On the evolution of microstructure and defect control in 316L SS components fabricated via directed energy deposition
To identify the critical issues that affect the evolution of microstructure during additive manufacturing, we investigated the influence of process parameters on the evolution of the dimensional and surface quality, microstructure, internal defects, and mechanical properties in 316L stainless steel...
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Published in | Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 764; no. C; p. 138243 |
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Main Authors | , , , , , , , |
Format | Journal Article |
Language | English |
Published |
Lausanne
Elsevier B.V
09.09.2019
Elsevier BV Elsevier |
Subjects | |
Online Access | Get full text |
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Summary: | To identify the critical issues that affect the evolution of microstructure during additive manufacturing, we investigated the influence of process parameters on the evolution of the dimensional and surface quality, microstructure, internal defects, and mechanical properties in 316L stainless steel (SS) components fabricated using laser engineered net shaping (LENS®), a directed energy deposition (DED) additive manufacturing (AM) technique. The results show that the accumulation of un-melted powder particles on the side walls of deposited sections can be avoided by selecting a laser under-focused condition. Moreover, we report that the variation of melt pool width is more sensitive to laser power than to the depth of the melt pool. The formation of a so-called “hierarchical” microstructure with cellular morphology is attributable to a combination of layer deposition and rapid solidification, which are characteristics of AM. Finally, we discuss microstructure evolution and defect formation, particularly the formation of multiple interfaces and the presence of un-melted powder particles and pores, in light of the dynamic convective fluid flow and rapid solidification that occur in the melt pool. X-ray computed tomography (X-CT) was used to precisely map the spatial distribution of pores in the DED components. The evolution of microstructure during DED is discussed in the context of related thermal phenomena in an effort to provide fundamental insight into the mechanisms that govern defect formation. |
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Bibliography: | AC04-94AL85000; NA0003525 SAND2019-9333J USDOE National Nuclear Security Administration (NNSA) |
ISSN: | 0921-5093 1873-4936 |
DOI: | 10.1016/j.msea.2019.138243 |