Additive Manufacturing: Alternative Processes (Beyond the Beam): Sintering and Novel Processes
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Additive Manufacturing Committee, TMS: Powder Materials Committee
Program Organizers: Paul Prichard, Kennametal Inc.; Matthew Dunstan, US Army Research Laboratory; Peeyush Nandwana, Oak Ridge National Laboratory; Nihan Tuncer, Desktop Metal; James Paramore, Texas A&M University
Tuesday 2:00 PM
February 25, 2020
Room: 7A
Location: San Diego Convention Ctr
Session Chair: James Paramore, US Army Research Lab
2:00 PM
Gravity Influence on Sintering of 3D-printed Components: Elisa Torresani1; Randall German1; Eugene Olevsky1; 1San Diego State University
Sintering of a powder component ideally produces homogenous shrinkage while preserving the original shape of the sintered component. However, it is well known that during real-world materials processing many factors (e.g. temperature non-uniformity, external friction forces, and gravity) influencing sintering impose inhomogeneous densification and shape distortions in the final component. These issues are also present in powder components obtained using additive manufacturing technologies (AM) such as binder jetting and ceramic stereolithography. Understanding the sintering process assisting AM and understanding the factors that influence this type of sintering is of fundamental importance for the development of modeling tools able to predict the resulting shapes and properties of the final sintered components. In the present work a finite element model is developed in order to predict the sintering behavior of 3D-printed specimens under the influence of gravitational forces. Subsequently the model results are validated trough the comparison with the experimental test outcomes.
2:20 PM
Sintering Kinetics of Particle-based Ink Extrusion 3D Printed Nickel Scaffolds: Safa Khodabakhsh1; Ashley Paz y Puente1; 1University of Cincinnati
The recent increase in utilization of powder feedstock based additive manufacturing techniques to 3D print complex structures necessitates the investigation of variations in the sintering behavior of loosely packed powders as compared to traditionally compacted powder metallurgy structures. In this study, particle-based ink extrusion, where the ink contains the material to be printed in powder form, a polymer binder, and a tri-solvent mixture, was used to print Ni and Ni-Cr metallic scaffolds. To fabricate the Ni-Cr scaffolds both mixed elemental powders and pre-alloyed powders were used in the ink to quantify the differences in sintering kinetics resulting from an additional composition-based driving force. Here we discuss the measurement of sintering kinetics of such 3D printed samples investigated using a combination of traditional metallography and X-ray tomography.
2:40 PM
Selective Sintering-based Fabrication of Fully Dense Complex Shape Parts: Geuntak Lee1; Charles Manière1; Maricruz Carrillo1; Eugene Olevsky1; Elisa Torresani1; 1San Diego State University
A novel method to fabricate fully dense ceramic complex-shape components is developed. Known additive manufacturing technologies producing complex shape components using binders, include the complex and time-consuming debinding process and render low green density products. Using the proposed combination of selective sintering and powder bed 3D printing technology, fully dense complex parts can be easily produced. The total process is composed of the following steps: 1. Fabrication of sacrificial powder mold, 2. Injection of powders or slurry to the mold, 3. Isostatic pressing of the sacrificial mold and powder assembly, and 4. Sintering. The advantage of this process regarding sinterability, grain size, process time, microstructure and industrial opportunity is discussed.
3:00 PM
Development and Validation of Sub-scale Tensile Tests for Characterization of Additively Manufactured Metals: Laura Moody1; Ion Powell1; Daniel Lewis2; Brady Butler1; Ankit Srivastava2; Lara Draelos2; James Paramore1; 1United States Army Research Laboratory; 2Texas A&M University
Anisotropy, coarse microstructure, and large porosity are common problems in additive manufacturing (AM) of metals. Non-beam approaches can both simplify the manufacturing processes and produce more reliable microstructures, though verification of improved properties is still necessary. Using sub-scale sized tensile bars to test mechanical properties like strength and ductility enables characterization of AM metals at a variety of locations and orientations within a single component. Additionally, data can be gained from relatively small amounts of material. The goal of this study is to develop and validate sub-scale tensile tests that utilize a truly representative volume element in order to accurately characterize mechanical properties, thereby enabling further development and validation of metal AM processes. The effects of surface finish, size and morphology of the microstructure, and the reliability of measuring small specimen dimensions will be discussed. Additionally, data gained from sub-scale testing of non-beam AM components will be presented.
3:20 PM
Experimental Demonstration of Additive Manufacturing and Assembly in Space by Thermal Vacuum Testing: Derek Thomas1; Paul Shestople1; Michael Snyder1; 1Made In Space, Inc.
Satellite and space vehicle designs are constrained by launch vehicle shroud size and surviving launch and ascent. Astronaut assisted manufacturing and assembly has limited construction of large space-based structures due to the risks involved. Extending on the successful deployment of commercial additive manufacturing devices on the International Space Station, Made In Space, Inc., (MIS) is developing of a suite of technologies for on-orbit autonomous manufacturing and assembly as part of the Archinaut Technology Development Project. Robotic assembly and additive manufacturing (AM) have been demonstrated under simulated Low Earth Orbit environmental conditions with a thermal vacuum chamber and cyclic temperature profile. The resulting melt-extrusion produced samples provide insight into the effects of harsh environmental conditions on additively manufactured materials. The resulting properties of 3D printed bulk and thin-walled specimens provide insight to guide manufacturing process development under the harsh environments of space.
