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Abstract
The porosity in the spray deposited material is studied through a mathematical model. In the model, the transport of momentum and heat between the falling droplet and the atomising gas in axial and radial direction is coupled with the packing density of spherical shape particles to determine the porosity in the spray deposited material. The effect of plenum pressure, deposition distance, melt superheat, melt flowrate and radial spreading of the spray on the porosity formation is studied. The variation in the porosity is explained on the basis of mechanism of porosity formation and the proportion of solid/liquid fraction in the spray. Porosity is also measured by performing experiments on spray deposition of aluminium on copper substrate. The measured porosity is found to be slightly higher than the calculated one. The discrepancy is explained on the basis of the microstructure of the spray deposited aluminium.