Parametric study of surface melting in zinc-aluminium coated steels

The corrosion resistance of Al-Zn-Si coated steel sheets is superior to traditional galvanised products because they combine the barrier protection of aluminium with the sacrificial protection of zinc. The corrosion resistance can be further improved by using laser surface re-melting and rapid solidification to refine the coating microstructure. To achieve the desired microstructural changes by surface melting, the surface temperature and treated-depth of the components must be precisely controlled and this depends on the laser parameters such as power, spot size and processing speed. This paper presents the results of a parametric study of laser surface melting of zinc-aluminium coatings. A model was used to determine the processing conditions required to achieve an optimal surface microstructure. The model results were consistent with the observed microstructure of both the coating and the steel substrate. This analysis provides a better understanding of the effect of the processing parameters on the coating microstructures.