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

• We deposit Fe–Cr–B-based alloy onto plain carbon steel using the CSC-MIG process.
• We model the solidification behavior using thermodynamic calculation.
• As deposited alloy consists of (Cr,Fe)2B plates embedded in Fe-based matrix.
• We study the effect of the welding heat input on the microstructure.

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.