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Title: Effect of laser power on defect, texture, and microstructure of a laser powder bed fusion processed 316L stainless steel

Abstract

The effect of laser power on defect characteristics, microstructure development, constituent phases, and crystallographic texture was studied on a laser powder bed fusion (L-PBF) processed 316L stainless steel. A series of cylindrical specimens were additively manufactured as a function of laser power ranging from 380 to 200W with a fixed scan speed of 300 mm/s using a selective laser melting system. The density (in terms of count, surface area, and porosity), size (mean values of major axis length, surface area, and volume), shape (aspect ratio and sphericity), and orientation (in terms of the angle between the major axis and build direction) of macroscopic defects in as-printed L-PBF cylinders were characterized using high-resolution synchrotron x-ray computed microtomography with a 0.65μm resolution. Moreover, the changes in the preferred crystallographic orientations and constituent phases were investigated using high-energy synchrotron x-ray diffraction. Finally, the melt pool shape and grain size/orientation were analyzed using metallography. The results show that the porosity increases linearly from 0.13 to 0.88% with the decrease in laser power. However, even with the decrease in laser power by about half and corresponding seven-fold increase in porosity, the 200W case can still be considered as nearly fully dense. On the other hand,more » with the same decrease in the laser power, the melt pool size/shape, grain size, and texture changed significantly. In conclusion, the role of energy input in the simultaneous changes in defect properties and microstructure development will be discussed.« less

Authors:
ORCiD logo; ; ; ORCiD logo; ; ; ORCiD logo; ;
Publication Date:
Research Org.:
Oak Ridge Y-12 Plant (Y-12), Oak Ridge, TN (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Scientific User Facilities Division
OSTI Identifier:
1504438
Alternate Identifier(s):
OSTI ID: 1477038; OSTI ID: 1493501
Report Number(s):
IROS6359; IROS7659
Journal ID: ISSN 0264-1275
Grant/Contract Number:  
NA0001942; AC02-06CH11357
Resource Type:
Accepted Manuscript
Journal Name:
Materials & Design
Additional Journal Information:
Journal Volume: 164; Journal Issue: C; Journal ID: ISSN 0264-1275
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; synchrotron; tomography; diffraction; stainless steel; additive manufacturing; selective laser melting; porosity; defects; texture

Citation Formats

Choo, Hahn, Sham, Kin-Ling, Bohling, John, Ngo, Austin, Xiao, Xianghui, Ren, Yang, Depond, Philip J., Matthews, Manyalibo J., and Garlea, Elena. Effect of laser power on defect, texture, and microstructure of a laser powder bed fusion processed 316L stainless steel. United States: N. p., 2019. Web. doi:10.1016/j.matdes.2018.12.006.
Choo, Hahn, Sham, Kin-Ling, Bohling, John, Ngo, Austin, Xiao, Xianghui, Ren, Yang, Depond, Philip J., Matthews, Manyalibo J., & Garlea, Elena. Effect of laser power on defect, texture, and microstructure of a laser powder bed fusion processed 316L stainless steel. United States. doi:10.1016/j.matdes.2018.12.006.
Choo, Hahn, Sham, Kin-Ling, Bohling, John, Ngo, Austin, Xiao, Xianghui, Ren, Yang, Depond, Philip J., Matthews, Manyalibo J., and Garlea, Elena. Fri . "Effect of laser power on defect, texture, and microstructure of a laser powder bed fusion processed 316L stainless steel". United States. doi:10.1016/j.matdes.2018.12.006. https://www.osti.gov/servlets/purl/1504438.
@article{osti_1504438,
title = {Effect of laser power on defect, texture, and microstructure of a laser powder bed fusion processed 316L stainless steel},
author = {Choo, Hahn and Sham, Kin-Ling and Bohling, John and Ngo, Austin and Xiao, Xianghui and Ren, Yang and Depond, Philip J. and Matthews, Manyalibo J. and Garlea, Elena},
abstractNote = {The effect of laser power on defect characteristics, microstructure development, constituent phases, and crystallographic texture was studied on a laser powder bed fusion (L-PBF) processed 316L stainless steel. A series of cylindrical specimens were additively manufactured as a function of laser power ranging from 380 to 200W with a fixed scan speed of 300 mm/s using a selective laser melting system. The density (in terms of count, surface area, and porosity), size (mean values of major axis length, surface area, and volume), shape (aspect ratio and sphericity), and orientation (in terms of the angle between the major axis and build direction) of macroscopic defects in as-printed L-PBF cylinders were characterized using high-resolution synchrotron x-ray computed microtomography with a 0.65μm resolution. Moreover, the changes in the preferred crystallographic orientations and constituent phases were investigated using high-energy synchrotron x-ray diffraction. Finally, the melt pool shape and grain size/orientation were analyzed using metallography. The results show that the porosity increases linearly from 0.13 to 0.88% with the decrease in laser power. However, even with the decrease in laser power by about half and corresponding seven-fold increase in porosity, the 200W case can still be considered as nearly fully dense. On the other hand, with the same decrease in the laser power, the melt pool size/shape, grain size, and texture changed significantly. In conclusion, the role of energy input in the simultaneous changes in defect properties and microstructure development will be discussed.},
doi = {10.1016/j.matdes.2018.12.006},
journal = {Materials & Design},
number = C,
volume = 164,
place = {United States},
year = {2019},
month = {2}
}

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