Wetting and solidification characteristics of aluminium on zinc coated steel in laser welding and brazing

Bead-on-plate laser brazing and overlap laser welding of zinc-coated steel and aluminium is investigated. It is shown that the characteristic tendencies from recent single droplet model experiments in terms of solidification and wetting length can be applied to the case of bead-on-plate brazing but are different in case of overlap welding. Based on a straightforward model for estimating evaporative heat loss, it is shown that heat dissipation in case of bead‐on‐plate brazing and single droplet wetting might be significantly affected by evaporating zinc. A proper breakage of oxide layers seems to be mandatory to initiate spreading on zinc coated surfaces. The occurrence or lack of this necessary effect could be a potential reason for the diverging wetting behaviour observed for overlap welding compared to bead‐on‐plate brazing or single‐droplet wetting.