Laser Interaction with Surface in Powder Bed Melting Process and Its Impact on Temperature Profile, Bead and Melt Pool Geometry

2019 ◽  
pp. 319-329 ◽  
Author(s):  
Leila Ladani ◽  
Faiyaz Ahsan
Keyword(s):  
Temperature Profile ◽  
Melting Process ◽  
Laser Interaction ◽  
Powder Bed ◽  
Melt Pool

scholarly journals Pyrometric-Based Melt Pool Monitoring Study of CuCr1Zr Processed Using L-PBF

Materials ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 4626
Author(s):  
Katia Artzt ◽  
Martin Siggel ◽  
Jan Kleinert ◽  
Joerg Riccius ◽  
Guillermo Requena ◽  
...  
Keyword(s):  
Stable Process ◽  
Melting Process ◽  
Quality Monitoring ◽  
Powder Bed ◽  
Part Geometry ◽  
Melt Pool ◽  
Process Understanding ◽  
Reducing Costs ◽  
Non Destructive

The potential of in situ melt pool monitoring (MPM) for parameter development and furthering the process understanding in Laser Powder Bed Fusion (LPBF) of CuCr1Zr was investigated. Commercial MPM systems are currently being developed as a quality monitoring tool with the aim of detecting faulty parts already in the build process and, thus, reducing costs in LPBF. A detailed analysis of coupon specimens allowed two processing windows to be established for a suitably dense material at layer thicknesses of 30 µm and 50 µm, which were subsequently evaluated with two complex thermomechanical-fatigue (TMF) panels. Variations due to the location on the build platform were taken into account for the parameter development. Importantly, integrally averaged MPM intensities showed no direct correlation with total porosities, while the robustness of the melting process, impacted strongly by balling, affected the scattering of the MPM response and can thus be assessed. However, the MPM results, similar to material properties such as porosity, cannot be directly transferred from coupon specimens to components due to the influence of the local part geometry and heat transport on the build platform. Different MPM intensity ranges are obtained on cuboids and TMF panels despite similar LPBF parameters. Nonetheless, besides identifying LPBF parameter windows with a stable process, MPM allowed the successful detection of individual defects on the surface and in the bulk of the large demonstrators and appears to be a suitable tool for quality monitoring during fabrication and non-destructive evaluation of the LPBF process.

Finite Element Thermal Analysis of Melt Pool in Selective Laser Melting Process

2018 ◽  
Author(s):  
Zhibo Luo ◽  
Yaoyao Fiona Zhao
Keyword(s):  
Heat Source ◽  
Selective Laser Melting ◽  
Computational Cost ◽  
Melting Process ◽  
Point Heat Source ◽  
Laser Melting ◽  
Line Heat Source ◽  
Powder Bed ◽  
Melt Pool ◽  
Gaussian Point

Selective laser melting is one of the powder bed fusion processes which fabricates a part through layer-wised method. Due to the ability to build a customized and complex part, selective laser melting process has been broadly studied in academic and applied in industry. However, rapidly changed thermal cycles and extremely high-temperature gradients among the melt pool induce a periodically changed thermal stress in solidified layers and finally result in a distorted part. Therefore, the temperature distribution in the melt pool and the size and shape of the melt pool directly determine the mechanical and geometrical property of final part. As experimental trial-and-error method takes a huge amount of cost, different numerical methods have been adopted to estimate the transient temperature and thermal stress distribution in the melt pool and powder bed. The most existing research utilizes the moving Gaussian point heat source to model the profile of the melt pool, which consumes a significant amount of computational cost and cannot be used to implement the part-level simulation. This research proposes a new line heat source to replace the moving point heat source. Some efforts are applied to reduce the computational cost. Specifically, a relatively large step size is used for the line heat source to reduce the number of time steps. In addition, a mesh refinement scheme is adopted to reduce the number of cells in each time step by refining the mesh close to the heat source and coarsening the mesh far away from it. On the other hand, efforts are implemented to increase the accuracy of the simulation result. Temperature-dependent material properties are considered in this FE framework. In addition, material transition among powder, liquid, and solid are incorporated in the developed FE framework. In this study, temperature simulation of one scanning track based on self-developed FE code is applied for Stainless Steel 316L. The simulation results show that the temperature distribution and history of melt pool within line heat source are comparable to that of the moving Gaussian point heat source. While the simulation time is reduced by more than two times depending on the length of line heat input. Therefore, this FE model can be used to numerically investigate the process parameters and help to control the quality of the final part.

