SURFACE POROSITY FORMATION IN DEPOSITS SPRAYED ONTO FLAT SUBSTRATES BY THE UNIFORM DROPLET SPRAY PROCESS

摘要

The porosity of spray-formed deposits at the substrate interface was investigated by using the uniform droplet spray (UDS) process in two steps. First, the formation of individual splats was analyzed to find the processing conditions for the ideal splat geometry. Second, the effect of multiple-splat interactions on surface porosity formation were studied by comparing splat solidification rate and droplet deposition rate. Experiments were performed with pure tin droplets, 416μm and 271μm in diameter, sprayed onto heated stainless steel and glass substrates. Results showed that slower splat solidification and higher droplet flux reduce surface porosity. A minimum surface porosity of 1.6% was achieved using the UDS process.