Combining effects of ablation laser and laser preheating on metallic substrates before thermal spraying

Pulsed laser irradiation is a promising approach to remove the contaminant film with a limited damage of the metallic substrate surface. It reduces some serious drawbacks of the traditional means where chemical solvents and aggressive operations are usually employed. But the quality of thermally sprayed coatings depends on a lot of other parameters. The temperature, the wettability and the geometry play important roles in the coating formation and particularly from the adhesion point of view. So, several surface treatments before thermal spraying can be often used in order to obtain good deposits. If the laser ablation effects on metallic substrates are mostly known as well as the substrate temperature impact, the modifications of the surface morphology induced by the combination of laser cleaning and temperature need to be investigated. In this paper, the surface modifications on aluminium 2017 polished substrates induced by laser irradiation at several surface temperatures are proposed and their influence on plasma-sprayed Ni-Al splats was examined. It was confirmed also that a favorable surface condition tends to suppress the splashing and to promote the occurrence of disc-shaped splat.