Thermal modification of zinc-aluminum coated steel using lasers

Abstract

Zn-55%Al-1.6%Si coated steel products combine the barrier protection of aluminium with the sacrificial protection of zinc, giving the advantages of both metals. The localised corrosion resistance can be further improved by modifying the coating microstructure, and this can be achieved using laser surface re-melting and rapid solidification. However, one challenge with laser processing of such coatings is their high reflectivity. An understanding of the influence of laser parameters and coating material properties is required to ensure efficient coupling of the laser source and optimum energy absorption. This paper presents some results of the effects of variations in topography, surface microstructure and surface composition on the surface melting characteristics of the coated steel. Scanning electron microscopy, electron dispersive X-ray spectroscopy and surface profilometry are used to examine the effects.Zn-55%Al-1.6%Si coated steel products combine the barrier protection of aluminium with the sacrificial protection of zinc, giving the advantages of both metals. The localised corrosion resistance can be further improved by modifying the coating microstructure, and this can be achieved using laser surface re-melting and rapid solidification. However, one challenge with laser processing of such coatings is their high reflectivity. An understanding of the influence of laser parameters and coating material properties is required to ensure efficient coupling of the laser source and optimum energy absorption. This paper presents some results of the effects of variations in topography, surface microstructure and surface composition on the surface melting characteristics of the coated steel. Scanning electron microscopy, electron dispersive X-ray spectroscopy and surface profilometry are used to examine the effects.