Electron beam brazing of AISI 304 and copper dissimilar materials

The aim of the paper is focusing on the brazeability of stainless steel AISI 304 and copper Cu-ETP (electrolytically tough pitch) dissimilar materials by electron beam. The thickness of base materials was 1 mm. Cusil eutectic brazing alloy (72Ag-28Cu, AWSBAg-8) in the form of thin foil was used as filler material. Overlapped joints were manufactured using defocused vertical electron beam. The effect of beam current on braze appearance, microstructure, and microhardness of brazed joints was investigated. The scanning electron microscopy indicated the possibility of obtaining defect-free joints. The results show that the binary Ag-Fe equilibrium diagram is expectedly the microstructure even at the moderate cooling and solidification rates expected under the used electron beam brazing conditions and parameters. Beam current is the main brazing parameter influencing the joint quality. Optimum brazing parameters were as follows: beam current 6 mA, brazing speed of 5 mm/s, and 50 passes at constant accelerating voltage (U = 55 kV), focusing current (I f = 990 mA) across the upper material length—Cu.