Effect of particle size, morphology, and hardness on cold gas dynamic sprayed aluminum alloy coatings

This work describes recent progress in Cold Gas Dynamic Spraying process of conventional and nanocrystalline 2618 (Al–Cu–Mg–Fe–Ni) aluminum alloy containing Sc. As-atomized and cryomilled 2618+Sc aluminum powders were sieved in two ranges of particle size (below 25 μm and between 25 and 38 μm), and sprayed onto aluminum substrates. The mechanical behavior of the powders and the coatings was studied using the nanoindentation technique, while the microstructure was analyzed using scanning and transmission electron microscopy. The influence of the powder microstructure, morphology and behavior during deposition on the coating properties was analyzed. It was concluded that the hard cryomilled particles do not experience extensive plastic deformation, and therefore failed to form a coating as dense as those produced using the gas-atomized spherical powder, despite the fact that the irregular shape cryomilled particles presented higher flight and impact velocities than the gas-atomized spherical particles. It was also observed that the influence of the particle morphology on the particle velocities is more pronounced for the larger particle size range (between 25 and 38 μm).