Spray casting: an integral model for process understanding and control

Abstract

This paper discusses the scientific and technological aspects of spray casting. An integral model is presented which encompasses and addresses each unit stage of the overall process, namely atomization, spray, consolidation, shape, pre-form solidification and microstructure. The atomization model uses an empirical relationship to correlate the droplet size distribution with spray-forming process parameters. The spray model quantities the condition of the spray upon impact with the substrate; the condition of the spray is represented in terms of the fraction of liquid in the spray and the proportion of solid, mushy and liquid droplets. The sticking efficiency is obtained from the consolidation model and was found to be a critical parameter which governs the yield, shape and microstructure of sprayed deposits. The shape model dynamically predicts the evolution of pre-form shape for different combinations of substrate and spray motion. The model for pre-form solidification uses a two-dimensional heat transfer analysis to compute temperature-liquid fraction profiles in the perform. The microstructure model predicts the final grain or cell size in sprayed deposits as a function of the local solidification time. Individual models are interlinked to identify and asses the effect of critical process parameters on the integrity of spray-cast product.