Laser powder bed fusion additive manufacturing of molybdenum using a nitrogen build atmosphere

Tejas Ramakrishnan; Eileen R.L. Espiritu; Sunyong Kwon; Mohsen K. Keshavarz; Jose A. Muniz-Lerma; Raynald Gauvin; Mathieu Brochu

doi:10.1016/j.ijrmhm.2024.106555

Laser powder bed fusion additive manufacturing of molybdenum using a nitrogen build atmosphere

Tejas Ramakrishnan, Eileen R.L. Espiritu, Sunyong Kwon, Mohsen K. Keshavarz, Jose A. Muniz-Lerma, Raynald Gauvin, Mathieu Brochu

Microstructural Evolution Modeling

Research output: Contribution to journal › Article › peer-review

8 Scopus citations

Abstract

A method was developed to suppress the crack formation during laser powder bed fusion (LPBF) of molybdenum (Mo). The method uses a nitrogen (N₂) atmosphere to fabricate crack-free samples without any additional processing. To compare with the effect of the N₂ atmosphere, samples were prepared under an argon (Ar) atmosphere as well with the same process parameters. The microstructure analyses by optical and high-resolution electron microscopy revealed that crack-free samples were produced under this condition, whereas grain boundary cracks were observed throughout the sample fabricated in Ar atmosphere. To understand the mechanism of crack prevention by nitrogen (N), the energetics of solute components in the BCC-Mo structure were studied by Density Functional Theory (DFT). The theoretical calculations showed that the introduction of N into the BCC-Mo hinders oxygen (O) diffusion, causing O entrapment in the lattice at interstitial positions. As a result, reduced oxides within grains and at grain boundaries (GB) were observed. The results are consistent with the experimental observation made from the fracture surface investigation. The reduced embrittlement of GB from the reduced GB oxide formation is believed to suppress GB cracking.

Original language	English
Article number	106555
Journal	International Journal of Refractory Metals and Hard Materials
Volume	119
DOIs	https://doi.org/10.1016/j.ijrmhm.2024.106555
State	Published - Feb 2024

Funding

The authors would like to thank the generous research support provided by the Natural Sciences and Engineering Research Council (NSERC) of Canada (NSERC Project Number: NETGP 494158–16). The authors would also like to acknowledge the McGill Engineering Doctoral Award (MEDA) granted to Tejas Ramakrishnan. We also thank Nicolas Brodusch in the Mining and Materials Engineering Department of McGill University for help in STEM operation and data collection, and Ashutosh Jena for help in jet polishing of TEM samples and TEM data collection. The authors would like to thank the generous research support provided by the Natural Sciences and Engineering Research Council (NSERC) of Canada (NSERC Project Number: NETGP 494158–16). The authors would also like to acknowledge the McGill Engineering Doctoral Award (MEDA) granted to Tejas Ramakrishnan. We also thank Nicolas Brodusch in the Mining and Materials Engineering Department of McGill University for help in STEM operation and data collection, and Ashutosh Jena for help in jet polishing of TEM samples and TEM data collection.

Keywords

Additive manufacturing
DFT calculations
Laser powder bed fusion
Molybdenum
Nitrogen

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10.1016/j.ijrmhm.2024.106555

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title = "Laser powder bed fusion additive manufacturing of molybdenum using a nitrogen build atmosphere",

abstract = "A method was developed to suppress the crack formation during laser powder bed fusion (LPBF) of molybdenum (Mo). The method uses a nitrogen (N2) atmosphere to fabricate crack-free samples without any additional processing. To compare with the effect of the N2 atmosphere, samples were prepared under an argon (Ar) atmosphere as well with the same process parameters. The microstructure analyses by optical and high-resolution electron microscopy revealed that crack-free samples were produced under this condition, whereas grain boundary cracks were observed throughout the sample fabricated in Ar atmosphere. To understand the mechanism of crack prevention by nitrogen (N), the energetics of solute components in the BCC-Mo structure were studied by Density Functional Theory (DFT). The theoretical calculations showed that the introduction of N into the BCC-Mo hinders oxygen (O) diffusion, causing O entrapment in the lattice at interstitial positions. As a result, reduced oxides within grains and at grain boundaries (GB) were observed. The results are consistent with the experimental observation made from the fracture surface investigation. The reduced embrittlement of GB from the reduced GB oxide formation is believed to suppress GB cracking.",

keywords = "Additive manufacturing, DFT calculations, Laser powder bed fusion, Molybdenum, Nitrogen",

author = "Tejas Ramakrishnan and Espiritu, {Eileen R.L.} and Sunyong Kwon and Keshavarz, {Mohsen K.} and Muniz-Lerma, {Jose A.} and Raynald Gauvin and Mathieu Brochu",

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AU - Ramakrishnan, Tejas

AU - Espiritu, Eileen R.L.

AU - Kwon, Sunyong

AU - Keshavarz, Mohsen K.

AU - Muniz-Lerma, Jose A.

AU - Gauvin, Raynald

AU - Brochu, Mathieu

PY - 2024/2

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N2 - A method was developed to suppress the crack formation during laser powder bed fusion (LPBF) of molybdenum (Mo). The method uses a nitrogen (N2) atmosphere to fabricate crack-free samples without any additional processing. To compare with the effect of the N2 atmosphere, samples were prepared under an argon (Ar) atmosphere as well with the same process parameters. The microstructure analyses by optical and high-resolution electron microscopy revealed that crack-free samples were produced under this condition, whereas grain boundary cracks were observed throughout the sample fabricated in Ar atmosphere. To understand the mechanism of crack prevention by nitrogen (N), the energetics of solute components in the BCC-Mo structure were studied by Density Functional Theory (DFT). The theoretical calculations showed that the introduction of N into the BCC-Mo hinders oxygen (O) diffusion, causing O entrapment in the lattice at interstitial positions. As a result, reduced oxides within grains and at grain boundaries (GB) were observed. The results are consistent with the experimental observation made from the fracture surface investigation. The reduced embrittlement of GB from the reduced GB oxide formation is believed to suppress GB cracking.

AB - A method was developed to suppress the crack formation during laser powder bed fusion (LPBF) of molybdenum (Mo). The method uses a nitrogen (N2) atmosphere to fabricate crack-free samples without any additional processing. To compare with the effect of the N2 atmosphere, samples were prepared under an argon (Ar) atmosphere as well with the same process parameters. The microstructure analyses by optical and high-resolution electron microscopy revealed that crack-free samples were produced under this condition, whereas grain boundary cracks were observed throughout the sample fabricated in Ar atmosphere. To understand the mechanism of crack prevention by nitrogen (N), the energetics of solute components in the BCC-Mo structure were studied by Density Functional Theory (DFT). The theoretical calculations showed that the introduction of N into the BCC-Mo hinders oxygen (O) diffusion, causing O entrapment in the lattice at interstitial positions. As a result, reduced oxides within grains and at grain boundaries (GB) were observed. The results are consistent with the experimental observation made from the fracture surface investigation. The reduced embrittlement of GB from the reduced GB oxide formation is believed to suppress GB cracking.

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KW - DFT calculations

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Laser powder bed fusion additive manufacturing of molybdenum using a nitrogen build atmosphere

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