Abstract
Laser-based additive manufacturing of metals relies on many micro-sized welds to build a part. A simplified, well-studied case of this process is a single scan of the laser across a single layer of powder. However, there is a lack of mechanical property measurements of the tracks produced in such experiments. Nanoindentation measurements on laser track cross sections of nickel superalloy 625 reveal hardness differences between the track melt pool and base material as well as variations with laser scan speed. There is a change from ≈5.5 GPa in the track melt pool to ≈4.8 GPa in the base material for laser settings of 195 W and 800 mm s−1. In comparison, the increase in hardness in the melt pool is not observed for settings of 195 W and 200 mm s−1. It is believed that the difference in thermal histories supported by thermographic measurements causes a difference in the dislocation density in the melt pool . This results in a difference in hardness between the two tracks. The effects of the local crystal orientation, dendritic spacing, and residual stress are considered in the interpretation of results.
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Certain commercial equipment, instruments, or materials are identified in this paper in order to specify the experimental procedure adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the materials or equipment identified are necessarily the best available for the purpose.
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Acknowledgements
We wish to thank Will Osborn and Maureen Williams of the Materials Measurement Laboratory at NIST for their help with EBSD. We are very appreciative of Mark Stoudt of the Materials Measurement Laboratory at NIST for etching samples and discussing the many aspects of additive nickel superalloy 625. We are also grateful of Lyle Levine and Will Osborn of the Materials Measurement Laboratory at NIST for bringing to our attention the need to do these experiments. Meir Kreitman wishes to acknowledge support from the University of Maryland and the NIST Summer Undergraduate Research Fellowship (SURF) program.
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© 2019 The Minerals, Metals & Materials Society
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Weaver, J.S., Kreitman, M., Heigel, J.C., Donmez, M.A. (2019). Mechanical Property Characterization of Single Scan Laser Tracks of Nickel Superalloy 625 by Nanoindentation. In: TMS 2019 148th Annual Meeting & Exhibition Supplemental Proceedings. The Minerals, Metals & Materials Series. Springer, Cham. https://doi.org/10.1007/978-3-030-05861-6_24
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DOI: https://doi.org/10.1007/978-3-030-05861-6_24
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