scholarly journals Tungsten Fabricated by Laser Powder Bed Fusion

2021 ◽  
Author(s):  
Pietro Rebesan ◽  
Massimiliano Bonesso ◽  
Claudio Gennari ◽  
Razvan Dima ◽  
Adriano Pepato ◽  
...  
Keyword(s):  
Process Parameters ◽  
Complex Geometry ◽  
Microstructural Analysis ◽  
Refractory Metals ◽  
High Density ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
High Melting Point ◽  
Powder Bed ◽  
Regular Shape

AbstractAdditive Manufacturing (AM) is the process that allows the production of complex geometry and lightweight components. Thanks to the high density of refractory metals, AM could be a possible solution for their application in the aerospace field and for biomedical or future nuclear fusion devices. Yet, Laser Powder Bed Fusion (LPBF) of refractory metals as Ta, Mo, and W faces some challenges due to their main properties: high melting point, heat conductivity, and susceptibility to cracks.The purpose of this study is to optimize the process parameters in order to produce high-density Tungsten parts by LPBF on an EOS M100 (maximum power of 170 W). The characterization is performed through physical properties measurements and microstructural analysis. Single Scan Tracks (SSTs) are produced on the top surfaces of Tungsten blocks to evaluate the process parameters that give regular-shape and continuous melt-pools. Both analytical and experimental optimizations of process parameters were performed. Micro-hardness measurements were done for dense bulk specimens. Finally, a description of susceptibility to cracks of additively manufactured Tungsten was performed.

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.

scholarly journals Comparison of Phase Characteristics and Residual Stresses in Ti-6Al-4V Alloy Manufactured by Laser Powder Bed Fusion (L-PBF) and Electron Beam Powder Bed Fusion (EB-PBF) Techniques

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 796
Author(s):  
Aya Takase ◽  
Takuya Ishimoto ◽  
Naotaka Morita ◽  
Naoko Ikeo ◽  
Takayoshi Nakano
Keyword(s):  
Electron Beam ◽  
Residual Stresses ◽  
Cooling Rate ◽  
Process Parameters ◽  
Phase Evolution ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Solidification Temperature ◽  
Powder Bed ◽  
Β Phase

Ti-6Al-4V alloy fabricated by laser powder bed fusion (L-PBF) and electron beam powder bed fusion (EB-PBF) techniques have been studied for applications ranging from medicine to aviation. The fabrication technique is often selected based on the part size and fabrication speed, while less attention is paid to the differences in the physicochemical properties. Especially, the relationship between the evolution of α, α’, and β phases in as-grown parts and the fabrication techniques is unclear. This work systematically and quantitatively investigates how L-PBF and EB-PBF and their process parameters affect the phase evolution of Ti-6Al-4V and residual stresses in the final parts. This is the first report demonstrating the correlations among measured parameters, indicating the lattice strain reduces, and c/a increases, shifting from an α’ to α+β or α structure as the crystallite size of the α or α’ phase increases. The experimental results combined with heat-transfer simulation indicate the cooling rate near the β transus temperature dictates the resulting phase characteristics, whereas the residual stress depends on the cooling rate immediately below the solidification temperature. This study provides new insights into the previously unknown differences in the α, α’, and β phase evolution between L-PBF and EB-PBF and their process parameters.

scholarly journals Role of laser powder bed fusion process parameters in crystallographic texture of additive manufactured Nb-48Ti alloy

2021 ◽  
Author(s):  
Rafael de Moura Nobre ◽  
Willy Ank de Morais ◽  
Matheus Tavares Vasques ◽  
Jhoan Guzmán ◽  
Daniel Luiz Rodrigues Junior ◽  
...  
Keyword(s):  
Process Parameters ◽  
Crystallographic Texture ◽  
Fusion Process ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed

scholarly journals Laser Powder Bed Fusion Processing of Fe-Mn-Al-Ni Shape Memory Alloy—On the Effect of Elevated Platform Temperatures

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 185
Author(s):  
Felix Clemens Ewald ◽  
Florian Brenne ◽  
Tobias Gustmann ◽  
Malte Vollmer ◽  
Philipp Krooß ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Crack Formation ◽  
Microstructural Analysis ◽  
Tensile Load ◽  
Grain Structure ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Cyclic Heat Treatment ◽  
Powder Bed ◽  
Cyclic Heat

In order to overcome constraints related to crack formation during additive processing (laser powder bed fusion, L-BPF) of Fe-Mn-Al-Ni, the potential of high-temperature L-PBF processing was investigated in the present study. The effect of the process parameters on crack formation, grain structure, and phase distribution in the as-built condition, as well as in the course of cyclic heat treatment was examined by microstructural analysis. Optimized processing parameters were applied to fabricate cylindrical samples featuring a crack-free and columnar grained microstructure. In the course of cyclic heat treatment, abnormal grain growth (AGG) sets in, eventually promoting the evolution of a bamboo like microstructure. Testing under tensile load revealed a well-defined stress plateau and reversible strains of up to 4%.

