Formation of Al-based amorphous/nanocrystalline coatings by cold spraying

Al-based amorphous/nanocrystalline coatings were prepared by cold spraying. The microstructures and microhardness of the coatings were investigated. The single particle's deposition was prepared and the formation of coatings was discussed. The amorphous content decreased with increased preheating temperature. The main crystalline phase was alpha-Al at preheating temperatures below 400 degrees C, with the appearance of other crystalline phases at 440 degrees C. The porosity values remained in the 3-4% range at different preheating temperatures and the microhardness of coatings decreased as the amorphous content declined. Analysis of the single particle's morphology revealed no obvious jet splashing and some particles at the interface retained near-spherical shape due to inhomogeneous deformation. The interaction of particles with the deposited coatings revealed the importance of alpha-Al because the alpha-Al could promote deformation to some extent. Then three types of interactions of particles with the deposited coatings were put forward. The simulation results about the two particles' interaction confirmed the effect of alpha-Al phase on the coating formation.