On the topographic and energetic surface modifications induced by laser treatment of metallic substrates before plasma spraying

Abstract

Laser surface cleaning has been proven as a very suitable technique for the substitution of some surface preparation steps, such as wet cleaning and grit blasting. The mechanisms involved in short pulsed laser ablation include the absorption of the laser light and conversion into heat via collisional processes. Ejection of matter is achieved either by direct vaporization or hydrodynamical sputtering. This article aims at clarifying the laser–matter interaction mechanisms and effects on metallic materials for different surfaces initial roughness and laser beam energy densities. Both topographic and energetic modifications are investigated by SEM observations, roughness characterization and wettability measurements. Increasing fluences leads to a crater formation, which can cover the whole-irradiated area, but without any important contribution on surface roughness. Observed pattern can be correlated to the melting of the irradiated area and preferential absorption. Improvements of wetting can be observed after laser treatment despite the limitations of the sessile drop technique.