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Metal additive manufacturing has become integral to the modern aerospace and defense industry. Technologies such as powder bed fusion and direct energy deposition have reshaped these sectors. However, challenges like anisotropy and process-related defects still prevent the direct use of printed parts without post-processing. Electron beam powder bed fusion (EB-PBF) is well known for allowing builds at elevated temperatures and eliminating the need for stress relief. However, EB-PBF parts also experience epitaxial growth in the build direction, which causes anisotropy. This research explores two scanning strategies with spot melting techniques— stochastic and single directional—to fabricate IN718 parts using EB-PBF. After fabrication, the samples were analyzed using EBSD to evaluate grain formation in all directions. The findings suggest that point-based melting, guided by these strategies, can affect the microstructure in the build direction. This advancement offers the potential for tailoring controlled parts in future applications.
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This content will become publicly available on December 1, 2025
Microstructure Refinement of Bulk Inconel 718 Parts During Fabrication with EB-PBF Using Scanning Strategies: Transition from Bidirectional-Raster to Stochastic Point-Based Melting
Inconel 718 is a widely popular aerospace superalloy known for its high-temperature performance and resistance to oxidation, creep, and corrosion. Traditional manufacturing methods, like casting and powder metallurgy, face challenges with intricate shapes that can result in porosity and uniformity issues. On the other hand, Additive Manufacturing (AM) techniques such as Powder Bed Fusion (PBF) and Direct Energy Deposition (DED) can allow the creation of intricate single-part components to reduce weight and maintain structural integrity. However, AM parts often exhibit directional solidification, leading to anisotropic properties and potential crack propagation sites. To address this, post-processing treatments like HIP and heat treatment are necessary. This study explores the effects of the raster and stochastic spot melt scanning strategies on the microstructural and mechanical properties of IN718 parts fabricated using Electron Beam Powder Bed Fusion (EB-PBF). This research demonstrates that raster scanning produces columnar grains with higher mean aspect ratios. Stochastic spot melt scanning facilitates the formation of equiaxed grains, which enhances microstructural refinement and lowers anisotropy. The highest microstructural values were recorded in the raster-produced columnar grain structure. Conversely, the stochastic melt-produced transition from columnar to equiaxed grain structure demonstrated increased hardness with decreasing grain size; however, the hardness of the smallest equiaxed grain structure was slightly less than that of the columnar grain structure. These findings underscore the vital importance of scanning strategies in optimizing the EB-PBF process to enhance material properties.
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- Award ID(s):
- 2117801
- PAR ID:
- 10635048
- Publisher / Repository:
- MDPI
- Date Published:
- Journal Name:
- Journal of Manufacturing and Materials Processing
- Volume:
- 8
- Issue:
- 6
- ISSN:
- 2504-4494
- Page Range / eLocation ID:
- 241
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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