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Effect of Direct Energy Deposition Process Parameters on Single-Track Deposits of Alloy 718

1
Department of Engineering Science, University West, 46186 Trollhättan, Sweden
2
Department of Materials and Manufacturing, Jönköping University, 55111 Jönköping, Sweden
*
Author to whom correspondence should be addressed.
Metals 2020, 10(1), 96; https://doi.org/10.3390/met10010096 (registering DOI)
Received: 5 December 2019 / Revised: 3 January 2020 / Accepted: 5 January 2020 / Published: 7 January 2020
(This article belongs to the Special Issue Metal Deposition Technologies)
The effect of three important process parameters, namely laser power, scanning speed and laser stand-off distance on the deposit geometry, microstructure and segregation characteristics in direct energy deposited alloy 718 specimens has been studied. Laser power and laser stand-off distance were found to notably affect the width and depth of the deposit, while the scanning speed influenced the deposit height. An increase in specific energy conditions (between 0.5 J/mm2 and 1.0 J/mm2) increased the total area of deposit yielding varied grain morphologies and precipitation behaviors which were comprehensively analyzed. A deposit comprising three distinct zones, namely the top, middle and bottom regions, categorized based on the distinct microstructural features formed on account of variation in local solidification conditions. Nb-rich eutectics preferentially segregated in the top region of the deposit (5.4–9.6% area fraction, Af) which predominantly consisted of an equiaxed grain structure, as compared to the middle (1.5–5.7% Af) and the bottom regions (2.6–4.5% Af), where columnar dendritic morphology was observed. High scan speed was more effective in reducing the area fraction of Nb-rich phases in the top and middle regions of the deposit. The <100> crystallographic direction was observed to be the preferred growth direction of columnar grains while equiaxed grains had a random orientation. View Full-Text
Keywords: laser metal deposition (LMD); columnar dendritic morphology; constitutional supercooling; columnar to equiaxed transition (CET); high deposition rate laser metal deposition (LMD); columnar dendritic morphology; constitutional supercooling; columnar to equiaxed transition (CET); high deposition rate
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Sreekanth, S.; Ghassemali, E.; Hurtig, K.; Joshi, S.; Andersson, J. Effect of Direct Energy Deposition Process Parameters on Single-Track Deposits of Alloy 718. Metals 2020, 10, 96.

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