3:40 PM Break
4:00 PM
Novel Method in Additive Manufacturing of Metal Matrix Composites Reinforced by Carbon Particles: Mahdi Yoozbashizadeh1; 1California State Univ Long Beach
Several Additive Manufacturing (AM) processes have been developed in order to fabricate Metal Matrix Composites (MMCs). Most of these processes use carbon fibers or carbon nanotubes to mix with metal powder in order to be used in an existing AM process. Commercial applications of the existing processes are very limited due to: 1) Difficulties of mixing and, 2) Dispersion and distribution of carbon particles in the metal. This paper introduces a novel AM method for fabrication of metal-carbon by Thermal Decomposition of sugar. In this method sugar/sucrose are printed on metal powder bed to fabricate green part. The green part undergoes bulk sintering. During bulk sintering the printed sucrose is decomposed to carbon particles to form MMC reinforced by carbon. In order to further study the process X-ray Difraction (XRD), Scanning Electron Microscopy (SEM), and Energy-Dispersive X-ray Spectroscopy (EDS) techniques were used to analyze the fabricated bronze-carbon samples.
4:20 PM
Additive Manufacturing of Photocatalytic Materials for Solar Water Disinfection: Andrey Vyatskikh1; Kai Liu1; Carlos Portela1; Akira Kudo1; Stephane Delalande2; Michael Hoffmann1; Julia Greer1; 1California Institute of Technology; 2PSA Group
Photocatalytic materials, such as titanium dioxide (titania, TiO2), can harvest sunlight to promote generation of reactive oxygen species (ROS) that damage and deactivate waterborne pathogens. Here, we study the effects of 3D architecture of photocatalytic materials on the efficiency of solar water treatment. We have developed a stereolithography-based additive manufacturing (AM) process for TiO2. We synthesize pre-ceramic photoresists using hybrid organic-inorganic materials, pattern them using a stereolithography apparatus, and pyrolyze them in air at 1300C to remove the organic content. We demonstrate this process by fabricating periodic cubic and octet architectures with beam diameters of 115-170 um and unit cells of 0.65-1.14 mm. The resulting structures are comprised of >99wt% rutile TiO2, as confirmed by Energy-Dispersive Spectroscopy, Raman spectroscopy, and Transmission Electron Microscopy. This titania AM process offers a promising pathway to creating safe and efficient photocatalytic reactors for household water disinfection.
4:40 PM
Portland 3D Printing of Portland Cement Pastes with Additions of Kaolin, Superplastificant, and Calcium Carbonate: Luis Vergara1; Henry Colorado1; 1Universidad de Antioquia
The main goal on this investigation is to develop inexpensive formulations of Portland cement pastes for additive manufacturing using the direct ink writing technique. Kaolin, superplastificant based on cellulose, and calcium carbonate additions were all used as additives and modifiiers of the printing quality. A total of 15 formulations were built, from which 3 were able to be used in the printing process when considering the shape stability and finishing of the printing parts. Cylindrical samples of 17mm in diameter and 26mm of height were built in order to be tested in compression tests. The microstructure was characterized with scanning electron microscopy and X-ray diffraction. Mass flow through the nozzle, density, and Weibull distribution graphs were also obtained. Results showed one formulation to be the best one, which was associated mainly to an optimal kaolin content as rheology regulator.
5:00 PM
Beyond the Powder-bed: Fabricating Microscale Three-dimensional Metallic Structures Without Support Using Nanoparticle 3D Printing: Mohammad Sadeq Saleh1; Rahul Panat1; 1Carnegie Mellon University
Three-dimensional microscale metallic structures are needed in several applications such as sensing, bioelectronics, and energy storage. The established additive manufacturing methods for can fabricate structures larger than about a millimeter in feature size. In this research, we develop an aerosol-jet based nanoprinting method that can fabricate complex 3D structures without any support materials. The process is based upon dynamics of aerosol droplet condensation and evaporation. A theoretical model predicting the structure formation is developed and verified via experiments. The printing process is followed by sintering of the nanoparticles that creates near-fully dense truss segments of the structures. Highly intricate 3-D micro-lattices, pillars, and spirals are fabricated. The mechanical properties of the structures are measured. It is observed that the response of the structure to mechanical deformation can be modulated by varying the sintering conditions. Various applications of the structures made by this method are discussed.
5:20 PM
Powder Casting: Producing Bulk Metal Components from Powder without Compaction: James Paramore1; Matthew Dunstan1; Brady Butler1; 1U.S. Army Research Laboratory
Many non-beam additive manufacturing (AM) processes can be used to create metal green parts for subsequent sintering. However, the green parts often have very low relative densities, complicating sintering. For example, extrusion-based AM processes have been adapted to produce green parts using a polymer binder. However, achieving suitable mechanical and rheological properties of the feedstock often requires metal powder fractions of 50 vol% or less. Additionally, unless relatively expensive powders with excellent flowability and packing characteristics are used, binder jetting also produces parts with poor green densities. In this talk, a process called “Powder Casting” will be discussed. This process was originally developed to produce nearly fully dense metal components from loose powder by using hydrogen-assisted sintering to significantly improve densification. Results from different alloy systems and the incorporation of this method into non-beam AM processes to improve densification and, therefore, mechanical properties will be presented.