Influence of Laser Surface Preparation on Adhesion of Thermally Sprayed Coatings

Abstract

Laser treatment was used to prepare substrate surfaces for thermal spray deposition. The interaction between aluminium and titanium alloys and short Nd: YAG laser pulses was investigated. In particular, the topography of laser treated surfaces has been observed and analysed using scanning electron microscopy, atomic force microscopy, and laser profilometry. The coating/substrate adhesion was quantified for various surface preparation parameters by means of tensile tests and Rockwell indentations for Al₂O₃–13 wt-%TiO₂ coatings. The influences of the laser energy density and the time interval between the laser treatment and the plasma spraying were studied. Compared with conventional degreasing and grit blasting, laser treatment produces better adhesion. The mechanisms of adhesion after laser treatment were investigated by transmission electron microscopy and electron energy loss spectrometry for a pure copper coating on a pure aluminium substrate. It appears that the adhesion is owing to metallurgical bonding.