scholarly journals Coated Metal Powders for Laser Powder Bed Fusion (L-PBF) Processing: A Review

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1831
Author(s):  
Robert Bidulsky ◽  
Federico Simone Gobber ◽  
Jana Bidulska ◽  
Marta Ceroni ◽  
Tibor Kvackaj ◽  
...  
Keyword(s):  
Physical Properties ◽  
Powder Bed Fusion ◽  
Metal Powders ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
The Past ◽  
Coated Metal ◽  
Mechanical And Physical Properties ◽  
Interesting Approach ◽  
Coating Methods

In the last years, functionalized powders are becoming of increasing interest in additive manufacturing (particularly in laser powder bed fusion processing, L-PBF), due to their improved flowability and enhanced processability, particularly in terms of laser absorbance. Functionalized powders may also provide higher final mechanical or physical properties in the manufactured parts, like an increased hardness, a higher tensile strength, and density levels close to theoretical. Coatings represent a possible interesting approach for powders’ functionalizing. Different coating methods have been studied in the past years, either mechanical or non-mechanical. This work aims to present an overview of the currently obtained coated powders, analyzing in detail the processes adopted for their production, the processability of the coated systems, and the mechanical and physical properties of the final parts obtained by using L-PBF for the powders processing.

On Characterizing Uncertainty Sources in Laser Powder Bed Fusion Additive Manufacturing Models

2021 ◽  
Author(s):  
Tesfaye Moges ◽  
Kevontrez Jones ◽  
Shaw Feng ◽  
Paul Witherell ◽  
Gaurav Ameta
Keyword(s):  
Additive Manufacturing ◽  
Computational Models ◽  
Predictive Accuracy ◽  
Powder Bed Fusion ◽  
Metal Powders ◽  
Laser Powder Bed Fusion ◽  
Powder Morphology ◽  
Powder Bed ◽  
Uncertainty Sources ◽  
Ontology Language

Abstract Tremendous efforts have been made to use computational models of, and simulation models of, Additive Manufacturing (AM) processes. The goals of these efforts are to better understand process complexities and to realize better, high-quality parts. However, understanding whether any model is a correct representation for a given scenario is a difficult proposition. For example, when using metal powders, the laser powder bed fusion (L-PBF) process involves complex physical phenomena such as powder morphology, heat transfer, phase transformation, and fluid flow. Models based on these phenomena will possess different degrees of fidelity since they often rely on assumptions that may neglect or simplify process physics, resulting in uncertainties in their prediction accuracy. Predictive accuracy and its characterization can vary greatly between models due to their uncertainties. This paper characterizes several sources of L-PBF model uncertainty for low, medium, and high-fidelity thermal models including modeling assumptions (model-form uncertainty), numerical approximations (numerical uncertainty), and input parameters (parameter uncertainty). This paper focuses on the input uncertainty sources, which we model in terms of a probability density function (PDF), and its propagation through all other L-PBF models. We represent uncertainty sources using the Web Ontology Language (OWL), which allows us to capture the relevant knowledge used for interoperability and reusability. The topology and mapping of the uncertainty sources establish fundamental requirements for measuring model fidelity and for guiding the selection of a model suitable for its intended purpose.

scholarly journals Spreadability of Metal Powders for Laser-Powder Bed Fusion via Simple Image Processing Steps

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 205
Author(s):  
Cekdar Vakifahmetoglu ◽  
Beyza Hasdemir ◽  
Lisa Biasetto
Keyword(s):  
Image Processing ◽  
Processing Parameters ◽  
Angle Of Repose ◽  
Structural Defects ◽  
Powder Size ◽  
Powder Bed Fusion ◽  
Metal Powders ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
3D Printed

This paper investigates the spreadability of the spherical CoCrWMo powder for laser- powder bed fusion (PBF-LB) by using image processing algorithms coded in MATLAB. Besides, it also aims to examine the spreadability dependence with the other characteristics such as powder size distribution, apparent density, angle of repose. Powder blends in four different particle size distributions are prepared, characterized, and spreadability tests are performed with the PBF-LB. The results demonstrate that an increase in fine particle ratio by volume (below 10 µm) enhances the agglomeration and decreases the flowability, causing poor spreadability. These irregularities on the spread layers are quantified with simple illumination invariant analysis. A clear relation between powder spreadability and 3D printed structures properties in terms of residual porosity could not be defined since structural defects in 3D printed parts also depends on other processing parameters such as spatter formation or powder size over layer height ratio.

