2023 Annual International Solid Freeform Fabrication Symposium (SFF Symp 2023): Materials: Metals-Novel AM Methods I
Program Organizers: Joseph Beaman, University of Texas at Austin

Wednesday 8:00 AM
August 16, 2023
Room: 415 AB
Location: Hilton Austin

Session Chair: Aaron Liao, University of Texas at Austin

8:00 AM
Formation of Easy-to-Remove Support Structures in Metal LPBF with En-situ Powder Bed Doping.: McKay Sperry¹; David Carter¹; Nathan Crane¹; Tracy Nelson¹; ¹Brigham Young University
    Laser Powder Bed Fusion (LPBF) is a popular Additive Manufacturing (AM) technique used commonly for metals. Metal parts formed by LPBF generally require supports connecting the part to the print bed to hold up the structure, remove heat, and reduce residual stresses. Because of these supports, finished parts must be cut away from the build plate, and generally require additional machining to achieve the desired geometry. In this study, a carbon suspension was deposited in the 316L stainless steel powder bed at the interface between the support and the finished part. This helped the finished part to break free from the supports without any need for machining, simplifying post-processing. The added carbon reduced the corrosion resistance of the 316L, allowing excellent heat transfer and mechanical support during printing, but causing the modified supports to etch preferentially in an electrolyte bath and release the part.

8:20 AM  Cancelled
Reduced Silver Consumption using Particle-free Reactive Silver Inks for Low-temperature Solar Cell Metallization: Steven DiGregorio¹; Michael Martinez-Szewczvk²; Subbarao Raikar¹; Mariana Bertoni²; Owen Hildreth¹; ¹Colorado School of Mines; ²Arizona State University, Ira A. Fulton Schools of Engineering
    Particle-free reactive metal inks are an alternative conductive ink technology to nanoparticle metal inks for printed electronics. Reactive inks offer simpler synthesis, greater ink stability, and, most importantly, lower processing temperatures than particle-based inks. These low-processing temperatures enable printed electronics on thermally sensitive substrates, such as silicon heterojunction (SHJ) solar cells. This work investigates how ink heat treatment, formula, and printing parameters impact the electrical properties of reactive silver inks, emphasizing the properties pertinent to solar cell metallization. 4-point resistance measurements and top-down and cross-section microscopy characterized the printed silver fingers, and IV measurements characterized the photovoltaic performance. The best-performing ink achieved silver fingers with resistivities of 3.1 µΩ·cm and contact resistivities of 3.2 mΩ·cm2 when printed at 61 °C. This ink metallized a full-sized SHJ cell and consumed 90% less silver compared to standard metallization processes.

8:40 AM
Solid-state Production of Uniform Metal Powders for Additive Manufacturing by Ultrasonic Vibration Machining: Yaoke Wang¹; Malachi Landis¹; Ping Guo¹; ¹Northwestern University
    This work presents a new technique to generate uniform and micron-sized metal powders for advanced additive manufacturing. By collecting discrete chips resulting from ultrasonic vibration machining, we demonstrate the feasibility of generating consistent powders with tight dimensional tolerance, the ability to control powder geometry, and good efficiency. It offers a new route for sustainable and low-cost manufacturing of high-quality metal powders. The powder generation mechanism is analyzed with a special tool path design to ensure consistent dimensions over multiple cuts. Aluminum and brass powders with critical dimensions of 25 by 50 µm are demonstrated and verified with selective laser melting.

9:00 AM  Cancelled
Surface Roughness of Machined 316L Stainless Steel Fabricated by FDM/ FFF 3D Printing Technology: Suleiman Obeidat¹; Eduardo Rodriguez¹; Iftekhar Basith¹; ¹Sam Houston State University
    We investigate the effect of the raster angle and the building direction on the surface roughness after milling 316L stainless steel parts printed using FDM/FFF technology. BASF Ultrafuse 316L metal 3D printing filament of 1.75 mm diameter will be used. Samples of 316L stainless steel are printed using Method X 3D printer made by Makerbot with the capability of printing parts using filaments of metal particles embedded in resin. The parts are printed at different raster angles that include 0˚, 30 ˚, 45˚, and 90˚ in two different building directions (flat and on the edge). The printed parts are sintered in a pipe furnace to obtain pure stainless-steel samples. The milling operation is performed in different directions with respect to the raster angle then we will measure the surface roughness and correlate it with the raster angle.

9:20 AM
Amorphous Magnetic Alloys Printed from Carbonyl Based Metal-organic Decomposition Inks: Collin Miller¹; Owen Hildreth¹; ¹Colorado School of Mines
    Amorphous metals are exciting because the lack of crystal structure gives them interesting and unique physical, electric, and magnetic properties. One major drawback to these materials is how difficult they are to manufacture. They often require very large temperature gradients that cause fast cooling rates in order to kinetically freeze them. This work demonstrates the ability to electrohydrodynamically print amorphous soft magnetic alloy materials using a reactive ink precursor without rapid cooling. This is possible because they are formed through a chemical reaction rather than a melt. Particle-free Iron – Cobalt reactive inks were made by dissolving organometallic metal carbonyls, such as Iron Pentacarbonyl and Cobalt Octacarbonyl, in organic solvents. These inks can be printed in an inert atmosphere using electrohydrodynamic printing then thermally decomposed into their metallic state using a heated bed at temperatures below 300 °C.

