Improvement of thermal plasma sprayed coating adhesion strength by laser microtexturing of aluminum

Grit blasting and laser processing are two common methods used for surface microtexturing to enhance coating adhesion strength. This paper reports a thermomechanical method of laser microtexturing of Al 7075 alloy using a nanosecond pulsed laser to generate a large increase in surface area. The entire surface area of the substrate was microtextured using laser melting, ablation, and resolidification. The laser microtextured surface morphology consisted of tightly packed pillar-like surface features. The morphology of the microtexture was varied by controlling the laser processing parameters. The laser microtextured surface was coated with metallic particles using a thermal spray process. The tensile adhesive strength of the thermally sprayed metallic coating was higher by over 17% for a 5-mu m deep microtexture, compared to that of grit-blasted samples. Also, this is the highest reported adhesion strength for laser-based microtexturing methods for thermally sprayed bond coatings.