Abstract
The selection of heat source model is very important to accurately predict the distribution of temperature field and melting pool geometry in the numerical modeling of additive manufacturing process. The surface model, volumetric model and double-ellipsoid model are selected for comparison and analysis. These three heat source models are progarmmed as user-defined subroutines with Abaqus/Standard simulation software to predict the peak temperature and melting pool geometry during selective laser melting (SLM) of IN625. The comparison between simulation and experimental results shows that double-ellipsoid model can predict the melting pool geometry well, while the volumetric model provides comparative peak temperature predictions. In contrast, the surface model exhibits significant deviations in both melting pool geometry and peak temperature. The findings in this research highlight the need for model calibration or modification to enhance efficiency and accuracy before further research can be conducted.
Metal additive manufacturing (AM), as one of the emerging advanced manufacturing technologies, has demonstrated the great capability of manufacturing components with intricate geometry and free-form surfaces in comparison to conventional manufacturing processes, which has found successful application in various industries such as aerospace, automotive and medical device
In terms of additive manufacturing, selective laser melting (SLM) is one of the commonly utilized techniques for metal additive manufacturing including widely used nickel-based superalloys in the aerospace industry, which involves high-density energy, melting, liquidus material flowing, vaporization, and solidificatio
So far, several heat source models have been developed by many scholars to define heat transfer in the melting pool and powder bed, including Gaussian surface heat source, double-ellipsoidal heat source, and many other geometrically modified volumetric heat source
In this study, a three-dimensional finite element model for the fulfillment of SLM IN625 is built in Abaqus/Standard. The surface heat source model, volumetric model, and double-ellipsoid model are respectively presented and programmed as a user-defined subroutine implemented into Abaqus for modeling heat transfer in the IN625 powder bed. The predicted melting pool geometry and peak temperature are extracted validating against the experimental results cited from open literatures.
To model the laser heat distribution and transfer on the powder bed, the three most commonly used heat source models including the surface heat source model, volumetric heat source model, and double-ellipsoid heat source model have been selected for comparison in terms of efficiency and accuracy.
The frequently utilized surface heat flux equation with Gaussian distribution is listed as
(1) |
where q is the laser intensity, A the coefficient of laser absorption, P the nominal laser power, ω the laser spot radius, and (x0, y0) the coordinate of the laser spot center.
Based on the surface heat source model, the volumetric heat source model with Gaussian form takes into account the penetration of the laser beam into the powder bed, as shown in
(2) |

Fig.1 Schematic of heat source models
where η is the depth of laser beam penetration.
The double-ellipsoid heat source model was presented by Goldak et al
The front part of the double-ellipsoid can be written as
(3) |
While the rear part can be expressed as
(4) |
where af and ar denote the semi-axes of the front and rear ellipsoidal, respectively; and the ratios of controlling heat flux flows into the front and rear parts of the heat source, respectively; b and c the lengths of semi-axes along the y and z directions, respectively. The model constants associated with the above-mentioned equations are cited and listed in
Heat source model | Variable | Value | Source |
---|---|---|---|
Surface model | A | 0.3 |
Ref.[ |
Volumetric model | A | 0.3 |
Ref.[ |
η | 0.4 |
Ref.[ | |
Double⁃ellipsoid model | af/μm | 276 |
Refs.[ |
ar/μm | 1 520 | ||
b/μm | 160 | ||
c/μm | 160 | ||
ff | 1.4 | ||
fr | 0.6 |
In this research, the surface type, volumetric type, and double-ellipsoid type are selected to compare their efficiency and accuracy during the modeling of the SLM of IN625 nickel-based alloy. As shown in

Fig.2 3D FE model in SLM of IN625
Material property | Value |
---|---|
Density ρ/(kg· | 8 440 |
Liquidus temperature TL/℃ | 1 450 |
Solidus temperature TS/℃ | 1 290 |
Specific heat Cp/(J·k |
338.98 + 0.243 7T (T ≤ TS) 735 (T ≥ TL) |
Thermal conductivity k/(W· |
5.331 + 0.001 5 T (T ≤ TS) 30.05 (T ≥ TL) |
Latent heat of fusion/(J·k |
227 × 1 |
Thermal expansion coefficient βT/ |
1.28 × 1 |
The SLM processing parameters include the scanning speed of 100 mm/s and laser powder of 300, 400, and 500 W, respectively, which correspond to those used in Ref.[
During metal AM, the melting pool in which the solid particles change to liquid provides substantial information for a profound understanding of the AM proces

Fig.3 Characterization of melting pool geometry

Fig.4 Top view of molten pool geometry with different heat source models (P=500 W)

Fig.5 Cross-section view of molten pool geometry with different heat source models at different laser powers
As far as the melting pool geometry and peak temperature are concerned, some detailed information is listed in
Heat source model | Width /μm | Depth /μm | Peak temperature/℃ | ||||||
---|---|---|---|---|---|---|---|---|---|
300 W | 400 W | 500 W | 300 W | 400 W | 500 W | 300 W | 400 W | 500 W | |
Surface model | 482 | 500 | 550 | 72 | 82 | 100 | 6 383 | 8 486 | 10 730 |
Volumetric model | — | 176 | 230 | 12 | 87 | 166 | 1 339 | 1 596 | 1 875 |
Double⁃ellipsoid model | 324 | 372 | 500 | 225 | 246 | 287 | 4 837 | 6 270 | 7 760 |
Ref.[ | 307 | 385 | 455 | 179 | 274 | 321 | 1 916 | 2 172 | 2 388 |

Fig.6 Simulated temperature distribution along Z-direction at different laser powers

Fig.7 Simulated temperature distribution across the molten pool at different laser powers

Fig.8 Comparison of the transverse section of the melting pool at laser power of 500 W
Three commonly employed heat source models including surface, volumetric, and double-ellipsoid models are selected for accuracy and efficiency comparison in the SLM of IN625 nickel-based superalloys. A 3D FE model with implemented user-defined subroutines DFLUX is created in Abaqus/Standard for numerical modeling and analysis. The main conclusions are as follows:
(1) Concerning the melting pool geometry, the double-ellipsoid model provides acceptable results in comparison to the experimental result cited in the literature, while both the surface and volumetric models show large discrepancies.
(2) The simulated peak temperature with the volumetric model is relatively close to the reported value in the literature in comparison to surface and double-ellipsoid models, even though the absolute errors are all beyond 20% under various SLM processing parameters.
(3) Melting pool dimensions and peak temperature cannot be accurately captured simultaneously with either a double-ellipsoid or volumetric model. To guarantee the numerical model results during the SLM of IN625, the heat source model selection, calibration or modification is a basic prerequisite.
Contributions Statement
Dr. LI Binxun designed the study, conducted the analysis, interpreted the results and wrote the manuscript. Dr. SUN Yujing contributed to the discussion and background of the study. Prof. DU Jin contributed to the data analysis and funding acquisition. Dr. XIA Yan contributed to the finite element modeling. Prof. SU Guosheng contributed to the draft and language modifica⁃tion. Mr. ZHANG Qing contributed to the subroutine written. All authors commented on the manuscript draft and approved the submission.
Acknowledgements
This work was supported by the Natural Science Foundation of Shandong Province (No.ZR2021QE230), the Talent Research Project of Qilu University of Technology (Shandong Academy of Sciences) (No.2023RCKY118), and the National Natural Science Foundation of China (Nos.52275438, 52205480).
Conflict of Interest
The authors declare no competing interests.
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