Influence of Pulsed Laser Ablation Parameters on Adhesion of Cold Spray Al 6061 Coatings on Extruded Al 6061 Substrates

The effect of pulsed laser ablation as a substrate pretreatment technique on the adhesive strength of cold-sprayed Al6061 coatings deposited onto extruded Al6061 substrates was investigated. The influence of laser ablation parameters on the surface morphology and roughness of extruded Al 6061 substrates were systematically examined. A Nd:YAG pulsed laser (1.064 µm, 12 ns, 30 Hz) was employed with fluences ranging from 1.55 to 3.53 J/cm² and surface coverages between 5.8 × and 109.6 ×. Distinct morphological evolution stages were observed, progressing from irradiated and dimpled textures at low laser exposures to cauliflower-like structures at higher exposures. This transformation was primarily governed by cumulative surface coverage resulting from overlapping laser passes, indicating that surface coverage plays a more dominant role than fluence in driving morphological changes. Surface texturing emerged at a threshold of approximately 8.4 × coverage. Cold spray deposition was subsequently performed on the laser-textured substrates and compared to coatings prepared using conventional pretreatments, including grit blasting and degreasing. Adhesion strength was assessed via two mechanical testing methods (ASTM C633 and a modified ASTM E8). Laser texturing produced substantial improvements in coating adhesion, with increases of up to 242% relative to grit-blasted substrates. A maximum bond strength of 90 MPa was achieved at a fluence of 3.53 J/cm² and 8.4 × surface coverage. These findings demonstrate that controlled laser ablation can effectively tailor surface morphology to significantly enhance the adhesion performance of cold-sprayed Al 6061 coatings.