scholarly journals Numerical Investigation of Thermo-Mechanical Field during Selective Laser Melting Process with Experimental Validation

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1003
Author(s):  
Lan Li ◽  
Frank Liou
Keyword(s):  
Stainless Steel ◽  
Selective Laser Melting ◽  
Thermal Stresses ◽  
Pool Size ◽  
Solidification Structure ◽  
Temperature History ◽  
304L Stainless Steel ◽  
Laser Melting ◽  
Melt Pool ◽  
Melt Pool Size

In this study, thermo-mechanical simulation was conducted to predict thermal and stress behavior in Selective Laser Melting (SLM). Temperature-dependent material properties for processed material 304L stainless steel were incorporated into the model in order to capture the change from powder to fully dense solid stainless steel. Temperature and thermal stress history were tracked under conditions of different parameter sets which were designed to reduce defect formation. The thermal model predicted the temperature history for multi-track scans under different process parameters, such as laser power, effective scanning speed and hatch spacing. Subsequently, the corresponding melt-pool size, solidification rate and temperature gradients could be calculated from simulated temperature data. These three parameters from the simulation were compared with experimental melt pool size, grain structure and cell spacing data obtained from a Renishaw AM250. The experimental data were also used to determine unknown simulation parameters required by the continuum model, e.g., the optical penetration depth and thermal conductivity multiplier for the molten region. This allowed the simulation model to accurately predict melt pool size and solidification structure of SLM 304L stainless steel. Simulated stress showed that the subsequent thermal cyclic melting in successive scanned tracks resulted in alternating compressive and tensile thermal stresses. This work will provide insight for studying microstructure morphology, residual stress and deformations in the SLM process of 304L stainless steel.

Estimation of melt pool size by complementary use of external illumination and process emission in coaxial monitoring of selective laser melting

2019 ◽  
Vol 31 (2) ◽  
pp. 022305 ◽  
Author(s):  
Matteo Pacher ◽  
Luca Mazzoleni ◽  
Leonardo Caprio ◽  
Ali Gökhan Demir ◽  
Barbara Previtali
Keyword(s):  
Selective Laser Melting ◽  
Pool Size ◽  
Laser Melting ◽  
Melt Pool ◽  
Melt Pool Size

scholarly journals Effect of Hatch Spacing on Melt Pool and As-built Quality During Selective Laser Melting of Stainless Steel: Modeling and Experimental Approaches

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 50 ◽  
Author(s):  
Zhichao Dong ◽  
Yabo Liu ◽  
Weibin Wen ◽  
Jingran Ge ◽  
Jun Liang
Keyword(s):  
Stainless Steel ◽  
Selective Laser Melting ◽  
Three Dimensional ◽  
Element Model ◽  
Laser Melting ◽  
Melt Pool ◽  
Simulation Results ◽  
Melt Pool Size ◽  
Overlap Rate ◽  
Hatch Spacing

In this study, a combined simulation and experimental approach is utilized to investigate the influence of hatch spacing on the microstructure and as-built quality of 316L stainless steel (SS) samples fabricated by selective laser melting (SLM). A three-dimensional finite element model (FEM) is employed to investigate heat transfer and melt pool during the SLM of 316L SS. The phase transformation and variation of the thermo-physical properties of the materials are considered in this model. The effects of hatch spacing (H) on the temperature field, microstructure and melt pool size, overlap rate, surface quality, and relative density during the SLM of 316L SS are investigated. The simulated results indicate that, as the hatch spacing increases, the depth increases and the width of the melt pool decreases. Meanwhile, with the increase of hatch spacing, the simulated temperature of the subsequent tracks falls below the melting temperature of the first track. Moreover, the microstructures were found to coarsen with the increasing hatch spacing due to the reduced cooling rate. The optimized hatch spacing and overlap rate between adjacent tracks were obtained from numerical simulations. Simulation results illustrate that, when the optimized hatch spacing of 100 μm is adopted, fully dense parts with a smooth surface can be fabricated by SLM, thus experimentally validating the simulation results.

Characterization of laser spatter and condensate generated during the selective laser melting of 304L stainless steel powder

2020 ◽  
Vol 31 ◽  
pp. 100904 ◽  
Author(s):  
Austin T. Sutton ◽  
Caitlin S. Kriewall ◽  
Ming C. Leu ◽  
Joseph W. Newkirk ◽  
Ben Brown
Keyword(s):  
Stainless Steel ◽  
Selective Laser Melting ◽  
Steel Powder ◽  
Stainless Steel Powder ◽  
304L Stainless Steel ◽  
Laser Melting

Thermal Modeling of 304L Stainless Steel for Selective Laser Melting: Laser Power Input Evaluation

2017 ◽  
Author(s):  
Diego Augusto de Moraes ◽  
Aleksander Czekanski
Keyword(s):  
Stainless Steel ◽  
Temperature Distribution ◽  
Selective Laser Melting ◽  
Laser Power ◽  
Laser Scanning ◽  
Power Input ◽  
304L Stainless Steel ◽  
Laser Melting ◽  
Powder Bed ◽  
The Impact

