parameters (spraying distance and current) were investigated on molybdenum‐containing thermal spray coatings. Particularly, materials and surface characterizing properties were analyzed, and the dependence on each other was examined. The important surface parameters studied in this case are the porosity and the pore depth of the coatings. Following the correlation between spray parameters and coating properties, the influence of surface properties on the tribological behavior will be discussed, in comparison to an uncoated steel surface.     

Herstellung von hochporösen,endkonturnahen Titan‐Formkörpern für biomedizinische Anwendungen

Near‐net‐shape manufacturing of highly porous titanium parts for biomedical applications The production of highly porous titanium parts is attractive for biomedical applications. Preferrentially, these parts are produced by powdermetallurgical means using suitable spacer materials. Porosities up to 75 % and well defined pore sizes in the range of 0.1 to 2.0 mm are achieved adjusting the amount and the particle size of the spacer material. Up to now, near‐net‐shape manufacturing of highly porous parts was hindered by the plastic deformation of the sintered network during machining leading to a partial or complete closing of the open porosity. A new manufacturing route is presented, where the shaping is already done in the unsintered state starting from pressed compacts. The stability of the compacts was found to be sufficient to machine the compacts without additional binders. The manufacturing route was successfully applied to the prototype of an acetabular cup. Additionally, some investigations are presented characterizing the highly porous titanium.     

Löten von Diamant – Grenzflächenreaktionen. und Benetzung

Diamond Brazing – Interfacial Reactions and Wetting Diamond tools are increasingly gaining importance as cutting materials for various construction materials. The quality of synthetic diamonds, monocrystalline as well as polycrystalline or CVD‐diamonds has been significantly improved over the last years. Integrating these cutting materials requires adequate joining technologies that produce sound joints without exposing the temperature sensitive diamond to too elevated temperatures. The paper highlights current developments in the joining of synthetic diamonds to steel and cemented carbide. Owing to their covalent atomic bonding diamonds cannot easily be wetted and joined by employing conventional brazing alloys. Hence, active agents are needed to foster an interfacial reaction. Different active filler concepts are presented and discussed regarding their joint formation. The brazing temperatures influence not only possible diamond degradation but also the interfacial decomposition of the diamond due to the formation of corresponding reaction layers.Active brazing, monocrystalline     

Entwicklung eines stoffschlüssigen Fügeverfahrens für Glaskohlenstoff und einem C/C–SiCN‐Verbundwerkstoff für ein innovatives Hochtemperatur‐Messsystem

Conventional high temperature (>1400 °C) measuring techniques are very limited. Thermal protective covering of temperature measuring elements in molten metals usually are single‐use systems. As a part of a research and development project a new temperature measuring system is being developed. The requirements for this protective cover are extremely complex. Not only does it has to be resistant to high temperatures, media in molten metals, fractures and thermal shocks, it also has to be gastight and thermal conductive. The compounds used currently for these covers don't fit this profile. Laminated C/(C/C–SiCN) hybrid composites are a new approach, consisting of glassy carbon and a C/C–SiCN composite. In order to ensure the media resistance of the protective cover a fitting lamination is applied by means of a thermal spraying. Due to the extreme requirements of the joining points the joining of this lens barrel hybrid composite with the gastight seal is quite difficult. The joints have to maintain an adequate mechanical stability and gasthightness for up to 700 °C. Other reliable joining techniques for graphite are supposed to be applied to glassy carbon. Regarding this active hard soldering was investigated. In this article conventional active hard soldering agents with varying titanium contents and under variation of other parameters are tested for their suitability as a soldering agent. The soldered samples were material graphically, micromechanically and fractographically characterised.     

Innovative Lösungsansätze für das Fügen von AMCs

Innovative solutions for joining AMCs The application of aluminium matrix composite materials (AMC) in structural components requires appropriate joining technologies. One important aspect is the preservation of the properties of the composite during the joining process. The thermal load of the base material is particularly critical as a result of the process‐related heat input. In order to keep it low, adapted joining technologies and low‐melting fillers are essential. The combination of an ultrasound process and an induction heating offers various advantages. On the one hand, the ultrasound introduction achieves a destruction of the surface oxides and therefore a wetting of the joining surfaces without the use of flux. On the other hand, local inductive heating allows to realise very short joining times so that the heat input into the base materials to be joined can be reduced to a minimum. The application form of the fillers plays an important role for the achievable compound strengths. Selected test results will show the advantages and disadvantages of different variants.