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

• Published in: Materials & design Vol. 225; p. 111534
• Main Authors: Liu, Zixin, Yang, Yongqiang, Han, Changjun, Zhou, Hanxiang, zhou, Heng, Wang, Meng, Liu, Linqing, Wang, Han, Bai, Yuchao, Wang, Di
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.2023; Elsevier
• Subjects: Image processing; Laser powder bed fusion; Spatter dynamics; Spatter features; Statistical analysis; Laser powder bed fusion; Statistical analysis; Image processing; Spatter features; Spatter dynamics
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2022.111534

[Display omitted] •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.•The droplet spatter features and dynamics exhibited a strong correlation with the gas flow velocity.•The median of the spattering angle under normal melting is around 40° under the SD-A condition and about 60° under the SD-W condition.•With the increase of gas velocity, the spattering angle became smaller, the quantity of micro-spatter increased, and the maximum spattering speed of the spatter became higher — up to 12.8 m/s at 2.5 m/s gas velocity.•The droplet spatter behavior influenced by gas flow parameters are concluded to three ways: gas flow induced, vapor driven, and melt pool extrusion, presented in backside, upper, and frontside relative to the melt pool. 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.