Multi-Physics Modeling of Laser Interaction With Surface in Powder Bed Melting Process

2018 ◽  
Author(s):  
Faiyaz Ahsan ◽  
Jafar Razmi ◽  
Leila Ladani
Keyword(s):  
Heat Source ◽  
Melting Process ◽  
Moving Heat Source ◽  
Laser Interaction ◽  
Power Absorption ◽  
Powder Bed ◽  
Physical Mechanisms ◽  
The Past ◽  
Physics Modeling ◽  
Metal Additive

Powder bed metal additive manufacturing process using laser or electron beam heat source is gaining increasing popularity due to its ability to create complex shaped metallic components. The process is a complex multi-physics process where multiple phases of material exist and laser interacts through multiple physical mechanisms with the surface of these materials and phases. The power absorption depends on optical and thermos-physical properties of the surface and laser type and wavelength. Most of the work conducted in the past have modeled the laser using a moving heat source. These studies typically assume a certain absorption without actual calculation of this power absorption. This study focuses on modeling the process in a more comprehensive manner including the laser physics and evaluating how this physics affects the temperature distribution and build outcome. The results are compared with the conventional techniques where simple Gaussian distribution was used for the power source. The temperature profile obtained with this study was lower than the Gaussian beam.

scholarly journals Investigation of SLM Process in Terms of Temperature Distribution and Melting Pool Size: Modeling and Experimental Approaches

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1272 ◽  
Author(s):  
Md Jonaet Ansari ◽  
Dinh-Son Nguyen ◽  
Hong Seok Park
Keyword(s):  
Temperature Distribution ◽  
3D Printing ◽  
Temperature Profile ◽  
Pool Size ◽  
Large Temperature ◽  
Thermal Imager ◽  
Powder Bed ◽  
Melt Pool ◽  
Melting Pool ◽  
Melt Pool Size

Selective laser melting (SLM) is an additive manufacturing (AM) technique that has the potential to produce almost any three-dimensional (3D) metallic part, even those with complicated shapes. Throughout the SLM process, the heat transfer characteristics of the metal powder plays a significant role in maintaining the product quality during 3D printing. Thus, it is crucial for 3D-printing manufacturers to determine the thermal behavior over the SLM process. However, it is a significant challenge to accurately determine the large temperature gradient and the melt pool size using only experiments. Therefore, the use of both experimental investigations and numerical analysis can assist in characterizing the temperature evaluation and the melt pool size in a more effective manner. In this study, 3D finite element analysis applying a moving volumetric Gaussian laser heat source was used to analyze the temperature profile on the powder bed and the resultant melt pool size throughout the SLM process. In the experiments, a TELOPS FAST-IR (M350) thermal imager was applied to determine the temperature profile of the melting pool and powder bed along the scanning direction during the SLM fabrication using Ti6Al4V powder. The numerically calculated results were compared with the experimentally determined temperature distribution. The comparison showed that the calculated peak temperature for single- and multi-track by the developed thermal model was in good agreement with the experiment results. Secondly, the developed model was verified by comparing the melting pool size for various laser powers and scanning speeds with the experimentally measured melting pool size from the published literature. The developed model could predict the melt pool width (with 2–5% error) and melt pool depth (with 5–6% error).

Thermal Behavior and Melt-Pool Dynamics of Cu-Cr-Zr Alloy in Powder-Bed Selective Laser Melting Process

2019 ◽  
Author(s):  
M. Shafiqur Rahman ◽  
Paul J. Schilling ◽  
Paul D. Herrington ◽  
Uttam K. Chakravarty
Keyword(s):  
Thermal Behavior ◽  
Selective Laser Melting ◽  
Melting Process ◽  
Rate Variation ◽  
Cfd Model ◽  
Laser Melting ◽  
Powder Bed ◽  
Melt Pool ◽  
Functional Components ◽  
Zr Alloy

Abstract Selective laser melting (SLM) is a growing additive manufacturing (AM) technology which is capable of rapidly fabricating functional components in the medical and aviation industries. The thermophysical properties and melt-pool dynamics involved in the powder-bed SLM process play a crucial role to determine the part quality and process optimization. In this study, a 3-D computational fluid dynamics (CFD) model with Cu-Cr-Zr (C-18150) powder-bed is developed incorporating a moving conical volumetric heat source and temperature-dependent thermal properties to conduct the Multiphysics simulations of the SLM process. The melt-pool dynamics and its thermal behavior are investigated numerically and results for temperature profile, cooling rate, variation in density, thermal conductivity, specific heat capacity, and velocity in the melt pool are obtained for different laser beam specifications. The validation of the CFD model is conducted by comparing the simulation results for temperature and the melt-front motion with the analytical results found from the classical Stefan problem of the phase-change material. Studying the process parameters, melt-pool geometry, and thermal behavior of Cu-Cr-Zr alloy can generate valuable information to establish Cu-Cr-Zr as a low-cost engineering material in the AM industry.

