Understanding the solidification and microstructure evolution during CSC-MIG welding of Fe-Cr-B-based alloy

The present is a study of the solidification and microstructure of Fe-28.2%Cr-3.8%B-1.5%Si-1.5%Mn (wt.%) alloy deposited onto a 1020 plain carbon steel substrate using the controlled short-circuit metal inert gas welding process. The as-solidified alloy was a metal matrix composite with a hypereutectic microstructure. Thermodynamic calculation based on the Scheil-Gulliver model showed that a primary (Cr,Fe)₂B phase formed first during solidification, followed by an eutectic formation of the (Cr,Fe)₂B phase and a body-centered cubic Fe-based solid solution matrix, which contained Cr, Mn and Si. Microstructure analysis confirmed the formation of these phases and showed that the shape of the (Cr,Fe)₂B phase was irregular plate. As the welding heat input increased, the weld dilution increased and thus the volume fraction of the (Cr,Fe)₂B plates decreased while other microstructural characteristics were similar.