Effect of Scanning Strategy on Thermal Stresses and Strains during Electron Beam Melting of Inconel 625: Experiment and Simulation
Abstract
:1. Introduction
2. Experiments and Methods
2.1. EBM Processing
2.2. Measurement and Testing
2.3. Simulation and Modeling
2.3.1. Simulation Assumptions
2.3.2. Simulation Settings
3. Results
3.1. High-Temperature Tensile Properties
3.2. Truss Size and Defect Analysis
3.3. Deflection and Thermal Stress Analysis Truss Size and Defect Analysis
3.3.1. Long Scanning Parts
3.3.2. Short-Y Scanning Parts
3.3.3. Chessboard Scanning
4. Discussion
4.1. Thermal Stresses and Developed Strains during EBM
4.2. Relation of Scanning Strategy to Part Quality in EBM
5. Conclusions
- The thermal stresses on the trusses from different scanning strategies reach the UTS of IN625 (58 MPa) during EBM (1050 °C in this work). However, this does not mean that the part necessarily fails. In fact, failure is rather strain-controlled since it only occurs when the plastic strain increases to a certain level (around 0.33 in this work, according to both experiments and simulations);
- The scanning length was the main parameter to control the induced thermal plastic strain. Shorter scanning lines were always favored since they prevented the accumulation of strains in long lengths. In addition, shorter scans had a slightly positive influence on density due to increasing the local temperature. However, it is noted that the short-Y scanning strategy led to an unsymmetrical bending between the two sides of the deflection sample which has not been reported as an issue for the SLM process. This was attributed to the change in heat transfer and hence shrinkage direction during EBM;
- The rotation angle in each layer was another important parameter that determined the scanning length. Accordingly, since a proper rotation angle decreased the scanning length in successive layers, a layer rotation was recommended to reduce the thermal deformation;
- Interestingly, unlike the SLM process, the differences in thermal stresses/strains between bidirectional and unidirectional patterns were rather small and even negligible in some cases.
- The chessboard scanning can effectively mitigate the bending and prevent the rupture of the trusses. This was due to the short scanning lengths of the islands. However, large cracks could form at the overlapping scanning regions due to the opposite pulling of the adjacent islands;
- In summary, to minimize part failure in EBM due to thermal deformations, it is suggested to use a bidirectional scanning pattern while rotating/orienting the scanning direction in such a manner that one can deliver the part using shorter scans. This can be a lesson for machine software developers;
- Moreover, as recognized from this work, the processing temperature for IN625 using EBM should be lower. A proper processing temperature should be below the embrittlement temperature for such an alloy.
Supplementary Materials
Author Contributions
Funding
Data Availability Statement
Conflicts of Interest
References
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Scanning | Sample ID | NO. of Islands | Starting Angle | Rotation Angle per Layer (°) |
---|---|---|---|---|
Long | S0R0 | 1 | 0 | 0 |