scholarly journals Optimizing Laser Powder Bed Fusion Parameters for IN-738LC by Response Surface Method

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4879
Author(s):  
Mireia Vilanova ◽  
Rubén Escribano-García ◽  
Teresa Guraya ◽  
Maria San Sebastian
Keyword(s):  
Response Surface ◽  
Response Surface Method ◽  
Process Parameters ◽  
Crack Density ◽  
Processing Parameters ◽  
Optimum Process ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Surface Method

A method to find the optimum process parameters for manufacturing nickel-based superalloy Inconel 738LC by laser powder bed fusion (LPBF) technology is presented. This material is known to form cracks during its processing by LPBF technology; thus, process parameters have to be optimized to get a high quality product. In this work, the objective of the optimization was to obtain samples with fewer pores and cracks. A design of experiments (DoE) technique was implemented to define the reduced set of samples. Each sample was manufactured by LPBF with a specific combination of laser power, laser scan speed, hatch distance and scan strategy parameters. Using the porosity and crack density results obtained from the DoE samples, quadratic models were fitted, which allowed identifying the optimal working point by applying the response surface method (RSM). Finally, five samples with the predicted optimal processing parameters were fabricated. The examination of these samples showed that it was possible to manufacture IN738LC samples free of cracks and with a porosity percentage below 0.1%. Therefore, it was demonstrated that RSM is suitable for obtaining optimum process parameters for IN738LC alloy manufacturing by LPBF technology.

scholarly journals A study on surface morphology and tension in laser powder bed fusion of Ti-6Al-4V

2020 ◽  
Vol 111 (9-10) ◽  
pp. 2891-2909
Author(s):  
Mahyar Khorasani ◽  
AmirHossein Ghasemi ◽  
Umar Shafique Awan ◽  
Elahe Hadavi ◽  
Martin Leary ◽  
...  
Keyword(s):  
Surface Tension ◽  
Process Parameters ◽  
Surface Profile ◽  
Test Case ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Data Set ◽  
Powder Bed ◽  
Case Morphology ◽  
Melting Pool

Abstract When reporting surface quality, the roughest surface is a reference for the measurements. In LPBF due to recoil pressure and scan movement, asymmetric surface is shaped, and surface roughness has different values in different measurement orientations. In this research, the influence of the laser powder bed fusion (LPBF) process parameters on surface tension and roughness of Ti-6AI-4 V parts in three orientations are investigated. To improve the mechanical properties, heat treatment was carried out and added to the designed matrix to generate a comprehensive data set. Taguchi design of experiment was employed to print 25 samples with five process parameters and post-processing. The effect and interaction of the parameters on the formation of surface profile comprising tension, morphology and roughness in various directions have been analysed. The main contribution of this paper is developing a model to approximate the melting pool temperature and surface tension based on the process parameters. Other contributions are an analysis of process parameters to determine the formation and variation of surface tension and roughness and explain the governing mechanisms through rheological phenomena. Results showed that the main driving factors in the variation of surface tension and formation of the surface profile are thermophysical properties of the feedstock, rheology and the temperature of the melting pool. Also, the results showed that while the value of surface tension is the same for each test case, morphology and the value of roughness are different when analysing the surface in perpendicular, parallel and angled directions to laser movement.

scholarly journals An Empirical Approach for the Development of Process Parameters for Laser Powder Bed Fusion

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5400 ◽  
Author(s):  
Aron Pfaff ◽  
Martin Jäcklein ◽  
Max Schlager ◽  
Wilfried Harwick ◽  
Klaus Hoschke ◽  
...  
Keyword(s):  
Process Parameters ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Laser Track ◽  
Initial Development ◽  
Track Width ◽  
Near Surface ◽  
Powder Bed ◽  
Single Laser ◽  
Target Values

For certain additive manufacturing technologies the choice of available materials is currently limited. The development of process parameters is especially elaborate for powder bed technologies. Currently, there is no common approach concerning the procedure and documentation. This work proposes a methodology for the initial development of process parameters for new L-PBF (laser powder bed fusion) alloys. Key elements are the examination of the laser–powder-bed interaction by single laser track experiments and an iterative design of experiment (DoE) approach for the development of volumetric parameters. Two types of single laser track experiments are presented and provide information regarding the laser track width and depth as well as the resulting surface roughness and melt pool classification. Based on the information gained, suitable process windows for a DoE study can be defined by avoiding parameter settings unsuitable for production or measurement. Gradually, input variables are identified and iterative steps reduce the process window in order to optimize the desired target values. Near-surface exposure parameters are developed by a one-dimensional parameter variation and metallographic investigations. The approach is primarily designed for the initial development of process parameters for new L-PBF alloys. However, the information gained can also be used to optimize established parameter sets regarding new target values (productivity, mechanical properties), optimize process parameters for specific components or for a microstructural design.

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