Experimental investigation was conducted to explore the formation conditions and provide new insights into the formation mechanisms of the unexplained intermixing phenomenon observed at the substrate-coatings interface of cold sprayed materials. The results indicate that the formation of intermixing interface significantly depends on the extent of plastic deformation at the coating-substrate interface, with severe deformation creating favorable conditions for the intermixing interface. Two factors have been identified to be critical for inducing the severe interfacial plastic deformation: low deposition efficiency and material properties. During low deposition efficiency cold spraying, most of the accelerated particles rebound after impact while inducing accumulative plastic deformation and thus intermixing at the coating-substrate interface. Considering the material properties, the coating materials must have sufficiently high density to attain enough kinetic energy for creating substantial plastic deformation of the first coating layer and the substrate upon their impact. Also, the substrate materials cannot be too hard so that plastic deformation can be induced. Based on the experimental analyses, the hypothesis of the intermixing interface formation mechanism is proposed in this paper.
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