Experimental Approach for Development of a Powder Spreading Metric in Additive Manufacturing

The Powder Spreading is a Vital Step of Powder-Based Additive Manufacturing (AM) Processes. the Quality of Spread Powder Can Considerably Influence the Properties of Fabricated Parts. Poorly Packed Powder Beds with High Surface Roughness Result in Printed Part Layers with Large Porosity and Low Dimensional Accuracy, Leading to Poor Mechanical Properties. Therefore, the Powder Spread ability and its Dependence on Process Parameters and Powder Characteristics Should Be Quantified to Improve the Efficiency of Powder-Based AM Methods. This Study Proposes a Novel Dimensionless Powder Spread Ability Metric that Can Be Commonly Used in Different Powder-Based AM Processes. the Quality of Spread Powder in Terms of Powder Bed Density and Surface Roughness Was Evaluated by Adjusting the Process Parameters Including Recoating Velocity and Layer Thickness, and Powder Characteristics Including Particle Size Distribution. in Addition, the Dynamic Repose Angle Was Proposed and Examined as Another Powder Spread Ability Metric. the Results Showed that These Two Proposed Metrics Were Strongly Correlated and Lower Recoating Velocity and Larger Layer Thickness Led to Higher Spread ability and Lower Dynamic Repose Angle

Characterization of Virgin, Re-Used, and Oxygen-Reduced Copper Powders Processed by the Plasma Spheroidization Process

Fabrication of parts with high mechanical properties heavily depend on the quality of powder deployed in the fabrication process. Copper powder in three different powder types were spheroidized using radio-frequency inductively coupled plasma (ICP) spheroidization process (TekSphero-15 system). The characterized powders include virgin powder as purchased from the powder manufacturer, powder used in electron beam powder bed fusion (EB-PBF) process, and reconditioned powder, which was used powder that underwent an oxygen-reduction treatment. The goal of spheroidizing these powder types was to evaluate the change in powder morphology, the possibility of enhancing the powder properties back to their as-received conditions, and assess oxygen reduction of the powder lots given their initial oxygen contents. Also, to investigate the impact of re-spheroidization on powder properties, the second round of spheroidization was performed on the already used-spheroidized powder. The impact of powder type on powder sphericity and particle size distribution was evaluated using the image analysis of scanning electron microscope (SEM) micrographs and laser diffraction, respectively. The spheroidized powder showed higher sphericity and more uniform particle size distribution overall. Depending on the powder collection bin, second round of spheroidization affected the powder sphericity differently. The possibility of deploying the plasma spheroidization process as an alternative oxygen-reduction technique was also investigated through tracking the powders\u27 oxygen content using inert gas fusion method before and after the spheroidization. The plasma spheroidized powder showed less oxygen content than the hydrogen-treated powder. The second round of spheroidization caused no change in oxygen content. The correlation between oxygen-reduction and created cracks was discussed and compared between plasma spheroidization and hydrogen-treatment. The plasma spheroidization process created a powder with higher sphericity, uniform particle size, and less oxygen content

Investigation of Mechanical Properties of Parts Fabricated with Gas- and Water-Atomized 304L Stainless Steel Powder in the Laser Powder Bed Fusion Process

The use of gas-atomized powder as the feedstock material for the laser powder bed fusion (LPBF) process is common in the additive manufacturing (AM) community. Although gas-atomization produces powder with high sphericity, its relatively expensive production cost is a downside for application in AM processes. Water atomization of powder may overcome this limitation due to its low-cost relative to the gas-atomization process. In this work, gas- and water-atomized 304L stainless steel powders were morphologically characterized through scanning electron microscopy (SEM). The water-atomized powder had a wider particle size distribution and exhibited less sphericity. Measuring powder flowability using the Revolution Powder Analyzer (RPA) indicated that the water-atomized powder had less flowability than the gas-atomized powder. Through examining the mechanical properties of LPBF fabricated parts using tensile tests, the gas-atomized powder had significantly higher yield tensile strength and elongation than the water-atomized powder; however, their ultimate tensile strengths were not significantly different

Development and Experimental Study of an Automated Laser-Foil-Printing Additive Manufacturing System

