The influence of pulsed laser powder bed fusion process parameters on Inconel 718 material properties

Konstantinos Georgilas; Raja H.U. Khan; Mehmet E. Kartal

doi:10.1016/j.msea.2019.138527

The influence of pulsed laser powder bed fusion process parameters on Inconel 718 material properties

Konstantinos Georgilas^* (Corresponding Author), Raja H.U. Khan, Mehmet E. Kartal

^*Corresponding author for this work

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

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Abstract

In this work, the effect of pulsed laser used during the powder bed fusion (L-PBF) additive manufacturing (AM) process on Inconel 718 (IN718) material properties has been investigated. Argon gas atomised (AGA) IN718 powder is characterised in terms of flow, density, particle size distribution and morphology. Powder shows mostly spherical morphology with Hausner ratio of 1.17 indicating good flow characteristics. Density optimisation trials are carried out by varying laser power and exposure time. Fabricated samples are characterised in terms of porosity by area fraction analysis using light microscopy and volume fraction analysis using X-ray microcomputed tomography (micro-CT). Minimum porosity of 0.16% is achieved for laser power of 200 W and exposure time of 110 μs＀ Microstructural analysis using the Electron Backscatter Diffraction (EBSD) technique shows limited columnar grain structure in the Z direction and more equiaxed type grains in the XY direction (normal to the Z direction). Tensile test results show 754 MPa yield strength, 1070 MPa ultimate tensile strength and ~24% elongation. Finally, hole drilling residual stress measurements show increase from ~0 MPa to over 450 MPa in tensile stress up to a depth of 1 mm from the top surface of the as-build L-PBF IN718 sample. It has been found that laser pulsing produces higher homogeneity in grain structure and better mechanical properties than that by the continuous laser method.

Original language	English
Article number	138527
Number of pages	9
Journal	Materials Science and Engineering A
Volume	769
Early online date	9 Oct 2019
DOIs	https://doi.org/10.1016/j.msea.2019.138527
Publication status	Published - 2 Jan 2020

Bibliographical note

Funding
This publication was made possible by the sponsorship and support of Lloyd's Register Foundation, United Kingdom. The work was enabled through, and undertaken at, the National Structural Integrity Research Centre (NSIRC) United Kingdom, a postgraduate engineering facility for industry-led research into structural integrity established and managed by TWI through a network of both national and international Universities. Lloyd’s Register Foundation helps to protect life and property by supporting engineering-related education, public engagement and the application of research.

Data availability
The raw data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study. The processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study.

Keywords

Powder methods
Nickel alloys
Grains and interfaces
Stress/strain measurements
Characterisation
PARTS
HEAT-TREATMENT
MECHANICAL-PROPERTIES
ANISOTROPY
TEXTURE
RESIDUAL-STRESSES
SLM
TI-6AL-4V
MICROSTRUCTURE

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The_influence_of_Pulsed_LPBF_Process_Parameters_Georgilas_et_al_AAM
© 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
Accepted author manuscript, 1.14 MBLicence: CC BY-NC-ND

Cite this

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title = "The influence of pulsed laser powder bed fusion process parameters on Inconel 718 material properties",

abstract = "In this work, the effect of pulsed laser used during the powder bed fusion (L-PBF) additive manufacturing (AM) process on Inconel 718 (IN718) material properties has been investigated. Argon gas atomised (AGA) IN718 powder is characterised in terms of flow, density, particle size distribution and morphology. Powder shows mostly spherical morphology with Hausner ratio of 1.17 indicating good flow characteristics. Density optimisation trials are carried out by varying laser power and exposure time. Fabricated samples are characterised in terms of porosity by area fraction analysis using light microscopy and volume fraction analysis using X-ray microcomputed tomography (micro-CT). Minimum porosity of 0.16% is achieved for laser power of 200 W and exposure time of 110 μs＀ Microstructural analysis using the Electron Backscatter Diffraction (EBSD) technique shows limited columnar grain structure in the Z direction and more equiaxed type grains in the XY direction (normal to the Z direction). Tensile test results show 754 MPa yield strength, 1070 MPa ultimate tensile strength and ~24% elongation. Finally, hole drilling residual stress measurements show increase from ~0 MPa to over 450 MPa in tensile stress up to a depth of 1 mm from the top surface of the as-build L-PBF IN718 sample. It has been found that laser pulsing produces higher homogeneity in grain structure and better mechanical properties than that by the continuous laser method.",

keywords = "Powder methods, Nickel alloys, Grains and interfaces, Stress/strain measurements, Characterisation, PARTS, HEAT-TREATMENT, MECHANICAL-PROPERTIES, ANISOTROPY, TEXTURE, RESIDUAL-STRESSES, SLM, TI-6AL-4V, MICROSTRUCTURE",

