Influence of droplet size and ejection frequency on molten pool dynamics and deposition morphology in TIG-aided droplet deposition manufacturing

Abstract

Droplet parameters like diameter and ejection frequency are identified as essential factors in metal-based droplet deposition manufacturing (DDM). A high-fidelity multi-physics model was developed to reproduce the improved DDM process (previously proposed as tungsten inert gas (TIG) - aided DDM) where multiple metal droplets merge with a moving molten pool to form a single track. This paper mainly discusses the influence of droplet parameters on the molten pool behaviors and deposition morphology. Two droplet sizes with different generation frequency were included in the model: high-frequency small droplet and low-frequency large droplet, however, the volume flow rate of the two cases remains same. During deposition, the significant fish-scale ripples on the top surface of deposited layers occurred from the smaller droplets into the larger ones through partial coalescence. For high-frequency small droplet mode, the shape of deposited layer is more beautiful with the surface being continuous, smooth and even. Because of differences in the physical processes involved, the relationship between droplet size mode and deposition morphology was further elaborated based on the molten pool configuration. This work provides a perspective in understanding the physical phenomena involved in TIG-aided DDM and lays the foundation for the optimization of surface macro-quality of deposits.