Purpose: This paper aims to present the development and experimental study of a fully automated system using a novel laser additive manufacturing technology called laser foil printing (LFP), to fabricate metal parts layer by layer. The mechanical properties of parts fabricated with this novel system are compared with those of comparable methodologies to emphasize the suitability of this process. Design/methodology/approach: Test specimens and parts with different geometries were fabricated from 304L stainless steel foil using an automated LFP system. The dimensions of the fabricated parts were measured, and the mechanical properties of the test specimens were characterized in terms of mechanical strength and elongation. Findings: The properties of parts fabricated with the automated LFP system were compared with those of parts fabricated with the powder bed fusion additive manufacturing methods. The mechanical strength is higher than those of parts fabricated by the laser powder bed fusion and directed energy deposition technologies. Originality/value: To the best knowledge of authors, this is the first time a fully automated LFP system has been developed and the properties of its fabricated parts were compared with other additive manufacturing methods for evaluation

Subduction-unrelated magmatism of southern periphery of Paleotethys: constraints from Late Paleozoic magmatism from the south of Masuleh, western Alborz

The Alborz Mountains in north of Iran correlates with the Paleotethyan Suture so preserves valuable clues for geodynamic clarifications and paleotectonic reconstructions. During life span of Paleotethys from Early Paleozoic to Late Triassic, major parts of Alborz appear as a continental margin in southern border of the oceanic basin. To test paleotectonic setting of Alborz during Late Paleozoic and its passive or active condition, geochemical data of magmatic rocks can provide useful clues. The Masuleh area (western Alborz) involves important exposures of Late Paleozoic volcanic associations. These volcanics are poorly studied and understood, so we intend to present new geochemical data about them. Field studies characterize various lithological units in tectonic and stratigraphic contact with volcanic units including Late Paleozoic low-grade metamorphics (slate-phyllite) and calcareous units of upper Devonian, Carboniferous to Permian. The whole rock geochemical data has been obtained by XRF and ICP-MS at Ferrara University, Italy. The volcanics mainly comprise basaltic to trachy-basaltic compositions. They show moderate to high alteration reflected in their LOI content (2.2 to 7.8 wt.%). Thus, for major element we used recalculated anhydrous values. The SiO2 abundances of 45.3 to 50.7 wt.% display basic nature of the studied rocks. Other major element components such as TiO2, Al2O3, CaO and MgO are in the ranges of 1-4.4, 13.7-18.3, 5-10.7 and 2.5-14.9 wt.%, respectively. Moreover, Mg# [MgO*100/(MgO+FeO*)] varies from 19-71. Wide range of major element variations likely corresponds to different modal mineralogy and also various extent of melt evolution and fractionation processes. Total alkali element abundance (Na2O+K2O) displays elevated values (1.95-7.9 wt.%) reflecting alkaline composition of the samples. Compatible elements such as Ni (2.2-213.7 ppm) and Cr (17-739 ppm) indicate highly varied amounts, as well, suggesting nearly primitive to extremely fractionated nature. In La/Sm vs. La plot, the compositional trend is consistent with fractional crystallization process. Chondrite-normalized REE patterns and primitive mantle -normalized spider diagrams are characterized by similar patterns suggesting genetic relationships of different samples. The spider diagrams display humped-shaped patterns in which the LILEs (Rb, Ba, Sr and K) and HFSEs (e.g. Th, Ta, Nb, Zr and REEs) show enrichment with increasing incompatibility and a slightly negative Nb anomaly. These patterns are consistent with typical intraplate alkaline magmatism (OIBs). REE patterns are characterized by pronounced negative slope reflecting high LREE/HREE enrichment ((La/Yb) N= 5-17). Moreover, La and Yb represent enrichment of 47-248 and 6.5-22 times chondrite abundances, respectively. Immobile trace elements (e.g. La, Y, Zr and Nb) discrimination diagrams suggest subduction unrelated within-plate mantle origin similar to OIB source. Furthermore, the mantle source nature and partial melting degrees are inferred from modeling based on incompatible element ratios (Sm/Yb vs. La/Yb plot) suggesting that parental melt derived from garnet-bearing lherzolite and partial melting of <15%. Finally, we conclude that the area located to the southern margin of Paleotethys during Late Paleozoic was a passive margin (Gondwanian affinity) and the magmatic activity was related to thermal perturbation of mantle via hot spot/plume effects in an extensional tectonic regime