author = "Konstantinos Georgilas and Khan, {Raja H.U.} and Kartal, {Mehmet E.}",

note = "Funding This publication was made possible by the sponsorship and support of Lloyd's Register Foundation, United Kingdom. The work was enabled through, and undertaken at, the National Structural Integrity Research Centre (NSIRC) United Kingdom, a postgraduate engineering facility for industry-led research into structural integrity established and managed by TWI through a network of both national and international Universities. Lloyd{\textquoteright}s Register Foundation helps to protect life and property by supporting engineering-related education, public engagement and the application of research. Data availability The raw data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study. The processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study.",

year = "2020",

month = jan,

day = "2",

doi = "10.1016/j.msea.2019.138527",

language = "English",

volume = "769",

journal = "Materials Science and Engineering A",

issn = "0921-5093",

publisher = "Elsevier BV",

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T1 - The influence of pulsed laser powder bed fusion process parameters on Inconel 718 material properties

AU - Georgilas, Konstantinos

AU - Khan, Raja H.U.

AU - Kartal, Mehmet E.

N1 - Funding This publication was made possible by the sponsorship and support of Lloyd's Register Foundation, United Kingdom. The work was enabled through, and undertaken at, the National Structural Integrity Research Centre (NSIRC) United Kingdom, a postgraduate engineering facility for industry-led research into structural integrity established and managed by TWI through a network of both national and international Universities. Lloyd’s Register Foundation helps to protect life and property by supporting engineering-related education, public engagement and the application of research. Data availability The raw data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study. The processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study.

PY - 2020/1/2

Y1 - 2020/1/2

N2 - In this work, the effect of pulsed laser used during the powder bed fusion (L-PBF) additive manufacturing (AM) process on Inconel 718 (IN718) material properties has been investigated. Argon gas atomised (AGA) IN718 powder is characterised in terms of flow, density, particle size distribution and morphology. Powder shows mostly spherical morphology with Hausner ratio of 1.17 indicating good flow characteristics. Density optimisation trials are carried out by varying laser power and exposure time. Fabricated samples are characterised in terms of porosity by area fraction analysis using light microscopy and volume fraction analysis using X-ray microcomputed tomography (micro-CT). Minimum porosity of 0.16% is achieved for laser power of 200 W and exposure time of 110 μs＀ Microstructural analysis using the Electron Backscatter Diffraction (EBSD) technique shows limited columnar grain structure in the Z direction and more equiaxed type grains in the XY direction (normal to the Z direction). Tensile test results show 754 MPa yield strength, 1070 MPa ultimate tensile strength and ~24% elongation. Finally, hole drilling residual stress measurements show increase from ~0 MPa to over 450 MPa in tensile stress up to a depth of 1 mm from the top surface of the as-build L-PBF IN718 sample. It has been found that laser pulsing produces higher homogeneity in grain structure and better mechanical properties than that by the continuous laser method.

AB - In this work, the effect of pulsed laser used during the powder bed fusion (L-PBF) additive manufacturing (AM) process on Inconel 718 (IN718) material properties has been investigated. Argon gas atomised (AGA) IN718 powder is characterised in terms of flow, density, particle size distribution and morphology. Powder shows mostly spherical morphology with Hausner ratio of 1.17 indicating good flow characteristics. Density optimisation trials are carried out by varying laser power and exposure time. Fabricated samples are characterised in terms of porosity by area fraction analysis using light microscopy and volume fraction analysis using X-ray microcomputed tomography (micro-CT). Minimum porosity of 0.16% is achieved for laser power of 200 W and exposure time of 110 μs＀ Microstructural analysis using the Electron Backscatter Diffraction (EBSD) technique shows limited columnar grain structure in the Z direction and more equiaxed type grains in the XY direction (normal to the Z direction). Tensile test results show 754 MPa yield strength, 1070 MPa ultimate tensile strength and ~24% elongation. Finally, hole drilling residual stress measurements show increase from ~0 MPa to over 450 MPa in tensile stress up to a depth of 1 mm from the top surface of the as-build L-PBF IN718 sample. It has been found that laser pulsing produces higher homogeneity in grain structure and better mechanical properties than that by the continuous laser method.

KW - Powder methods

KW - Nickel alloys

KW - Grains and interfaces

KW - Stress/strain measurements

KW - Characterisation

KW - PARTS

KW - HEAT-TREATMENT

KW - MECHANICAL-PROPERTIES

KW - ANISOTROPY

KW - TEXTURE

KW - RESIDUAL-STRESSES

KW - SLM

KW - TI-6AL-4V

KW - MICROSTRUCTURE

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U2 - 10.1016/j.msea.2019.138527

DO - 10.1016/j.msea.2019.138527

M3 - Article

SN - 0921-5093

VL - 769

JO - Materials Science and Engineering A

JF - Materials Science and Engineering A

M1 - 138527

ER -

The influence of pulsed laser powder bed fusion process parameters on Inconel 718 material properties

Abstract

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Mehmet Kartal

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The influence of pulsed laser powder bed fusion process parameters on Inconel 718 material properties

Abstract

Bibliographical note

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Mehmet Kartal

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