Resilience of laser powder bed fusion additive manufacturing to programmatically induced laser power anomalies

Christine Cummings; David J. Corbin; Edward W. Reutzel; Abdalla R. Nassar

doi:10.2351/7.0001001

Resilience of laser powder bed fusion additive manufacturing to programmatically induced laser power anomalies

Christine Cummings, David J. Corbin, Edward W. Reutzel, Abdalla R. Nassar

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

3 Scopus citations

Abstract

Spatter interactions, varying power or scanner parameters, and uneven powder spreading in laser powder bed fusion (LPBF) can trigger the formation of lack-of-fusion or keyhole pores. In this paper, a strategy to mimic natural process anomalies is developed by varying the programmed laser power in a predefined region over sequential layers in order to understand the physics of pore formation and enable the systematic study of the sensitivity of LPBF processed Ti-6Al-4V to process anomalies. Results indicate that lack-of-fusion pores, caused by a decreased laser power input, and located at a depth equal to or less than the subsequent melt pool depth, are partially or fully healed by subsequent, nominally processed layers. Under conditions tested here, lack-of-fusion pores as deep as two layers (∼120 μm) below the surface are healed on subsequent layers. Conversely, local increases in laser power cause persistent keyhole pores, owing to the depth at which keyhole pores become entrapped into the melt—in this work, up to eight layers or 420 μm deep. These results show that while keyhole-induced porosity remains unaffected by the processing of subsequent layers, LPBF is resilient to a set of process anomalies, which would result in lack-of-fusion if not for subsequent remelting on layers above.

Original language	English
Article number	032005
Journal	Journal of Laser Applications
Volume	35
Issue number	3
DOIs	https://doi.org/10.2351/7.0001001
State	Published - Aug 1 2023
Externally published	Yes

Funding

The authors would like to acknowledge Ryan Overdorff and Jared Blecher of 3D Systems, Inc. for assisting with the generation of the build plan and operating the LPBF machine, Anil Chaudhary from Applied Optimization for numerous discussions related to the methodology and findings, Peter Le from Northrup Grumman for coordinating the x-ray computed tomography scans, and Jason Scherer from PSU ARL for programming the power regulation controller. This effort was performed through the National Center for Defense Manufacturing and Machining under the America Makes Program entitled “Generation and Characterization of Parameter- and Process-induced Defects” and is based on research sponsored by Air Force Research Laboratory under Agreement No. FA8650-16-2-5700. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation thereon. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the Government. Distribution authorized to U.S. Government Agencies and America Makes Members. Other request for this document shall be referred to AFRL/RXMS, Wright-Patterson Air Force Base, OH 45433-7750. The authors would like to acknowledge Ryan Overdorff and Jared Blecher of 3D Systems, Inc. for assisting with the generation of the build plan and operating the LPBF machine, Anil Chaudhary from Applied Optimization for numerous discussions related to the methodology and findings, Peter Le from Northrup Grumman for coordinating the x-ray computed tomography scans, and Jason Scherer from PSU ARL for programming the power regulation controller. This effort was performed through the National Center for Defense Manufacturing and Machining under the America Makes Program entitled “Generation and Characterization of Parameter- and Process-induced Defects” and is based on research sponsored by Air Force Research Laboratory under Agreement No. FA8650-16-2-5700. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation thereon. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the Government. Distribution authorized to U.S. Government Agencies and America Makes Members. Other request for this document shall be referred to AFRL/RXMS, Wright-Patterson Air Force Base, OH 45433-7750.

