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Influence of Process Parameters and Deposition Strategy on Laser Metal Deposition of 316L Powder
摘要： In blown powder additive manufacturing technologies the geometrical stability of the built parts is more complex with respect to more conventional powder bed processes. Because of this reason, in order to select the most suitable building parameters, it is important to investigate the shape and the properties of the single metal bead formation and the effect that a scan track has on the nearby ones. In the present study, a methodology to identify an appropriate laser metal deposition process window was introduced, and the effect of the building parameters on the geometry of circular steel samples was investigated. The effect of the scanning strategy on the deposited part was also investigated. This work draws the attention to the importance of the obtainment of the most suitable melt pool shape, demonstrating that the laser power and the scanning strategy have a strong influence not only on the shape but also on the mechanical properties of the final component.
关键词： steel,additive manufacturing,melt pool,overlap,scanning strategy,directed energy deposition,AISI 316L
更新于2025-09-16 10:30:52
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Effects of laser additive manufacturing on microstructure and crystallographic texture of austenitic and martensitic stainless steels
摘要： Powder-fed laser additive manufacturing (LAM) based on directed energy deposition (DED) technology is used to produce S316-L austenitic, and S410-L martensitic stainless steel structures by 3D-printing through a layer-upon-layer fashion. The microstructural features and crystallographic textural components are studied via electron backscattering diffraction (EBSD) analysis, hardness indentation and tensile testing. The results are compared with commercial rolled sheets of austenitic and martensitic stainless steels. A well-developed <100> direction solidification texture (with a J-index of ~11.5) is observed for the austenitic structure produced by the LAM process, compared to a J-index of ~2.0 for the commercial austenitic rolled sheet. Such a texture in the LAM process is caused by equiaxed grain formation in the middle of each layer followed by columnar growth during layer-upon-layer deposition. A quite strong preferred orientation (J-index of 17.5) is noticed for martensitic steel developed by LAM. Large laths of martensite exhibit a dominant textural component of <011>//{111} in the α-phase, which is mainly controlled by transformation during layer-by-layer deposition. On the other hand, the martensitic commercial sheet consists of equiaxed grains without any preferred orientation or completely random orientations. In the case of the austenitic steel, mechanical properties such as tensile strength, hardness and ductility were severely deteriorated during the LAM deposition. A ductility loss of about 50% is recorded compared to the commercially rolled sheets that is attributed to the cast/solidified structure. However, LAM manufacturing of martensitic stainless steel structures leads to a considerably enhanced mechanical strength (more than double) at the expense of reduced ductility, because of martensitic phase transformations under higher cooling rates.
关键词： Directed energy deposition (DED),Laser additive manufacturing (LAM),Crystallographic texture,S316-L austenitic stainless steel,S410-L martensitic stainless steel
更新于2025-09-12 10:27:22
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Coaxial laser triangulation for height monitoring in laser metal deposition
摘要： The control of the height parameter plays a crucial role in the laser metal deposition (LMD) process. A mismatch between the deposition height increment and the process growth rate can generate geometrical inaccuracies as well as collisions. The paper presents a method based on triangulation for monitoring in-line the height on a LMD system composed of a coaxial deposition head, an anthropomorphic robot and a fiber laser. The measurement device is implemented within the deposition head, with a probe laser beam that is launched coaxially through the nozzle and focused directly on the melt pool at different positions depending on the standoff distance. The position of the probe spot is acquired through a coaxial camera and converted in relative height values. The system is demonstrated for the distance measurement over a range of some millimeters during the deposition of AISI 316L stainless steel. This method allows for high flexibility being independent on the deposition direction.
关键词： additive manufacturing,optical monitoring,directed energy deposition,laser triangulation
更新于2025-09-12 10:27:22
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Melt Pool Size Control Through Multiple Closed-Loop Modalities in Laser-Wire Directed Energy Deposition of Ti-6Al-4V
摘要： Sensing and closed-loop control are critical attributes of a robust 3D printing process, such as Directed Energy Deposition (DED), in which it is necessary to manage geometry, material properties, and residual stress and distortion. The present research demonstrates multiple modes of closed-loop melt pool size control in laser-wire based DED, a form of large-scale metal additive manufacturing. First, real-time closed-loop melt pool size control through laser power modulation was demonstrated for intralayer control of bead geometry. Aspects such as controller tuning, response time, interaction with primary process variables, and disturbance rejection are presented. Next, an interlayer trend in laser power during the printing of layered components was documented, which inspired the development of novel modes of control. A controller that modulates print speed and deposition rate on a per-layer basis was developed and demonstrated, enabling the control of either average melt pool size alone or average laser power in coordination with real-time melt pool size control. This work demonstrates that accumulated heat in components under construction can be exploited to maintain process stability as print speed and deposition rate are automatically increased under closed-loop control. This has major implications for overall production efficiency. Control modes are characterized in terms of their effect on local bead geometry, global part geometry, and interlayer effect on energy density, among other factors.
关键词： Directed Energy Deposition,Monitoring,Metal,Closed-Loop,3D Printing,Ti-6Al-4V,Lasers,Control,Additive Manufacturing,Melt Pool
更新于2025-09-12 10:27:22