Influence of filler wires on hardness and coating dilution in high-speed laser-welded Al–Si-coated 22MnB5 steel

22MnB5 steel blanks (Usibor ® 1500) are widely used in automotive crash-resistant components because of their high strength. However, laser welding of Al–Si-coated 22MnB5 is challenging because coating dilution in the weld pool promotes soft δ-ferrite phase formation, reducing weld strength. An industrial solution is laser-ablation, while filler wire addition provides an alternative means to modify fusion-zone chemistry, with or without ablation. In this study, micro-structural development and mechanical performance of laser-welded Al-Si-coated 22MnB5 were investigated using ER4130 and ER420 filler wires. Energy-dispersive spectroscopy showed reduced bulk aluminum-(Al) content in welds with both filler wires relative to as-received welded hot-stamped welds, correlating with reduced δ-ferrite formation and increased martensite content. Higher chromium in ER420 further enhances hardenability, while carbon addition on wires further promoted martensite formation. These findings offer insights for Cr–C-based filler wire selection and advancing laser welding strategies for high-strength structural applications.