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Frontiers of Mechanical Engineering

Front. Mech. Eng.    2020, Vol. 15 Issue (3) : 496-503
Influence of direct electric current on wetting behavior during brazing
Kirsten BOBZIN1, Wolfgang WIETHEGER1, Julian HEBING1, Lidong ZHAO1, Alexander SCHMIDT1(), Riza ISKANDAR2, Joachim MAYER2
1. Surface Engineering Institute (IOT), RWTH Aachen University, 52072 Aachen, Germany
2. Central Facility for Electron Microscopy, RWTH Aachen University, 52074 Aachen, Germany
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The wetting behavior of liquid metals is of great importance for many processes. For brazing, however, a targeted modification beyond the adjustment of conventional process parameters or the actual set-up was not possible in the past. Therefore, the effect of direct electric current along the surface of a steel substrate on the wetting behavior and the formation of the spreading pattern of an industrial nickel-based filler metal was investigated at a temperature above T = 1000 °C in a vacuum brazing furnace. By applying direct current up to I = 60 A the wetted surface area could be increased and the spreading of the molten filler metal could be controlled in dependence of the polarity of the electric current. The electric component of the Lorentz force is supposed to be feasible reasons for the observed dependence of the electrical polarity on the filler metal spreading direction. To evaluate the influence of the electric current on the phase formation subsequent selective electron microscope analyses of the spreading pattern were carried out.

Keywords brazing      electric current assisted wetting      Lorentz force     
Corresponding Author(s): Alexander SCHMIDT   
Just Accepted Date: 16 April 2020   Online First Date: 14 May 2020    Issue Date: 03 September 2020
 Cite this article:   
Kirsten BOBZIN,Wolfgang WIETHEGER,Julian HEBING, et al. Influence of direct electric current on wetting behavior during brazing[J]. Front. Mech. Eng., 2020, 15(3): 496-503.
Fig.1  Top view cross section schematic sketch of the experimental setup indicating the used position of the samples. R: Electric resistance.
Chemical composition Weight percent/wt.%
Ni balance
Cr 7.0
Si 4.5
B 3.1
Fe 3.0
Tab.1  Chemical composition of B-Ni2 filler metal
Sample Position Electric current (DC)/A Temperature/°C Time/min
V1 Position 1 0 1080 10
V2 Position 1 60 1080 10
V3 Position 2 60 1080 10
V4 Position 2 ?60 1080 10
Tab.2  Wetting process parameter
Fig.2  Time vs. temperature, pressure, and electric current regime.
Fig.3  Macroscopic and light microscopic top view image of the wetting pattern of (a) V1: Position 1, I = 0 A and (b) V2: Position 1, I = 60 A (DC).
Fig.4  Applied system with (a) solid filler metal and (b) liquid filler metal.
Fig.5  Selective electron microscope cross section images of (a) V1: Position 1, I = 0 A and (b) V2: Position 1, I = 60 A (DC).
Fig.6  SEM cross section images and EDX-mappings at filler metal initial position of (a) V1: Position 1, I = 0 A and (b) V2: Position 1, I = 60 A (DC).
Fig.7  Macroscopic and light microscopic top view image of the wetting pattern of (a) V3: Position 2, I = 60 A (DC) and (b) V4: Position 2, I = ?60 A (DC).
Fig.8  Schematic sketch of electromagnetic fields in the furnace indicating the displacement of the electric field lines within the base material at position 2.
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