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Proceedings Paper

Microstructural evolution and mechanical behavior of nickel-based superalloy 625 made by selective laser melting
Author(s): David B. Witkin; Paul Adams; Thomas Albright
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Paper Abstract

The mechanical properties and microstructures of Selective Laser Melted (SLM) alloy 625 procured from different suppliers were compared. The post-SLM process of hot isostatic pressing (HIP) led to a relatively coarse recrystallized gamma matrix phase that was similar in all the suppliers’ materials, resulting in nearly identical tensile properties. These similarities obscure significant differences between them with respect to the population of second phase particles, which consisted of carbides or Laves phase. During solidification, the final liquid phase is concentrated in Nb, Mo, Si and C, and leads to L → γ + carbide/Laves eutectic reactions. Secondary particles are very small prior to HIP and their composition has not been analyzed yet, but are limited to the fine-grained eutectic regions of the material prior to HIP. During HIP the gamma phase recrystallizes to remove the original as-solidified SLM microstructure, but secondary particles nucleate and grow where their elemental constituents first solidified, leading to a non-homogeneous distribution. Quasi-static tensile properties do not appear to be sensitive to these differences, but it is likely that other mechanical properties will be affected, especially fatigue and fracture behavior. Surface roughness, large grain size, and pores and voids left unhealed by the HIP cycle will also influence fatigue and fracture. Surface roughness and porosity in particular are features that could be improved by implementing novel approaches to laser processing in SLM.

Paper Details

Date Published: 16 March 2015
PDF: 12 pages
Proc. SPIE 9353, Laser 3D Manufacturing II, 93530B (16 March 2015); doi: 10.1117/12.2083699
Show Author Affiliations
David B. Witkin, The Aerospace Corp. (United States)
Paul Adams, The Aerospace Corp. (United States)
Thomas Albright, The Aerospace Corp. (United States)


Published in SPIE Proceedings Vol. 9353:
Laser 3D Manufacturing II
Henry Helvajian; Alberto Piqué; Martin Wegener; Bo Gu, Editor(s)

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