Effect of substrate surface preparation on cold sprayed Al-Zn-Al2O3 composite coating properties

In this study, a powder mixture containing Al-Zn and Al2O3 particles on AA6083 aluminum alloy was coated by the cold spray method. In order to investigate the effect of the substrate surface properties on the composite coating structure obtained by the cold spray process, the substrate surface was prepared by grit blasting and shot peening. It was found that Al and Zn particles in the coatings of all samples flattened near the substrate surface regions due to the deformation effect. But, Zn particles, because of their low hardness in contrast to the shot peened surface fragmented near the material surface regions through the impact. Similarly, the size of the Al2O3 particles decreased incrementally from the coated surface to the substrate. Particularly in the shot peened samples, the size of the Al2O3 particles decreased by striking the hard substrate surface and fracturing more. Moreover, the amount of Al2O3 particles in the substrate surface of all samples was lower as the particles rebounded. It was also found that pore formation in the coating layer of all samples was very limited. Pore formation in the shot peened samples was by contrast lower than in the grit blasted samples. In addition, a very low oxide layer was found between the particles in the upper region of both the grit blasted and shot peened samples' coating layer.