Microstructure of Butt Joint of High-Silicon Steel Made Using CO2 Laser Welding and Inconel 82 Filler

A nickel-based filler wire, Inconel 82, was applied to weld a high-silicon steel plate with a chemical composition in wt% of 2.6 Si, 0.5 Al and Fe balance. The chemical composition of the heterogeneous weld bead was deviated from that of the conventional alloy due to incomplete mixing/convection between the filler wire and base metal in the weld pool. The microstructure of the weld bead was examined in greater depth by FESEM/EBSD, EPMA/WDS and STEM/EDS in the experiment. The heterogeneous weld bead was primarily composed of austenite and martensite, and mainly governed by the Ni concentration. A Schaeffler diagram based on the ratio of Cr and Ni equivalents in the selected positions of the weld bead was used to predict the structure and phase(s) of the Fe-based weld bead. A methodology for the analysis of a weld metal with an unconventional alloy composition has been proposed in the study.