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Process porosity and mechanical performance of fused filament fabricated 316L stainless steel

James Damon (Institute for Applied Materials IAM-WK, Karlsruhe Institute of Technology, Karlsruhe, Germany)
Stefan Dietrich (Institute for Applied Materials IAM-WK, Karlsruhe Institute of Technology, Karlsruhe, Germany)
Sasidhar Gorantla (Apium Additive Technologies GmbH, Karlsruhe, Germany)
Uwe Popp (Apium Additive Technologies GmbH, Karlsruhe, Germany)
Brando Okolo (Apium Additive Technologies GmbH, Karlsruhe, Germany)
Volker Schulze (Institute for Applied Materials IAM-WK, Karlsruhe Institute of Technology, Karlsruhe, Germany)

Rapid Prototyping Journal

ISSN: 1355-2546

Article publication date: 15 August 2019

Issue publication date: 30 August 2019

Abstract

Purpose

This study aims to investigate the correlation between build orientation characteristics, part porosity and mechanical properties of the fused filament fabrication (FFF) process to provide insight into pore formation mechanisms and to establish guidelines for optimal process configurations.

Design/methodology/approach

Micro computed tomography and metallographic sections provide the basis for a correlation between porosity and extrusion path. Using the correlations found in this study, the way to improve printing strategies and filament properties can be deduced directly from an analysis of the print path and the final influence on mechanical performance.

Findings

With metal-FFF 3D printing technology, near-dense parts (0.5 Vol.%) can be fabricated. The pore architecture is strongly connected to the build direction and print strategy with parallel, elongated pore channels. Mechanical values of FFF samples are similar to metal injection-molded (MIM) parts, except the elongation to fracture. The high difference of yield strength of sintered samples compared to laser powder bed fusion (LPBF) samples can be attributed to the finer grains and a Hall–Petch hardening effect. The conclusions derived from this study are that the presented process is capable of producing comparable part qualities compared to MIM samples, with higher build rates in comparison to LPBF processes.

Originality/value

316L stainless steel was successfully manufactured via FFF. This paper also addresses the effects of scanning strategies on the resulting porosity and proposes improvements to reduce residual porosity, thus increasing the mechanical performance in the future.

Keywords

Acknowledgements

The authors kindly thank Dr Ing. Daniel Schliephake for his work on sample preparation and scanning electron microscopy analysis.

Citation

Damon, J., Dietrich, S., Gorantla, S., Popp, U., Okolo, B. and Schulze, V. (2019), "Process porosity and mechanical performance of fused filament fabricated 316L stainless steel", Rapid Prototyping Journal, Vol. 25 No. 7, pp. 1319-1327. https://doi.org/10.1108/RPJ-01-2019-0002

Publisher

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Emerald Publishing Limited

Copyright © 2019, Emerald Publishing Limited