Development and Experimental Study of an Automated Laser-Foil-Printing Additive Manufacturing System

Purpose: This paper aims to present the development and experimental study of a fully automated system using a novel laser additive manufacturing technology called laser foil printing (LFP), to fabricate metal parts layer by layer. The mechanical properties of parts fabricated with this novel system are compared with those of comparable methodologies to emphasize the suitability of this process. Design/methodology/approach: Test specimens and parts with different geometries were fabricated from 304L stainless steel foil using an automated LFP system. The dimensions of the fabricated parts were measured, and the mechanical properties of the test specimens were characterized in terms of mechanical strength and elongation. Findings: The properties of parts fabricated with the automated LFP system were compared with those of parts fabricated with the powder bed fusion additive manufacturing methods. The mechanical strength is higher than those of parts fabricated by the laser powder bed fusion and directed energy deposition technologies. Originality/value: To the best knowledge of authors, this is the first time a fully automated LFP system has been developed and the properties of its fabricated parts were compared with other additive manufacturing methods for evaluation

Methods of Automating the Laser-Foil-Printing Additive Manufacturing Process

Laser Foil Printing (LFP) is a laser-based metal Additive Manufacturing (AM) method recently developed at Missouri University of Science and Technology. This study investigates and compares two different methods of automating part fabrication for the LFP process. Specifically, the edge elevation issue due to laser cutting is investigated. Edge elevation occurs after the foil cutting operation, which is an essential step of the LFP process. Previously, mechanical polishing was done to remove the elevated edges for the fabrication of each layer. However, as mechanical polishing is very time-consuming, the current study focuses on two other methods to eliminate the elevated edges. One of them uses laser polishing to remove the elevated edges. Another method is changing the order of the fabrication steps between pattern welding and contour cutting in the LFP process. Comparisons are made to observe the differences in part quality, properties, and building time between these two methods.Mechanical Engineerin

Investigation of Mechanical Properties of Parts Fabricated with Gas- and Water-Atomized 304L Stainless Steel Powder in the Laser Powder Bed Fusion Process

The use of gas-atomized powder as the feedstock material for the Laser Powder Bed Fusion (LPBF) process is common in the Additive Manufacturing (AM) community. Although gas-atomization produces powder with high sphericity, its relatively expensive production cost is a downside for application in AM processes. Water atomization of powder may overcome this limitation due to its low-cost relative to the gas-atomization process. In this work, gas- and water-atomized 304L stainless steel powders were morphologically characterized through Scanning Electron Microscopy (SEM). The water-atomized powder had a wider particle size distribution and exhibited less sphericity. Measuring powder flowability using the Revolution Powder Analyzer (RPA) indicated that the water-atomized powder had less flowability than the gas-atomized powder. Through examining the mechanical properties of LPBF fabricated parts using tensile tests, the gas-atomized powder had significantly higher yield tensile strength and elongation than the water-atomized powder, however, their ultimate tensile strengths were not significantly different.Mechanical Engineerin

Investigation of Mechanical Properties of Parts Fabricated with Gas- and Water-Atomized 304L Stainless Steel Powder in the Laser Powder Bed Fusion Process

The use of gas-atomized powder as the feedstock material for the laser powder bed fusion (LPBF) process is common in the additive manufacturing (AM) community. Although gas-atomization produces powder with high sphericity, its relatively expensive production cost is a downside for application in AM processes. Water atomization of powder may overcome this limitation due to its low cost relative to the gas-atomization process. In this work, gas- and water-atomized 304L stainless steel powders were morphologically characterized through scanning electron microscopy (SEM). The water-atomized powder had a wider particle size distribution and exhibited less sphericity. Measuring powder flowability using the Revolution Powder Analyzer (RPA) indicated that the water-atomized powder had less flowability than the gas-atomized powder. Through examining the mechanical properties of LPBF fabricated parts using tensile tests, the gas-atomized powder had significantly higher yield tensile strength and elongation than the water-atomized powder; however, their ultimate tensile strengths were not significantly different