High deposition rate approach of selective laser melting through defocused single bead experiments and thermal finite element analysis for Ti-6Al-4V

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Abstract

Selective laser melting (SLM) is a commonly used powder bed fusion metal additive manufacturing (AM) process. Although SLM is preferred due to its near-net-shape part commitment, the deposition rate of this process is slower compared with alternative metal processes. A higher deposition rate of SLM can be obtained by increasing the laser scanning velocity and laser power; however, this results in decreased part quality due to the SLM process's physical limits. This study presents the conditions for a higher deposition rate for various process parameters with defocused beams to eliminate the void defects due to keyholing formed in the melt pool. Single bead experiments were conducted, and the thresholds of the process parameters resulting in voids were identified. A melt pool depth-to-width ratio of 0.85 was found to be a critical value for preventing voids in the process. The melt pool aspect ratio was related with the process parameters by using the normalized enthalpy and the volumetric energy density. The threshold values of the normalized enthalpy due to voids were independent from the beam diameters. Moreover, unstable single bead track thresholds were plotted as a function of the beam diameters. In addition to the experiments, a finite element analysis model was built with calibrated absorptivity and heat source parameters to predict the melt pool geometries for a wide range of process parameters (power = 100–370 W, velocity = 200–2000 mm/s, and beam diameter = 100–260 μm).

Original languageEnglish
Article number100984
JournalAdditive Manufacturing
Volume31
DOIs
Publication statusPublished - Jan 2020

Bibliographical note

Publisher Copyright:
© 2019

Funding

The author thanks Prof. Ebubekir Koc and Mr. Mert Coskun at Fatih Sultan Mehmet University for their assistance in conducting the SLM experiments. In addition, the author thanks Mr. Semih Guven at Marmara University for helping to prepare the cross-sectioned samples. The author appreciates the guidance of Dr. Michael Gouge and Prof. Sualp Ozel on the Netfabb Simulation practices. The author gratefully acknowledges The Scientific and Technological Research Council of Turkey (TÜBİTAK) through Project No: 216M033 for their financial support. Finally, the author thanks David Yunkunis, Kerem Dogan and Hakan Gunaydin for proofreading the article. The author thanks Prof. Ebubekir Koc and Mr. Mert Coskun at Fatih Sultan Mehmet University for their assistance in conducting the SLM experiments. In addition, the author thanks Mr. Semih Guven at Marmara University for helping to prepare the cross-sectioned samples. The author appreciates the guidance of Dr. Michael Gouge and Prof. Sualp Ozel on the Netfabb Simulation practices. The author gratefully acknowledges The Scientific and Technological Research Council of Turkey (TÜBİTAK) through Project No: 216M033 for their financial support. Finally, the author thanks David Yunkunis, Kerem Dogan and Hakan Gunaydin for proofreading the article.

FundersFunder number
Türkiye Bilimsel ve Teknolojik Araştırma Kurumu216M033
Marmara Üniversitesi

    Keywords

    • Additive manufacturing
    • Defocused beam
    • Deposition rate
    • Finite element analysis
    • Selective laser melting

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