Numerical Modeling of Powder Gas Interaction for Laser Powder Bed Fusion Process

2020 ◽  
Author(s):  
Xuxiao Li ◽  
Wenda Tan
Keyword(s):  
Flow Field ◽  
Gas Flow ◽  
Driving Forces ◽  
Current Model ◽  
Quantitative Information ◽  
Powder Bed Fusion ◽  
Metal Powders ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Free Jet

Abstract The powder motion induced by the gas flow has been identified as one of the critical phenomena in laser powder bed fusion processes that significantly affects the build quality. However, the gas dynamics and its induced driving forces for the powder motions have not been well quantified. A numerical model is developed to investigate such powder-gas interactions. With a combination of computational fluid dynamics and particle tracking techniques, the model is capable of simulating the transient gas flow field surrounding the powder and the forces exerted on powder surfaces. The interaction between metal powders and a free jet is investigated with the current model. In the simulation results, the entrainment and the ejection motions of powders with respect to the free jet can be predicted. It is found that the driving forces of these motions are majorly contributed by the pressure differences in the gas flow surrounding the powder, and the powders can also interact with the jet to significantly alter the flow field. Quantities which are difficult to measure by experiments are quantified by the simulations, such as the velocity and pressure field in the gas, as well as the subjected forces and torques of powders. Such quantitative information provides insights to the mechanisms of the powder-gas interaction in laser powder bed fusion processes.

Numerical Modeling of Powder Gas Interaction Relative to Laser Powder Bed Fusion Process

2020 ◽  
Vol 143 (5) ◽  
Author(s):  
Xuxiao Li ◽  
Wenda Tan
Keyword(s):  
Flow Field ◽  
Gas Flow ◽  
Driving Forces ◽  
Current Model ◽  
Quantitative Information ◽  
Powder Bed Fusion ◽  
Metal Powders ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Free Jet

Abstract The powder motion induced by the gas flow has been identified as one of the critical phenomena in laser powder bed fusion processes that significantly affect the build quality. However, the gas dynamics and its induced driving forces for the powder motions have not been well quantified. A numerical model is developed to investigate such powder-gas interactions. With a combination of computational fluid dynamics and particle tracking techniques, the model is capable of simulating the transient gas flow field surrounding the powder and the forces exerted on powder surfaces. The interaction between metal powders and a free jet is investigated with the current model. In the simulation results, the entrainment and the ejection motions of powders with respect to the free jet can be predicted. It is found that the driving forces of these motions are majorly contributed by the pressure differences in the gas flow surrounding the powder, and the powders can also interact with the jet to significantly alter the flow field. Quantities that are difficult to measure by experiments are quantified by the simulations, such as the velocity/pressure fields in the gas as well as the subjected forces and torques on powders. Such quantitative information provides insights about the mechanisms of the powder-gas interaction in laser powder bed fusion processes.

scholarly journals On the Relevance of Volumetric Energy Density in the Investigation of Inconel 718 Laser Powder Bed Fusion

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 538 ◽  
Author(s):  
Fabrizia Caiazzo ◽  
Vittorio Alfieri ◽  
Giuseppe Casalino
Keyword(s):  
Surface Roughness ◽  
Energy Density ◽  
Process Parameters ◽  
Vickers Hardness ◽  
Powder Bed Fusion ◽  
Processing Conditions ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Fractional Density ◽  
Experimental Variation

Laser powder bed fusion (LPBF) can fabricate products with tailored mechanical and surface properties. In fact, surface texture, roughness, pore size, the resulting fractional density, and microhardness highly depend on the processing conditions, which are very difficult to deal with. Therefore, this paper aims at investigating the relevance of the volumetric energy density (VED) that is a concise index of some governing factors with a potential operational use. This paper proves the fact that the observed experimental variation in the surface roughness, number and size of pores, the fractional density, and Vickers hardness can be explained in terms of VED that can help the investigator in dealing with several process parameters at once.

Heat source model calibration for thermal analysis of laser powder-bed fusion

2020 ◽  
Vol 106 (7-8) ◽  
pp. 3367-3379 ◽  
Author(s):  
Shahriar Imani Shahabad ◽  
Zhidong Zhang ◽  
Ali Keshavarzkermani ◽  
Usman Ali ◽  
Yahya Mahmoodkhani ◽  
...  
Keyword(s):  
Thermal Analysis ◽  
Heat Source ◽  
Model Calibration ◽  
Source Model ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Heat Source Model ◽  
Powder Bed
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