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| Abstract No.: |
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Scheduled at:
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Tuesday, June 21, 2022, Saal Brüssel 4:20 PM
Properties of brazed joints
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| Title: |
Alloying-dependent microstructure influence on corrosion fatigue mechanisms of vacuum brazed AISI 304L/NiCrSiB joints
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| Authors: |
Johannes Otto* / Dortmund University of Technology, Germany
Frank Walther / Dortmund University of Technology, Germany
Anke Kalenborn/ Dortmund University of Technology, Germany
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| Abstract: |
For the reliable and economical use of vacuum-brazed components under corrosive influences, the understanding of the alloy-process-structure-property relationship is elementary. In this study, three different nickel-based alloys in form of rapidly quenched foils with alternating chromium and molybdenum content are produced and used for brazing cylindrical butt joints at two different holding times at 1160°C, resulting in six different microstructural formations. Different phases such as borides and silicides are determined, which differ in terms of size, quantity and location. Corrosion fatigue tests are carried out using a servo-hydraulic fatigue testing system with a corrosion chamber that was constantly flowed through by a moderate synthetic exhaust gas condensate. In addition to tactile strain measurements, the electrochemical open-circuit potential is recorded to obtain information about passive layer development and crack opening. Furthermore, pure corrosion and tensile tests are carried out to separate corrosive and mechanical effects. Among other findings, it is shown that a high chromium content provides a great corrosive resistance but reduces the fatigue lifetime due to the formation of complex chromium-borides and nickel-silicides, especially due to short holding time. Finally, fractographic investigations enabled an understanding of the fracture mechanisms.
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