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Brazes for extremely high temperatures

 
: Martin, Hans-Peter; Roszeitis, Sven; Matthey, Björn; Herrmann, Marion; Graffé, Marius; Lippmann, Wolfgang; Schmidt, Marcus Peter; Burkhardt, Ulrich; Michaelis, Alexander

Deutscher Verband für Schweißtechnik e.V. -DVS-, Düsseldorf:
Brazing, high temperature brazing and diffusion bonding : LÖT 2019, Lectures and posters of the 12th International Conference, Aachen, 21th to 23th May 2019
Düsseldorf: DVS Media, 2019 (DVS-Berichte 353)
ISBN: 978-3-96144-060-3
ISBN: 3-96144-060-3
pp.199-206
International Conference on Brazing, High Temperature Brazing and Diffusion Bonding (LÖT) <12, 2019, Aachen>
English
Conference Paper
Fraunhofer IKTS ()
ceramic; brazing; high temperature; refractory metal alloy; thermal analysis; phase

Abstract
Ceramic materials are widely used for extreme temperature conditions. The sucessful integration of ceramics into devices strongly depends on appropriate joining procedures. The limits of joint material combinations are mostly defined by the joint between. Therefore high temperature brazes are required for high temperature applications. Refractory metals may be one option in joining ceramics as they have been already used for diffusion joining as molybdenum foils to combine ceramic materials. The knowledge about refractory metal alloys as high temperature braze is very limited. We started to analyse the data about phase diagrams of promissing metall alloys in the systems Ni-Ta, Ti-Al, Zr-Ti, Zr-W, Zr-Ni and Zr-Ta. The chemical systems and interactions with ceramics were thermodynamically analysed by use of FactSage program. Information about the melting behaviour and the chemical interactions with ceramics were gained from thermoanalytical experiments up to 2000 °C. The formation of the crystalline phases was analysed by FESEM/EDX/EBDS and XRD measurements. Promissing alloys were used to manufacture samples of joined SiC-SiC or Al2O3-Al2O3 ceramics. Additionally combinations of tungsten with SiC were tested in joining with the potential refractory braze alloys. The achieved quality of the joined materials was estimated by mechnical strength experiments and helium leak testing of samples. The potential of high temperature braze alloys shows that refractory products can be produced by using specific brazing processes. This allows to access new functionalities of ceramic-ceramic and ceramic-metal components.

: http://publica.fraunhofer.de/documents/N-555184.html