Grain refinement of Al coatings via in-situ shot-peening assisted cold spray

In this study, pure Al coatings were deposited via in-situ shot-peening assisted cold spray in order to study the effect of the in-situ tamping effect which caused by the impact of large sized SP particles on grains size evolution of coatings. The comprehensive microstructure analysis of the as-sprayed Al coatings was carried out using SEM, EBSD and XRD. A commercial gas atomized Al powder with a grain size range of 10-20 μm was used as the spraying powder. The cross section of the as-sprayed Al particles present elongated rectangular indicates that the nearly spherical particles experienced severe plastic deformation by the impact of large sized SP particles. Dynamic recrystallization of dislocations-ridden regions was responsible for the grain refinement of cold sprayed coating. Aluminum grains with size of several tens to several hundred of nanometers can be apparently recognized at the whole cross section of the particle. In-situ shot-peening assisted cold spray technique can deposit completely nanocrystalline coating using micrometer-grain powder thus be deployed to develop high quality coatings of commercial importance.