Deposition Behavior and Microstructure of Cold-Sprayed Ni-Coated Al Particles

Cold spraying is a novel technology for preparing solid-state coatings. Single Ni-coated Al particles were deposited onto different substrates by cold spraying at different accelerating gas temperatures, as well as preparing for the coatings. The influence of the accelerating gas temperature and substrate microhardness on the particle deposition deformation, microstructure, and microhardness of Ni-coated Al coatings were investigated. The results show that the embedding depth of Ni-coated Al particles into the Al substrate increased with increasing the accelerating gas temperature. However, the cold-sprayed Ni-coated Al particles did not embed into the Q235 steel substrate, and the degree of plastic deformation of the Ni-coated Al particles increased with increasing the accelerating gas temperature. Moreover, the morphology of the Ni-coated Al splat deposited onto the Q235 steel substrate at an accelerating gas temperature of 400 °C presented a flattened morphology, which was different from the nearly spherical or ellipsoidal morphology of the Ni-coated Al feedstock. Ni-coated Al coatings exhibited the same phase compositions as the feedstock powders, and the Ni and Al phases in the coatings incurred a certain plastic deformation. Compared with the Q235 steel substrate, an Al substrate with a lower microhardness is beneficial for forming the first layer coating, as well as for the formation of an intermixing structure between the Ni-coated Al coating and Al substrate. The porosity of Ni-coated Al coatings decreased and the thickness increased when increasing the gas temperature; in particular, the coating deposited onto Al substrate had the lowest porosity and the largest thickness at an accelerating gas temperature of 400 °C. Meanwhile, the microhardness of the coating deposited onto the Al substrate was higher than that deposited onto the Q235 steel substrate under the same cold spraying conditions.