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826 |
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Tuesday, June 19, 2007, Brüssel 10:40 AM Grundlagen und industrielle Anwendungen des Lötens Fundamentals and industrial application of brazing |
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Shielding gas brazing of martensitic stainless steel with Cu-free Ag-based filler metals |
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Christian Leinenbach* / EMPA - Swiss Federal Laboratories for Materials testing and Research
Laboratory for Joining and Interface Technology, Schweiz Natalie Gelder / TU Kaiserslautern, Lehrstuhl für Werkstoffkunde, jetzt: BASF AG, Ludwigshafen, Deutschland Ulrich Klotz/ EMPA-Swiss Federal Laboratories for Materials Testing and Research, Schweiz |
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Shielding gas furnace brazing is widely applied in industry as a quick and cost-effective method for joining components used in the chemical industry and for power generation, e.g. compressor impellers or turbine parts which are subjected to complex loading conditions. The filler metals used should be easy to process and have adequate mechanical properties, even at temperatures up to 300 °C, as well as high corrosion and oxidation resistance. The use of Cu (as an alloying element) is ruled out in order to prevent possible chemi-cal reactions between process gases and the filler metal. These property requirements are fulfilled only by a small number of brazing alloys. In general, Au or Pd-based alloys are used for brazing the above mentioned components, but due to their steadily increasing price, a replacement of the precious metals by cheaper al-ternatives is desirable. In the present work, the potential of Cu-free Ag-based filler metals as possible candidates was explored for brazing the martensitic stainless steel X3CrNiMo13-4, which is used, for example, for turbo compressor wheels. Apart from the commercially available alloy Ag-5Pd, two experimental alloys in the Ag-Au-Ni-Pd sys-tem were investigated. The filler metals showed an excellent wetting behaviour and could be processed at temperatures be-tween 1020 and 1040 °C. This temperature range is suitable for integrating heat treatments of the X3CrNiMo13-4 steel in the brazing process without pronounced grain growth. Brazed specimens were char-acterized with respect to their microstructure as well as their mechanical and corrosion properties and com-pared to specimens brazed with the commonly used filler metal Au-18Ni. |