Influence of Pulsed Laser Ablation Parameters on Adhesion of Cold Spray Al6061 Coatings on Extruded Al6061 Substrates

This study investigates the influence of laser ablation parameters on the adhesion of cold Spray (CS) Al6061 coatings on extruded Al6061 substrates. A Nd:YAG laser (1064 nm, 30 Hz) was used with fluences between 1.55-3.53 J/cm² and repetition counts ranging from 7 to -100 X.

The effect of fluence and repetition counts on surface roughness, microstructure, and adhesion were investigated using laser profilometry, SEM, EDS, and optical microscopy. Two mechanical testing methods (ASTM C633 and a custom tensile test) were utilized to assess adhesion strength. The results demonstrated that average surface roughness (Ra) varied from 0.4 to 2.2mm with increasing fluence and repetition counts. Optimal conditions for laser ablation were observed in the 7-14 x repetition count range. In comparison to conventional degreased and grit-blasted surfaces, a 145% increase in tensile strength and 71% increase in shear strength were observed under optimal conditions. However, excessive laser texturing (>38μm depth) compromised adhesion. The study concluded that optimized laser ablation enhances adhesion in cold-sprayed Al6061 coatings, offering the potential for developing variable cross-section extruded beams in the transportation industry.