Title

Direct Observation of Pore Formation Mechanisms during LPBF Additive Manufacturing Process and High Energy Density Laser Welding

Abstract

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.

Department(s)

Mechanical and Aerospace Engineering

Comments

This work is funded by the Department of Energy's Kansas City National Security Campus Managed by Honeywell Federal Manufacturing & Technologies (FM&T) and National Science Foundation.

Keywords and Phrases

Additive manufacturing; Laser powder bed fusion; Laser welding; Pore formation; X-ray imaging

International Standard Serial Number (ISSN)

0890-6955

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2020 Elsevier Ltd, All rights reserved.

Publication Date

01 Jun 2020

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