Molten droplet solidification and substrate remelting in microcasting Part II: Parametric study and effect of dissimilar materials

Abstract

This paper presents a parametric study of relevant processing parameters found in microcasting Shape Deposition Manufacturing (SDM). Microcasting SDM is a novel, layered manufacturing process capable of rapidly manufacturing near net shape, metal objects. The quality of artifacts built with this process depends on proper metallurgic bonding between impacting molten droplets and previously deposited substrate layers, as well as on the final microstructure of the artifact. Numerical simulations are performed to investigate the effect of operating conditions on the metallurgic bonding induced by substrate remelting and on the microstructure determined by the cooling rates during solidification. Particularly, the effect of droplet impinging temperatures, substrate initial temperatures and combinations of copper and stainless steel materials are investigated. Numerical predictions reveal that impinging droplet temperature variations, within the attainable range in microcasting SDM, have a minimal effect on the cooling rates during solidification. However, droplet temperature has a significant effect on the substrate remelting depth. Furthermore, this investigation quantifies the extent to which substrate preheating lowers the cooling rate during solidification and promotes substrate remelting. The study of the interaction between copper and stainless steel materials shows that the cooling rates during solidification of the deposition material and the occurrence of substrate remelting are both highly dependent on the combination of materials.