scholarly journals The effects of locations on the build tray on the quality of specimens in powder bed additive manufacturing

2021 ◽  
Author(s):  
Snehashis Pal ◽  
Nenad Gubeljak ◽  
Tonica Bončina ◽  
Radovan Hudák ◽  
Teodor Toth ◽  
...  
Keyword(s):  
Main Role ◽  
Particle Sizes ◽  
Additional Experiment ◽  
Powder Bed ◽  
Melt Pool ◽  
Start Line ◽  
Sample Density ◽  
Powder Layering ◽  
Pool Formation

AbstractIn this study, the effect of powder spreading direction was investigated on selectively laser-melted specimens. The results showed that the metallurgical properties of the specimens varied during fabrication with respect to their position on the build tray. The density, porosity, and tensile properties of the Co–Cr–W–Mo alloy were investigated on cuboid and tensile specimens fabricated at different locations. Two different significant positions on the tray were selected along the powder spreading direction. One set of specimens was located near the start line of powder spreading, and the other set was located near the end of the building tray. The main role in the consequences of powder layering was played by the distribution of powder particle sizes and the packing density of the layers. As a result, laser penetration, melt pool formation, and fusion characteristics varied. To confirm the occurrence of variations in sample density, an additional experiment was performed with a Ti–6Al–4V alloy. Furthermore, the powders were collected at two different fabricating locations and their size distribution for both materials was investigated.

scholarly journals Process characterization and analysis of ceramic powder bed fusion

2021 ◽  
Author(s):  
Kevin Florio ◽  
Dario Puccio ◽  
Giorgio Viganò ◽  
Stefan Pfeiffer ◽  
Fabrizio Verga ◽  
...  
Keyword(s):  
High Speed ◽  
Ceramic Powder ◽  
Integrating Sphere ◽  
Alumina Powder ◽  
Powder Bed Fusion ◽  
Single Track ◽  
Ceramic Powders ◽  
Pure Alumina ◽  
Powder Bed ◽  
Melt Pool

AbstractPowder bed fusion (PBF) of ceramics is often limited because of the low absorptance of ceramic powders and lack of process understanding. These challenges have been addressed through a co-development of customized ceramic powders and laser process capabilities. The starting powder is made of a mix of pure alumina powder and alumina granules, to which a metal oxide dopant is added to increase absorptance. The performance of different granules and process parameters depends on a large number of influencing factors. In this study, two methods for characterizing and analyzing the PBF process are presented and used to assess which dopant is the most suitable for the process. The first method allows one to analyze the absorptance of the laser during the melting of a single track using an integrating sphere. The second one relies on in-situ video imaging using a high-speed camera and an external laser illumination. The absorption behavior of the laser power during the melting of both single tracks and full layers is proven to be a non-linear and extremely dynamic process. While for a single track, the manganese oxide doped powder delivers higher and more stable absorptance. When a full layer is analyzed, iron oxide-doped powder is leading to higher absorptance and a larger melt pool. Both dopants allow the generation of a stable melt-pool, which would be impossible with granules made of pure alumina. In addition, the present study sheds light on several phenomena related to powder and melt-pool dynamics, such as the change of melt-pool shape and dimension over time and powder denudation effects.

scholarly journals Optimization of Laser Powder Bed Fusion Processing Using a Combination of Melt Pool Modeling and Design of Experiment Approaches: Density Control

2019 ◽  
Vol 3 (1) ◽  
pp. 21 ◽  
Author(s):  
Morgan Letenneur ◽  
Alena Kreitcberg ◽  
Vladimir Brailovski
Keyword(s):  
Scanning Speed ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Density Prediction ◽  
Melt Pool ◽  
Density Control ◽  
Pool Model ◽  
Conventional Material ◽  
Prediction Approach

A simplified analytical model of the laser powder bed fusion (LPBF) process was used to develop a novel density prediction approach that can be adapted for any given powder feedstock and LPBF system. First, calibration coupons were built using IN625, Ti64 and Fe powders and a specific LPBF system. These coupons were manufactured using the predetermined ranges of laser power, scanning speed, hatching space, and layer thickness, and their densities were measured using conventional material characterization techniques. Next, a simplified melt pool model was used to calculate the melt pool dimensions for the selected sets of printing parameters. Both sets of data were then combined to predict the density of printed parts. This approach was additionally validated using the literature data on AlSi10Mg and 316L alloys, thus demonstrating that it can reliably be used to optimize the laser powder bed metal fusion process.

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