9:40 AM Break

10:10 AM
Binder Evaporation During Powder Sheet Additive Manufacturing: Joerg Volpp¹; Wenyou Zhang²; William Abbott²; Asli Coban²; Riccardo Casati³; Ramesh Padamati²; Rocco Lupoi²; Silvia Marola³; Sean McConnell²; ¹Luleå University of Technology; ²Trinity College Dublin; ³Politecnico di Milano
    Several Additive Manufacturing methods are well established and found access into regular production in multiple sectors. For processing metals, typically wire or powder is used as feedstock. For additive processes very fine powder is used. Such fine powders can be a health risk for humans (aspiration, skin integration). Therefore, an alternative process was developed that provides the powder not as free powder particles but in form of powder sheets. For enabling the necessary bonding between the particles, a binder is used. In order to understand the impact of the binder during laser processing of the powder sheets, single pulse and line treatments were produced and recorded with high-speed imaging. Recordings show the vaporization of the binder and the related ejections of powder particles. At lower energy input, the binder evaporation led to less spattering, which indicates that a binder heating at low heating rates induces less pressure on the particles.

10:30 AM
Embedding of Luminescent Pigments within 316L Stainless Steel Matrix by Laser Powder Bed Fusion for Optical Functionalities: Christina Baslari¹; Hicham Maskrot¹; Wilfried Pacquentin¹; Sonia De Sousa Nobre²; Daniel Zambon³; Rachid Mahiou³; ¹Université Paris-Saclay, CEA; ²Université Grenoble Alpes, CEA; ³Université Clermont Auvergne
    Corrosion-related degradation of metallic components presents economic, safety and environmental issues in high-tech industries. In a circular economy approach, it would be relevant to propose new eco-designed solutions for extending the service life of metallic parts. The proposed method consists in incorporating luminescent particles into metallic parts by additive manufacturing in order to track their corrosion rate, using photoluminescence to monitor the materials degradation. In this study, laser powder bed fusion was used to successfully incorporate for the first time Ce3+ doped yttrium aluminum garnet (YAG:Ce) into a 316L stainless steel matrix by controlling the influence of process parameters. Chemical compositions and microstructural changes related to phosphors incorporation have been observed by energy dispersive spectroscopy (EDS) and backscatter diffraction (EBSD) respectively. Laser induced photoluminescence spectra of embedded particles revealed new optical features. Finally, preliminary tests in nitric environment have been carried out to monitor the corrosion rate of 316L.

10:50 AM
Embedding Temperature Sensors with the Use of Laser-Foil-Printing Additive Manufacturing: Tunay Turk¹; Maxwell Dougan¹; Logan Hendrix¹; Aaron Reed¹; Cesar Dominguez²; Austin Sutton²; Jonghyun Park¹; Ming Leu¹; ¹Missouri University of Science and Technology; ²Los Alamos National Laboratory
    Laser foil printing (LFP) is a metal additive manufacturing (AM) process using laser-based melting of metal foil technique. Using metal foils in AM has advantages over common laser powder-feed processes, allowing for efficient heat transfer and resolving the drawbacks of powder-based AM, such as potential powder inhalation health hazards, balling, spattering, and high powder costs. In this study, we demonstrate the advantage of LFP for embedding sensors into structures using 304L stainless-steel foil as the feed material and two different types of temperature sensors. The first type is a resistance temperature detector (RTD) platinum sensor (Pt 100), and the second type is a k-type thermocouple probe. A detailed study of the sensor embedment through LFP revealed that laser power, dwelling duration, and scanning strategy significantly affect product quality. As a result of this study, we demonstrated the feasibility of fabricating functional parts with embedded sensors using the LFP process.

11:10 AM
Novel Welding Strategies in High Deposition Rate Laser-Assisted Double-Wire Welding Process with Nontransferred Arc: Kai Biester¹; Nick Schwarz¹; Jörg Hermsdorf¹; Stefan Kaierle¹; ¹Laser Zentrum Hannover e.V.
    Laser-assisted double wire welding with non-transferred arc melts the material using an arc between two conveyed wires. Driven by gravity the molten metal drops onto the substrate. A laser beam is oscillated on the melt pool to bond the weld beads to the substrate without undercuts. Claddings at high deposition rates (11.64kg/h) were performed with 316L on mild steel. The first welding strategy (AAA) is to weld adjacent beads (A) with a varied track spacing of 7 to 9mm. The second strategy (ABA) consists of beads (A) welded at a distance of 14 to 18mm from each other, so that a third bead (B) can be deposited in the space between. Claddings with the determined track spacing for AAA of 9mm and ABA 18mm were created in order to compare the resulting surface properties. The ABA cladding achieved a more uniform surface and less waviness than the AAA cladding.

11:30 AM
A Novel Coating Method Used to Enable Multilayer Structures with Microscale Selective Laser Sintering: Aaron Liao¹; Dipankar Behera¹; Michael Cullinan¹; ¹The University of Texas at Austin
    The microscale selective laser sintering process (µSLS) is an additive manufacturing technique that enables the creation of metal features with sub-5 µm in-plane resolution. In this process, a layer of metal nanoparticle ink is deposited onto a substrate and positioned beneath an optical subsystem with a nanopositioning stage. Using a digital micromirror device, a laser is spatially modulated to selectively heat up particles in desired regions to cause sintering. The substrate is then moved to a coating station where a new layer of nanoparticle ink is applied atop the sintered features. Initially, the slot-die coating process was adopted as the recoating method for this technique. However, due to challenges with depositing consistent ink thickness across the recoated part and limitations with the minimum layer thickness achievable, a new approach inspired by blade coating has been developed to achieve layer thicknesses of less than 1 µm.