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Title: Residual stress determination of direct metal laser sintered (DMLS) inconel specimens and parts

Abstract

Residual stress determinations and microstructural studies were performed on a series of Inconel 718Plus prisms built using Direct Metal Laser Sintering (DMLS) at Honeywell Aerospace (hereafter also referred to as Honeywell). The results are being used to validate and improve existing models at Honeywell, and ultimately will expedite the implementation of DMLS throughout various industrial sectors (automotive, biomedical, etc.).


Citation Formats

Watkins, Thomas R., Unocic, Kinga A., Maziasz, Philip J., Bunn, Jeffrey R., Fancher, Christopher M., Peralta, Alonso, Sundarraj, Suresh, and Neumann, James. Residual stress determination of direct metal laser sintered (DMLS) inconel specimens and parts. United States: N. p., 2018. Web. doi:10.2172/1415913.
Watkins, Thomas R., Unocic, Kinga A., Maziasz, Philip J., Bunn, Jeffrey R., Fancher, Christopher M., Peralta, Alonso, Sundarraj, Suresh, & Neumann, James. Residual stress determination of direct metal laser sintered (DMLS) inconel specimens and parts. United States. doi:10.2172/1415913.
Watkins, Thomas R., Unocic, Kinga A., Maziasz, Philip J., Bunn, Jeffrey R., Fancher, Christopher M., Peralta, Alonso, Sundarraj, Suresh, and Neumann, James. 2018. "Residual stress determination of direct metal laser sintered (DMLS) inconel specimens and parts". United States. doi:10.2172/1415913. https://www.osti.gov/servlets/purl/1415913.
@article{osti_1415913,
title = {Residual stress determination of direct metal laser sintered (DMLS) inconel specimens and parts},
author = {Watkins, Thomas R. and Unocic, Kinga A. and Maziasz, Philip J. and Bunn, Jeffrey R. and Fancher, Christopher M. and Peralta, Alonso and Sundarraj, Suresh and Neumann, James},
abstractNote = {Residual stress determinations and microstructural studies were performed on a series of Inconel 718Plus prisms built using Direct Metal Laser Sintering (DMLS) at Honeywell Aerospace (hereafter also referred to as Honeywell). The results are being used to validate and improve existing models at Honeywell, and ultimately will expedite the implementation of DMLS throughout various industrial sectors (automotive, biomedical, etc.).},
doi = {10.2172/1415913},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2018,
month = 1
}

Technical Report:

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  • Residual stress profiles were mapped using neutron diffraction in two simple prism builds of Inconel 718: one fabricated with electron beam melting and the other with direct laser sintering. Spatially indexed stress-free cubes were obtained by EDM sectioning equivalent prisms of similar shape. The (311) interplanar spacing examined for the EDM sectioned sample was compared to the interplanar spacings calculated to fulfill force and moment balance. We have shown that Applying force and moment balance is a necessary supplement to the measurements for the stress-free cubes with respect to accurate stress calculations in additively manufactured components. Furthermore, our work hasmore » shown that residual stresses in electron beam melting parts are much smaller than that of direct laser metal sintering parts.« less
  • In this paper, we investigate microstructure and quasi-static mechanical behavior of the direct metal laser sintered Inconel 718 superalloy as a function of build direction (BD). The printed material was further processed by annealing and double-aging, hot isostatic pressing (HIP), and machining. We characterize porosity fraction and distribution using micro X-ray computed tomography (μXCT), grain structure and crystallographic texture using electron backscattered diffraction (EBSD), and mechanical response in quasi-static tension and compression using standard mechanical testing at room temperature. Analysis of the μXCT imaging shows that majority of porosity develops in the outer layer of the printed material. However, porositymore » inside the material is also present. The EBSD measurements reveal formation of columnar grains, which favor < 001 > fiber texture components along the BD. These measurements also show evidence of coarse-grained microstructure present in the samples treated by HIP. Finally, analysis of grain boundaries reveal that HIP results in a large number of annealing twins compared to that in samples that underwent annealing and double-aging. The yield strength varies with the testing direction by approximately 7%, which is governed by a combination of grain morphology and crystallographic texture. In particular, we determine tension–compression asymmetry in the yield stress as well as anisotropy of the material flow during compression. We find that HIP lowers yield stress but improves ductility relative to the annealed and aged material. These results are discussed and critically compared with the data reported for wrought material in the same condition. - Highlights: • Microstructure and mechanical properties of DMLS Inconel 718 are studied in function of build direction. • Inhomogeneity of microstructure in the material in several conditions is quantified by μXCT and EBSD. • Anisotropy and asymmetry in the mechanical response are determined by tension and compression testing.« less