Selective Laser Melting (SLM) process is a Powder Bed Fusion (PBF) technique, which has shown significantly growth in the recent years. The demand for this process is justified by the versatility and ease in manufacturing the parts from 3D models as well for the increased complexity of engineered parts generated from topology or shape optimization. Automotive, aerospace, medical and aviation industries are taking great advantage of this process due the unique geometry characteristics found in the components. To enhance the benefits of SLM, a vital task is to analyze the laser power input impact on the temperature distribution through the powder bed, important for posterior residual stresses analysis. The Finite Element Method proposed in this study is a transient thermal model, able to predict temperature distribution through different sections of the powder bed when performing a single track of the laser scanning. Furthermore, the impact of the laser power input is carried out utilizing SS 304L, a low cost Stainless Steel alloy that can be employed in the SLM process, in order to determine the influence on the temperature distribution along the different cross sections.

scholarly journals Effect of process parameters on the microstructure and mechanical properties of AA2024 fabricated using selective laser melting

2020 ◽  
Vol 112 (1-2) ◽  
pp. 175-192
Author(s):  
Mulla Ahmet Pekok ◽  
Rossitza Setchi ◽  
Michael Ryan ◽  
Quanquan Han ◽  
Dongdong Gu
Keyword(s):  
Mechanical Properties ◽  
Selective Laser Melting ◽  
Scanning Speed ◽  
High Energy ◽  
Incomplete Fusion ◽  
Laser Melting ◽  
Melt Pool ◽  
2024 Alloy ◽  
Manufacturing Techniques ◽  
Melt Pool Size

AbstractSelective laser melting (SLM) offers significant benefits, including geometric freedom and rapid production, when compared with traditional manufacturing techniques. However, the materials available for SLM production remain limited, restricting the industrial adoption of the technology. The mechanical properties and microstructure of many aluminium alloys have not been fully explored, as their manufacturability using SLM is extremely challenging. This study investigates the effect of laser power, hatch spacing and scanning speed on the mechanical and microstructural properties of as-fabricated aluminium 2024 alloy (AA2024) manufactured using SLM. The results reveal that almost crack-free structures with high relative density (99.9%) and Archimedes density (99.7%) have been achieved. It is shown that when using low energy density (ED) levels, large cracks and porosities are a major problem, owing to incomplete fusion; however, small gas pores are prevalent at high-energy densities due to the dissolved gas particles in the melt pool. An inversely proportional relationship between ED and microhardness has also been observed. Lower ED decreases the melt pool size and temperature gradients but increases the cooling rate, creating a fine-grained microstructure, which restricts dislocation movement, therefore increasing the microhardness. The highest microhardness (116 HV0.2), which was obtained from one of the lowest EDs used (100 J/mm3), is 45% higher than as-cast AA2024-0, but 17% lower than wrought AA2024-T6 alloy.

Numerical Investigation of Selective Laser Melting Process for 904L Stainless Steel

2012 ◽  
Author(s):  
Miranda Fateri ◽  
Andreas Gebhardt ◽  
Maziar Khosravi
Keyword(s):  
Heat Flux ◽  
Stainless Steel ◽  
Selective Laser Melting ◽  
Melting Process ◽  
Full Density ◽  
Laser Melting ◽  
Scanning Velocity ◽  
Selective Laser Melting Process ◽  
Fine Mesh ◽  
Melt Pool

Selective Laser Melting process (SLM) is an important manufacturing method for producing complex geometries which allows for creation of full density parts with similar properties as the bulk material without extensive post processing. In SLM process, laser power, beam focus diameter, and scanning velocity must be precisely set based on the material properties in order to produce dense parts. In this study, Finite Element Analysis (FEA) method is employed in order to simulate and analyze a single layer of 904L Stainless Steel. A three-dimensional transient thermal model of the SLM process based on phase change enthalpy, irradiation scattering, and heat conductivity of powder is developed. The laser beam is modeled as a moving heat flux on the surface of the layer using a fine mesh which allows for a variation of the shape and distribution of the beam. In this manner, various Gaussian distributions are investigated and compared against single and multi-element heat flux sources. The melt pool and temperature distribution in the part are numerically investigated in order to determine the effects of varying laser intensity, scanning velocity as well as preheating temperature. The results of the simulation are verified by comparing the melt pool width as a function of power and velocity against the experimentally obtained results. Lastly, 3D objects are fabricated with a SLM 50 Desktop machine using the acquired optimized process parameters.

Finite Element Analysis to Improve the Accuracy of Parts Made by Stainless Steel 316L Material Using Selective Laser Melting Technology

2014 ◽  
Vol 657 ◽  
pp. 236-240 ◽  
Author(s):  
Razvan Păcurar ◽  
Ancuţa Păcurar
Keyword(s):  
Finite Element ◽  
Stainless Steel ◽  
Selective Laser Melting ◽  
Thermal Stresses ◽  
Melting Process ◽  
Optimum Process ◽  
Stainless Steel 316L ◽  
Laser Melting ◽  
Element Analysis ◽  
Bed Temperature

One of the serious problems in the SLM process, using metallic powders is the thermal distortion of the model during forming. As a result of the locally concentrated energy input, the temperature gradient mechanism and the related processes lead to residual stresses and part deformations. Since the solidified part is cooled rapidly, the model tends to be deformed and cracked due to the thermal stresses. All these aspects were considered for a series of analyses that were made using the finite element method in order to determine the optimum process parameters (laser power, scanning speed, powder bed temperature) that are required in order to improve the accuracy of the metallic parts made by Stainless Steel 316L material using the Selective Laser Melting process.

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