Direct Observation of Pore Formation Mechanisms during LPBF Additive Manufacturing Process and High Energy Density Laser Welding
Laser powder bed fusion (LPBF) is a 3D printing technology that can print parts with complex geometries that are unachievable by conventional manufacturing technologies. However, pores formed during the printing process impair the mechanical performance of the printed parts, severely hindering their widespread application. Here, we report six pore formation mechanisms that were observed during the LPBF process. Our results reconfirm three pore formation mechanisms - keyhole induced pores, pore formation from feedstock powder and pore formation along the melting boundary during laser melting from vaporization of a volatile substance or an expansion of a tiny trapped gas. We also observe three new pore formation mechanisms: (1) pore trapped by surface fluctuation, (2) pore formation due to depression zone fluctuation when the depression zone is shallow and (3) pore formation from a crack. The results presented here provide direct evidence and insight into pore formation mechanisms during the LPBF process, which may guide the development of pore elimination/mitigation approaches. Since certain laser processing conditions studied here are similar to the situations in high energy density laser welding, the results presented here also have implications for laser welding.
S. M. Hojjatzadeh et al., "Direct Observation of Pore Formation Mechanisms during LPBF Additive Manufacturing Process and High Energy Density Laser Welding," International Journal of Machine Tools and Manufacture, vol. 153, Elsevier Ltd, Jun 2020.
The definitive version is available at https://doi.org/10.1016/j.ijmachtools.2020.103555
Mechanical and Aerospace Engineering
Keywords and Phrases
Additive manufacturing; Laser powder bed fusion; Laser welding; Pore formation; X-ray imaging
International Standard Serial Number (ISSN)
Article - Journal
© 2020 Elsevier Ltd, All rights reserved.
01 Jun 2020