Track-Scale Simulations of Selective Laser Melting to Investigate Development and Mitigation of Thermal Stresses

Sharma, Rahul; Kumar, Arvind

doi:10.1007/s40516-019-00103-0

Cited by 11 publications

(4 citation statements)

References 26 publications

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“…Residual stress induced by laser powder bed fusion (PBF-LB) can surpass the yield strength of the metal [6]. Such high residual stress buildup could affect the microstructure and mechanical properties of the fabricated part [7]. There are thermal and mechanical treatments available to reduce residual stress.…”

Section: Introductionmentioning

confidence: 99%

Mechanics Modeling of Residual Stress Considering Effect of Preheating in Laser Powder Bed Fusion

Mirkoohi

Tran

et al. 2021

JMMP

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This study aimed at the investigation of the effect of substrate temperature on residual stress in laser powder bed fusion using a physics-based analytical model. In this study, an analytical model is proposed to predict the residual stress through the calculation of preheating affected temperature profile and thermal stress. The effect of preheating is super-positioned with initial temperature in the modeling of temperature profile using a moving heat source approach; the resultant temperature gradient is then employed to predict the thermal stress from a point body load approach. If the thermal stress exceeds the yield strength of the material, then the residual stress under cyclic heating and cooling will be calculated based on the incremental plasticity and kinematic hardening behavior of metal. IN718 is used as a material example to pursue this investigation. To validate the predicted residual stress, experimental measurements are conducted using X-ray diffraction on IN718 samples manufactured via laser powder bed fusion under different process conditions. Results showed that preheating of the substrate could reduce the residual stress in an additively manufactured part due to the reduction in temperature gradient and resultant shrinkage stresses. However, the excessive preheating could have an opposite impact on residual stress accumulation. Moreover, the results confirm that the proposed model is a valuable tool for the prediction of residual stress, eliminating the costly experiments and time-consuming finite element simulations.

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Section: Introductionmentioning

confidence: 99%

Mechanics Modeling of Residual Stress Considering Effect of Preheating in Laser Powder Bed Fusion

Mirkoohi

Tran

et al. 2021

JMMP

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“…In this strategy, after completing the previous scanning vector, the next scanning vector was initiated in the higher-temperature region. This led to decreasing the temperature gradient and reducing the residual stress [41]. However, as the scanning process proceeded towards the central region, the laser single-scan path became longer, leading to an increase in the temperature gradient and a gradual increase in the residual stress [42].…”

Section: Distribution and Types Of Cracksmentioning

confidence: 99%

Influence of Scanning Strategy and Post-Treatment on Cracks and Mechanical Properties of Selective-Laser-Melted K438 Superalloy

Zhang,

Yan,

Xia

et al. 2024

Coatings

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The feasibility of manufacturing high-performance components with complex structures is limited due to cracks in some superalloys fabricated by selective laser melting (SLM). By controlling the main process parameters such as scanning strategy, the adverse effects of cracks can be effectively reduced. In this paper, the effects of two different SLM scanning strategies with island and ‘back-and-forth’ and post-heat treatment on the cracks and mechanical properties of selective-laser-melted (SLMed) K438 alloy were investigated. The results show that the SLM method of the ‘back-and-forth’ scanning strategy had better lap and interlayer rotation angles and a more uniform distribution of laser energy compared with the island scanning strategy. The residual stress accumulation was reduced and crack formation was inhibited under this scanning strategy owing to the cooling and shrinkage process. In addition, the dislocation motion was hindered by the formation of uniformly dispersed MC carbides and γ’ phases during the SLM K438 alloy process, which resulted in the density of the as-built SLMed K438 alloy being up to 99.34%, the hardness up to 9.6 Gpa, and the tensile strength up to 1309 MPa. After post-heat treatment, the fine secondary γ’ phases were precipitated and dispersed uniformly in the Ni matrix, which effectively improved the Young’s modulus and tensile strength of the alloy by dispersing the stress-concentrated area.

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“…Zou et al [28] found that if the number of laser beams was raised from one to four, the residual stresses would be substantially greater, resulting in an increase in the intake of heat. Compared with no preheating, Sharma et al [29] found that preheating the substrate to 673 K decreased the residual stresses by 41% at the highest value. According to the above-mentioned research, laser power, layer thickness, and scanning speed are known to affect the residual stress, but no definitive conclusions can be drawn about the relationship between these key process parameters and the residual stress generated during the SLM or DED process.…”

Section: Introductionmentioning

confidence: 99%

A Study on the Thermo-Mechanical History, Residual Stress, and Dynamic Recrystallization Mechanisms in Additively Manufactured Austenitic Stainless Steels

Zhou

Zou

et al. 2022

Metals

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In this work, both numerical simulations and experimental characterization were used to obtain a broad understanding of the thermo-mechanical history, residual stress, and microstructure of the directed energy deposition (DED) process of austenitic stainless steels. To investigate the effect of process factors on residual stress, the global sensitivity analysis approach based on D-MORPH-HDMR was utilized. The results of the research reveal that the amplified effect of the influence of the three input variables (layer thickness, L; laser power, P; and scanning speed, v) on the transverse residual stress and thickness-direction residual stress is L > P > v; in contrast, the influence of longitudinal residual stress is P > L > v. We also found that general tendencies in local plastic strain accumulation are analogous to the relative distribution of geometrically necessary dislocations (GNDs). Additionally, we investigated post-solidification structures connected to residual stress, such as submicron dislocation cells and dynamic recrystallization (DRX) in austenitic stainless steels during DED. The investigation revealed that the DDRX and CDRX phenomena were caused by the bulging of initial grain boundaries and progressive sub-grain rotation (PSR). The fact that the sample bottom had more thermo-mechanical cycles than the top led to a higher dislocation density and hence more DDRX. This study presents a unique perspective on the link between residual stress and microstructure in additive manufacturing.

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Track-Scale Simulations of Selective Laser Melting to Investigate Development and Mitigation of Thermal Stresses

Cited by 11 publications

References 26 publications

Mechanics Modeling of Residual Stress Considering Effect of Preheating in Laser Powder Bed Fusion

Mechanics Modeling of Residual Stress Considering Effect of Preheating in Laser Powder Bed Fusion

Influence of Scanning Strategy and Post-Treatment on Cracks and Mechanical Properties of Selective-Laser-Melted K438 Superalloy

A Study on the Thermo-Mechanical History, Residual Stress, and Dynamic Recrystallization Mechanisms in Additively Manufactured Austenitic Stainless Steels

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