Effect of powder morphology on the microstructure and properties of cold sprayed Ni coatings

Cold sprayed Ni coatings offer new possibilities for repairing damaged and mis-machined components. The morphology of the powder particles and grain-size distribution have a significant influence on the particles' behaviour during compaction and on the properties of the coating. In this study, two Ni powders with different morphology and grain-size distribution were cold sprayed on a 7075 Al alloy substrate. The first powder, Ni HR, had an irregular spherical shape, whereas the second, Ni E, possessed a dendritic shape. SEM and TEM investigations revealed differences in the microstructure and properties of the Ni cold-sprayed coatings. The coating sprayed using the dendritic powder revealed enhanced mechanical properties and the surface had half the roughness of the Ni coatings deposited using the irregular spheroidal powder.