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Während der An-und Abfahrvorgänge mehrstufiger Hochdruckpumpen durchlaufen mediumgeschmierte Axial-und The product-lubricated axial and radial bearings installed in multistage high-pressure pumps inevitably encounter severe mixed friction conditions as the pumps start and stop. This leads to extremely high tribological loads on the bearing components, compounded by the effects of a highly corrosive pumped fluid. The present paper describes a laser cladding process which produces nearnet-shape coatings of new, highly corrosion and wear resistant functional layers which can be deposited directly on high-alloy stainless steels without requiring additional buffer layers and without affecting the mechanical properties and corrosion resistance of the substrate. The results cover the solidification behaviour of the coatings as well as the microstructure resulting from various heat treatment conditions. In addition, the technological properties of the coatings and the resulting composites are discussed. The coating systems are tested as to their corrosion resistance and tribological characterization in a pump-specific tribological system.

The paper describes a new approach to characterize metallic materials by a novel instrumented notch impact test for samples with small specimen size. A piezo‐electric sensor mounted on the pendulum hammer provides force information during the fracture process. By numerical integration of the signal the absorbed impact energy can be calculated very exactly. Further information about the fracture behavior can be extracted from the resulting force‐displacement‐diagram. Several duplex stainless steels in different heat treatment conditions were tested and compared to standard Charpy impact testing specimen. It is concluded that different grades of embrittlement of duplex materials can be detected with high accuracy. Due to a data acquisition rate of 250 kilo‐samples/second and limited stiffness of the pendulum hammer impact energies of less than 7% of maximum energy materials with high brittleness can only be characterized qualitatively.

Seawater desalination based on the reverse osmosis process requires a variety of hydraulic systems. The material concepts of these hydraulic systems are designed to reliably resist the corrosive properties of seawater and brine as well as the tribological loads. Strong tribological loads typically occur during the start-up and shutdown of multi-stage high-pressure pumps. Thermally sprayed coatings can be used to increase the wear resistance and also the tribological properties of bearings. Also in pressure exchangers for energy recovery, high tribological loads occur on the surfaces of rotors which operate with a clearance gap of 40-100 mm. Today, thermally sprayed coatings are used for the surface protection of these rotors. To resist the various tribological loads, the material pairs are optimized for each case. Thermally sprayed coatings with high surface hardness have proven to be particularly successful. A coating system, based on a CoCr matrix, has been developed especially for these applications.

Frau Professor Dr. E. Wendler-Kalsch u r n 60. Geburtstag gewidmetDuplex-Stahle werden aufgmnd ihrer guten Korrosionseigenschaften in vielen Bereichen der Chemischen Industrie sowie der Kraftwerks-, Meeres-und Umwelttechnik eingesetzt. Fur gleichzeitig korrosiv und verschleiRend wirkende Medien stehen ausscheidungsgehartete Varianten und solche rnit gering erhohten Kohlenstoffgehalten zur Verfugung. Die dadurch erzielte Verbesserung der Verschleifieigenschaften bedingt jedoch eine Verminderung der Korrosionsbestandigkeit und damit auch eine Einschrankung des Anwendungsbereiches. Ebenso erreichen derartige Stahle bei weitem nicht die VerschleiRbestiindigkeit carbidischer HartguRsorten, die jedoch nur in annahernd pH-neutralen Wassern verwendet werden konnen. Bei der Fordemng chemisch aggressiver Medien mit hohen Feststoffanteilen muRten deshalb bisher entweder verkurzte Standzeiten der Komponenten akzeptiert oder teure Sonderwerkstoffe verwendet werden. Die Verbesserung der Kombination aus tribologischen und elektrochemischen Eigenschaften von Duplex-Stahlen ist daher das Ziel vielfaltiger Entwicklungsarbeiten. Je nach chemischer Zusammensetzung und der Art der Hartphasen ergeben sich daraus unterschiedliche Korrosions-und Verschleifieigenschaften, die am Beispiel einer Versuchsschmelze und einer neuentwickelten Legierung beschrieben werden.Due to their good corrosion properties, duplex stainless steels are used in many fields of chemical industry as well as power stations, marine and environmental engineering. Precipitation-hardened variants and alloys with slightly increased carbon content are available for handling media causing simultaneous corrosion and wear. This improvement in wear properties, on the other hand, reduces their corrosion resistance and thus limits their actual fields of applications. Also, the wear resistance achieved by these steels is far inferior to that of white iron, which, however, can only be used in water with close-to-neutral pH-value. So far, handling chemically aggressive media either entailed short service lives or required expensive special materials. Many development activities are therefore aimed at improving the combination of tribological and electrochemical properties of duplex stainless steels. Different chemical compositions and types of hard phases result in varying corrosion and wear properties which are described on the basis of a test melt and a new-developed alloy.