Processing Conditions Affecting Grain Size and Mechanical Properties in Nanocomposites Produced via Cold Spray
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P. Cavaliere, A. Perrone, and A. Silvello (Submitted October 4, 2013; in revised form February 25, 2014) Cold spray is a coating technology based on aerodynamics and high-speed impact dynamics. In this process, spray particles (usually 1-50 lm in diameter) are accelerated to a high velocity (typically 300-1200 m/s) by a high-speed gas (pre-heated air, nitrogen, or helium) flow that is generated through a convergent-divergent de Laval-type nozzle. A coating is formed through the intensive plastic deformation of particles impacting on a substrate at a temperature below the melting point of the spray material. 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 process parameters on grain refinement and mechanical properties were analyzed for composite particles of Al-Al2O3, Ni-BN, Cu-Al2O3, and Co-SiC. The properties of the formed nanocomposites were compared with those of the parent materials sprayed under the same conditions. The process conditions, leading to a strong grain refinement with an acceptable level of the deposit mechanical properties such as porosity and adhesion strength, are discussed.
Keywords
cold spray, mechanical properties, microstructural behavior, nanocomposites, processing parameters
1. Introduction
unique. Cold spray can potentially provide functionalities such as restoration, sealing, surface modification, wear resistance, thermal barriers, heat dissipation, rapid prototyping, aesthetic coatings, and fatigue resistance, without the undesirable effects of process temperatures or metallurgical incompatibilities between materials. It can also be used to increase the heat resistance of a material. Cold spray technology appears to be promising in the production of nanostructured composites due to the possibility of depositing fine particles materials and of tuning the final properties by modifying the process parameters that lead to severe plastic deformation. The potential of preparing cold sprayed nanostructured composites is largely described in references (Ref 3, 4). The advantage of cold sprayed coatings with regards to corrosion resistance is shown in references (Ref 5, 6). References 7-9 describe the microstructural behavior of the deposited material by varying the reinforcing particle dimensions. The effect of post spray heat treatment on the microstructural and mechanical properties of deposits is largely described in Ref 10 and 11. The strengthening mechanisms acting in cold spray nanocomposites are described in Ref 12. The present paper focuses on the microstructural and mechanical behavior of nanocomposites produced by varying process parameters to optimize adhesion strength, grain refinement, and porosity reduction of the deposited materials.
Cold spraying is a coating technology based on aero and high-speed impact dynamics of small particles [usually 1-50 lm in diameter (Ref 1)]. A coating is formed through the intensive plastic deformation of particles impactin
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