Funders	Funder number
LPBF
National Center for Defense Manufacturing and Machining
PSU ARL
Wright-Patterson Air Force Base	OH 45433-7750
Air Force Research Laboratory	FA8650-16-2-5700

Keywords

keyhole
lack-of-fusion
porosity
Ti-6Al-4V
x-ray computed tomography

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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10.2351/7.0001001

Cite this

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title = "Resilience of laser powder bed fusion additive manufacturing to programmatically induced laser power anomalies",

abstract = "Spatter interactions, varying power or scanner parameters, and uneven powder spreading in laser powder bed fusion (LPBF) can trigger the formation of lack-of-fusion or keyhole pores. In this paper, a strategy to mimic natural process anomalies is developed by varying the programmed laser power in a predefined region over sequential layers in order to understand the physics of pore formation and enable the systematic study of the sensitivity of LPBF processed Ti-6Al-4V to process anomalies. Results indicate that lack-of-fusion pores, caused by a decreased laser power input, and located at a depth equal to or less than the subsequent melt pool depth, are partially or fully healed by subsequent, nominally processed layers. Under conditions tested here, lack-of-fusion pores as deep as two layers (∼120 μm) below the surface are healed on subsequent layers. Conversely, local increases in laser power cause persistent keyhole pores, owing to the depth at which keyhole pores become entrapped into the melt—in this work, up to eight layers or 420 μm deep. These results show that while keyhole-induced porosity remains unaffected by the processing of subsequent layers, LPBF is resilient to a set of process anomalies, which would result in lack-of-fusion if not for subsequent remelting on layers above.",

keywords = "keyhole, lack-of-fusion, porosity, Ti-6Al-4V, x-ray computed tomography",

author = "Christine Cummings and Corbin, {David J.} and Reutzel, {Edward W.} and Nassar, {Abdalla R.}",

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AU - Corbin, David J.

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AU - Nassar, Abdalla R.

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N2 - Spatter interactions, varying power or scanner parameters, and uneven powder spreading in laser powder bed fusion (LPBF) can trigger the formation of lack-of-fusion or keyhole pores. In this paper, a strategy to mimic natural process anomalies is developed by varying the programmed laser power in a predefined region over sequential layers in order to understand the physics of pore formation and enable the systematic study of the sensitivity of LPBF processed Ti-6Al-4V to process anomalies. Results indicate that lack-of-fusion pores, caused by a decreased laser power input, and located at a depth equal to or less than the subsequent melt pool depth, are partially or fully healed by subsequent, nominally processed layers. Under conditions tested here, lack-of-fusion pores as deep as two layers (∼120 μm) below the surface are healed on subsequent layers. Conversely, local increases in laser power cause persistent keyhole pores, owing to the depth at which keyhole pores become entrapped into the melt—in this work, up to eight layers or 420 μm deep. These results show that while keyhole-induced porosity remains unaffected by the processing of subsequent layers, LPBF is resilient to a set of process anomalies, which would result in lack-of-fusion if not for subsequent remelting on layers above.

AB - Spatter interactions, varying power or scanner parameters, and uneven powder spreading in laser powder bed fusion (LPBF) can trigger the formation of lack-of-fusion or keyhole pores. In this paper, a strategy to mimic natural process anomalies is developed by varying the programmed laser power in a predefined region over sequential layers in order to understand the physics of pore formation and enable the systematic study of the sensitivity of LPBF processed Ti-6Al-4V to process anomalies. Results indicate that lack-of-fusion pores, caused by a decreased laser power input, and located at a depth equal to or less than the subsequent melt pool depth, are partially or fully healed by subsequent, nominally processed layers. Under conditions tested here, lack-of-fusion pores as deep as two layers (∼120 μm) below the surface are healed on subsequent layers. Conversely, local increases in laser power cause persistent keyhole pores, owing to the depth at which keyhole pores become entrapped into the melt—in this work, up to eight layers or 420 μm deep. These results show that while keyhole-induced porosity remains unaffected by the processing of subsequent layers, LPBF is resilient to a set of process anomalies, which would result in lack-of-fusion if not for subsequent remelting on layers above.

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Resilience of laser powder bed fusion additive manufacturing to programmatically induced laser power anomalies

Abstract

Funding

Keywords

UN SDGs

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