S0R72 | 1 | 0 | ~72 (Default setting) | |
S0R90 | 1 | 0 | 90 | |
S0R180 | 1 | 0 | 180 | |
Short-Y | S90R0 | 1 | 90 | 0 |
S90R180 | 1 | 90 | 180 | |
Short Chessboard | 10I:S0/90R0 | 10 | 0/90 | 0 |
Scanning | Sample ID | Layer Number | Scanning Angle (°) | Average Scanning Length (mm) | Layer Scanning Duration (s) | |
---|---|---|---|---|---|---|
Bidirectional | Unidirectional | |||||
Long | S0R0 | every | 0 | 100 | 1.99 ± 0.28 | 2.07 ± 0.34 |
S0R72 | n | 0 | 100 | 1.99 ± 0.28 | 2.07 ± 0.34 | |
n + 1 | 72 | 10.51 | 13.84 ± 2.50 | 15.46 ± 2.97 | ||
n + 2 | 144 | 17.01 | 4.40 ± 0.16 | 4.79 ± 0.20 | ||
n + 3 | 216 | 17.01 | 6.18 ± 1.51 | 6.67 ± 1.61 | ||
n + 4 | 288 | 10.51 | 13.10 ± 1.38 | 14.22 ± 1.74 | ||
S0R90 | n | 0 | 100 | 1.99 ± 0.28 | 2.07 ± 0.34 | |
n + 1 | 90 | 10 | 14.20 ± 1.89 | 15.76 ± 2.25 | ||
n + 2 | 180 | 100 | 1.72 ± 0.27 | 2.13 ± 0.20 | ||
n + 3 | 270 | 10 | 14.19 ± 1.83 | 15.66 ± 2.15 | ||
S0R180 | n | 0 | 100 | 1.99 ± 0.28 | 2.07 ± 0.34 | |
n + 1 | 180 | 100 | 1.72 ± 0.27 | 2.13 ± 0.20 | ||
Short-Y | S90R0 | every | 90 | 10 | 14.20 ± 1.89 | 15.76 ± 2.25 |
S90R180 | n | 90 | 10 | 14.20 ± 1.89 | 15.76 ± 2.25 | |
n + 1 | 270 | 10 | 14.19 ± 1.83 | 15.66 ± 2.15 | ||
Short chessboard | 10I: S0/90R0 * | every | 0 | 10 | 7.70 ± 1.02 | 8.35 ± 1.17 |
90 | 10 | 7.88 ± 1.08 | 8.90 ± 1.27 |
Density (g/cm3) | Young’s Modulus (GPa) * | Poisson’s Ratio | Yield Stress and Plastic Strain * | |
---|---|---|---|---|
Stress (MPa) | Plastic Strain | |||
8.44 | 45 | 0.33 | 46 | 0 |
55.4 | 0.00035 | |||
58 | 0.0015 |
Scanning | Sample ID | Bidirectional | Unidirectional | ||||
---|---|---|---|---|---|---|---|
Width (mm) | Thickness (mm) | Height (mm) | Width (mm) | Thickness (mm) | Height (mm) | ||
Long | S0R0 | 1.7 ± 0.14 | 1.0 ± 0.10 | 3.7 ± 0.04 | 1.5 ± 0.09 | 1.0 ± 0.08 | 3.7 ± 0.09 |
S0R72 | 1.3 ± 0.03 | 1.1 ± 0.06 | 3.8 ± 0.06 | 1.5 ± 0.05 | 1.3 ± 0.05 | 3.8 ± 0.03 | |
S0R90 | 1.6 ± 0.04 | 1.2 ± 0.04 | 3.7 ± 0.12 | 1.7 ± 0.09 | 1.3 ± 0.10 | 3.7 ± 0.05 | |
S0R180 | 1.8 ± 0.07 | 1.1 ± 0.01 | 3.6 ± 0.01 | 2.0 ± 0.07 | 1.2 ± 0.03 | 3.8 ± 0.05 | |
Short-Y | S90R0 | 1.2 ± 0.02 | 1.2 ± 0.04 | 3.8 ± 0.06 | 1.3 ± 0.10 | 1.3 ± 0.03 | 3.7 ± 0.06 |
S90R180 | 1.2 ± 0.04 | 1.2 ± 0.04 | 3.8 ± 0.07 | 1.3 ± 0.04 | 1.3 ± 0.03 | 3.8 ± 0.06 | |
Short chessboard | 10I: S0/90R0 | 1.6 ± 0.08 | 1.5 ± 0.07 | 3.6 ± 0.05 | 1.7 ± 0.07 | 1.7 ± 0.03 | 3.7 ± 0.08 |
CAD model | Designed | 1 | 1 | 5 | 1 | 1 | 5 |
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Zhao, X.; Wei, Y.; Mansour, R.; Dadbakhsh, S.; Rashid, A. Effect of Scanning Strategy on Thermal Stresses and Strains during Electron Beam Melting of Inconel 625: Experiment and Simulation. Materials 2023, 16, 443. https://doi.org/10.3390/ma16010443
Zhao X, Wei Y, Mansour R, Dadbakhsh S, Rashid A. Effect of Scanning Strategy on Thermal Stresses and Strains during Electron Beam Melting of Inconel 625: Experiment and Simulation. Materials. 2023; 16(1):443. https://doi.org/10.3390/ma16010443
Chicago/Turabian StyleZhao, Xiaoyu, Yuan Wei, Rami Mansour, Sasan Dadbakhsh, and Amir Rashid. 2023. "Effect of Scanning Strategy on Thermal Stresses and Strains during Electron Beam Melting of Inconel 625: Experiment and Simulation" Materials 16, no. 1: 443. https://doi.org/10.3390/ma16010443