Formation of 'Super Plastic Agglomerate Mixing' (SPAM) Between Copper and 6061-T6511 Aluminum Deposited by the Supersonic Particle Deposition Process (SPD)

摘要

Supersonic Particle Deposition (SPD) is a process whereby metal powder particles are utilized to form a coating by means of ballistic impingement upon a suitable substrate. The metal powders range in particle size from <5 -50 microns and are accelerated by a supersonic (300-1000 m/s) stream of compressed gas. The spray nozzle design incorporates the use of a converging-diverging throat through which a preheated gas stream is expanded to attain supersonic velocities, with an accompanying decrease in temperature. The term "cold spray" has been used to describe this process due to the relatively low temperatures (0-500℃) of the expanded gas particle stream that exits the nozzle, but within the context of this paper the process will be referred to as 'Supersonic Particle Deposition' or SPD, which the authors feel best describe this process. The adhesion of the metal powder to the substrate, as well as the cohesion of the deposited material, is accomplished in the solid state and the characteristics of the SPD deposit are quite unique, having significant advantages over thermal spray methods. The SPD process does not use thermal energy to melt the particles to be deposited, but instead relies upon the supersonic impact of the particles on the substrate, which plastically deform and cause cratering. The bonding mechanism of SPD has been theorized to be analogous to that of explosive welding, whereas the formation of a solid-state jet of metal occurs at the impact point between the particle and the substrate. The objective of this paper is to present microstructural evidence of such a bonding mechanism, introduced as 'Super Plastic Agglomerate Mixing' (SPAM), between copper and A16061-T6511 deposited by SPD. Measurements of adhesion strength, hardness and density of the SPD coating are included and the process parameters that are required to produce SPAM will also be discussed.