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7851 |
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Tuesday, September 12, 2023, Mailand 9:30 AM Moderne Fügeverfahren - Löten |
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Experimentelle Validierung thermodynamischer Vorhersagen des Temperatur-Zeit-Zyklus für hochtemperaturgelötete Bauteile zur Optimierung ihrer Eigenschaften |
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Wolfgang H. Müller / Institut für Mechanik, Fachgebiet Kontinuuumsmechanik und Materialtheorie, TU Berlin, D Alexander Morozov* / TU Berlin, Institut für Mechanik, FG Kontinuumsmechanik und Materialtheorie, D Aleksei Sokolov/ TU Berlin, Institut für Mechanik, FG Kontinuumsmechanik und Materialtheorie, D Jonas Maiss/ Hochschule Niederrhein, D Johannes Wilden/ Hochschule Niederrhein, D Sebastian Glane/ TU Berlin, Institut für Mechanik, FG Kontinuumsmechanik und Materialtheorie, D |
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High-temperature nickel brazing is a common process with a wide range of applications, e.g., in the chemical industry, machine, plant and tool construction, and in aerospace applications. However, depending on the width of the brazing gap, undesirable brittle phase formation can occur during the process. The brittle phase can appear as a disperse phase or as a nearly continuous phase in the middle of the brazed seam. Depending on the extent of the brittle phase, this can lead to a deterioration in the mechanical properties of the brazed seam. An established method to avoid unwanted brittle phase formation is the use of brazing gap widths of maximum 50 µm. However, this requires high manufacturing precision, which results in increased time and cost. The occurrence of the brittle phase in the brazing gap is a result of alloying with chemical elements like boron, silicon and phosphorus, which serves to lower the melting point of nickel. By determining the diffusion coefficients of a multi-phase base and brazing materials and by solving the diffusion problem, the desired element concentration in the seam can be achieved. With this understanding, an optimal temperature-time cycle can be established to minimize the formation of brittle phase, particularly for gaps wider than 50 µm. This leads to an increase in the strength of the connection, which can almost reach the strength values of the base materials. Furthermore, it is possible to quantify the influence of the brittle phases on the connection strength and thereby to tolerate a certain residual brittle phase fraction in the brazed seam. This offers the potential to reduce the necessary process time and the associated costs without negatively affecting the mechanical properties. |