Mechanical and microstructural behavior of nanocomposites produced via cold spray

Cold spraying is an innovative coating technology mainly based on the high speed impact of metals and ceramic particles on different substrates. Through the employment of low temperature gases (Air, He, N2) spray particles (usually 1-50 μm in diameter) are accelerated to a high velocity (typically 300-1200 m/s) that is generated through a convergent-divergent de Laval type nozzle. Severe plastic deformation of particles impacting on the substrate occurs at temperature well below the melting point leading to the unique mechanical properties experienced by such kinds of coatings. In the present paper the main processing parameters affecting the microstructural and mechanical behavior of metal-metal cold spray deposits are described. The effect of processing parameters on grain refinement and mechanical properties were analyzed for different particles (Ti-TiAl3, Al-Al2O3, Ni-Cr3C2, Ni-BN, Cu-Al2O3, Co-SiC). The results belonging to the properties of the formed nanocomposites were compared with those of the pure parent materials sprayed in the same conditions. Many experimental conditions have been analyzed in terms of particle dimensions and composition, substrate temperature and composition, gas temperature and pressure, nozzle properties. In particular, those conditions leading to a strong grain refinement with an acceptable level of the mechanical deposit properties such as porosity, adhesion strength and hardness were underlined.