Effects of gas flow parameters on droplet spatter features and dynamics during large-scale laser powder bed fusion

The droplet spatters generated by the laser induction directly affect the processing quality of the laser powder bed fusion (LPBF) process, gas parameters are a key factor in this process. In this work, the formation characteristics and dynamic behavior of process-by-products under different gas flow parameters were presented through high-speed imaging. A novel image processing method and spatters feature extraction algorithm were used to obtain the spatter number, the total spatter area, the spattering angle and the spattering velocity of 8 scenarios. With the comparative analysis, scan direction against the gas flow (SD-A) is proved to produce fewer droplet spatters than scan direction with the gas flow (SD-W), and the quantitative relationship between the gas flow parameters and the droplet spatter behavior is established for the first time. The maximum spattering velocity increases to 12.8 m/s as the gas flow velocity rise to 2.5 m/s. Finally, the mechanisms of the droplet spatter behavior influenced by gas flow parameters are discussed. The work provides a theoretically reference for the design and control of gas flow parameters during the large-scale LPBF.