Numerical Simulation And Experimental Study Of Constrained Spray Deposition Process

Spray Conform as a new rapid solidification technique,is widely used in recent years for the researching and processing of many kinds of metallic materials with excellent properties.The technique integrates the best aspect of spray forming technology and has a wide application prospect.Due to the complexity of Spray forming technology and continuous extrusion technology and many process parameters,this paper adopts the flow controller to restrain the atomized jet to simulate the atomized process.Through the comparison of numerical simulation and the result of experiment,the influence of processing parameters are investigated systematically and laid the foundations for the production of high alloy material.The gas flow field of the atomizer with ring holes or circular seam is analyzed using the RNG κ-ε turbulence model,TAB model and DPM model in the CFD software Fluent.The results show that the atomizer with ring holes forms semi-closed pressure area when the other parameters are the same,in which the pressure of the inner melt is smaller and the velocity at the center of holes is larger,thus providing stronger crushing ability of liquid column.And it is more suitable for spray Conform.By comparing the gas flow fields from five kinds of free atomizer with different air outlet angles,we find that in order to increase the atomization effect and reduce the influence of the eddy current area and the internal melt pressure of the draft tube,the best angle of the atomizer outlet angle is 25°.By comparing the gas flow fields under five different gas inlet pressures between the traditional free spray forming and constraint spray forming,we find the droplet spreads fan-wise and inclines to one side,which are in agreement with the experimental results.The velocity attenuation is evident throughout the process.When the gas inlet pressure is 0.25MPa,there is no obvious oxidation of deposit,and the deposit can just match with the extrusion wheel of continuous extrusion machine.The deformation and crushing of droplet in the flow field is analyzed.The numerical results show that the static pressure field and velocity distribution are not uniform at the front and rear stagnation point of droplet.Moreover,the less evenly distribution the static pressure on the surface of the droplet is caused by the larger relative velocity,which leads to the deformation or even crushing of droplet.The spreading process of the droplet on three kinds of inclined wall have been analyzed in the paper.It is found that,forward speed along the wall is faster than backward,and backward speed along the wall reduce to 0 in the droplet spreading,with the increase of the tilt angle from 0° to 60°.The contact between the droplet and the wall is increased.The possibility of forming an porosity is reduced.The solidified edge of the molten metal is not easy to curl inward and the coating is more uniform,which is basically consistent with experiment results.