PowderMet          AMPM          Special Interest

916 - Microstructural Characterization of Laser Powder Directed Energy Deposition (LP-DED) Niobium Alloy C103
Brandon Colón, University of Texas at El Paso

Laser Powder Directed Energy Deposition (LP-DED) allows for larger builds compared to Laser Powder Bed Fusion (L-PBF) systems. Recent development efforts by NASA, academia, and industry partners have focused on maturing the use of Niobium-based refractory alloy C103 due to its stability of mechanical properties under high temperatures. This work focuses on the parameter development required to fabricate aerospace propulsion C103 components using LP-DED. A Design of Experiments was performed to identify process parameters that produced thin wall specimens with the highest density and acceptable resolutions. Quantifiable microstructural characterization including melt pool dimensions, porosity, and other features was conducted for the selected specimen. Physical characterization including measurements of surface texture, thickness, and geometrical accuracy is also reported and discussed.

067 - Bioinspired Piezoelectric Composite Material with Antibacterial Effect
Joao Pinto, University of Minho

Bacterial resistance is becoming more widespread due to healthcare and agriculture antibiotics’ excessive use. Current solutions are focused on preventing biofilm formation with chemical surface coatings (antibiotics) that kill the bacteria once they arrive on the surface. This approach makes bacteria even more multi-drug resistant. Additionally, the use of contaminated shoe-soles can impart microbial dissemination in controlled atmosphere of healthcare and food industries. This work proposes design, fabrication, and characterization of a bio-inspired material with active antibacterial surface through piezoelectric surface potentials for medical and footwear applications. Barium titanate (BaTiO3) is a lead-free piezoelectric (191pC/N) bioceramic without toxicological risk. BaTiO3 presents a direct piezoelectric effect as a response to deformation. Surface potentials are directly related to bacterial adhesion inhibition and bacterial rupture through cell membrane penetration and disruption. In this sense, composites with BaTiO3 particles and Polyether-Ether-Ketone (PEEK) were produced at different percentages. The composites were mixed, and hot pressed to produce samples for characterization through wettability, SEM, and XRD analysis, along with bacterial adhesion with Gram-positive (Staphylococcus Aureus) and Gram-negative (Pseudomonas Aeruginosa and Escherichia coli) bacteria. Antibacterial properties of the functional surface are majorly dependent on material composition (percentages and phases) and process parameters (pressure and temperature).

044 - A Nature-Inspired Superhydrophilic Nano-Powder Based Silicone Rubber Composite 
Vipin Richhariya, University of Minho

Silicone-Rubber (SR) is an elastomer prominently used in biomedical and medical devices, implants, and winter shoe industries because of its stability, durability, friction properties, biocompatibility, anti-bacterial, temperature resistance, and hypoallergenic characteristics. However, inherent hydrophobicity limits the use of SR as it cannot form a protective liquid layer for implants and medical devices while placed internally or externally and impairs tissue adhesion as well. Moreover, hydrophobicity reduces ice adhesion strength in the absence of capillary bridges and that makes winter shoe-soles more slippery. The physical and chemical solutions like oxidation, UV, plasma, corona discharge, gamma radiation, and Laser radiation grafting to turn SR into hydrophilic are either temporary or change the bulk properties of the compounds. We propose an innovative multifunctional SR composite incorporating zirconia and/or titania nanoparticles produced by roller mixing followed by hot compression moulding (pressure/heating vulcanisation). Subsequently, nature-inspired patterns like gecko or frog toepads are produced on SR compound by Laser-Surface-Texturing (LST) to expose the nanoparticles that attract water molecules. A parametric optimisation along with nanopowder percentage decides the wettability of the composite. A permanent superhydrophilic SR compound was produced that can be further used to increase ice adhesion to manufacture anti-slipping winter shoe-soles or other biomedical applications. 

084 - Properties of Green and Sintered FC-0208 Using HGS 2.0
Cole Bressler, Penn State University, DuBois

The lubricant in powdered metal plays an important role in the powdered metal process. It allows parts to be ejected from the die during molding, as well as hold the part together before sintering. With the use of better lubricants, time and money can be saved in the powdered metal industry due to the improved properties. Improved green strength and lower ejection forces means less broken green parts as well as the ability to machine green parts, reducing the wear on tooling. With the use of High Green Strength Second Edition (HGS 2.0) lubricant these desired properties could be achieved. A new proprietary lubricant, HGS 2.0, is being tested to determine its properties when used in the powdered metal process. This research is presenting the properties of HGS 2.0 lubricant as well as green and sintered parts of FC-0208 blended with this new lubricant.

072 - Advanced Rheological Investigation of Lubricant Particle Size on Powder Properties of Metal Powder Mixtures Using FT4 and Granutools
Amir Shirani

Properties of powder metallurgy (PM) premixes (metal powder with alloying ingredients and lubricant) are influenced by PM lubricants. The chemistry, particle size, shape, and crystalline structure of the lubricant affect its performance in the premix. Ethylene-bis- stearamide (EBS) is one of the conventional ingredients commonly used in PM lubricants. In this investigation, the rheological characteristics of iron-based premixes, with various particle sizes of EBS but the same crystalline phases and particle shape, were investigated using the FT4 Powder Rheometer® and Granutools™ instruments. The powder flowability of conditioned and consolidated powder was examined in FT4 and compared with the cohesion index obtained as a function of rotating speed in Granudrum™. The density evolution of powder and powder compaction kinetics were classified in the FT4 compressibility program and Granupack™ tools, respectively. This work confirmed that the larger lubricant particle size and lower amount of graphite resulted in faster powder flow. However, the apparent density and kinetic of packaging were adversely affected by the larger size of lubricant in the premix. 

942 - Adhesion of Powder onto Tools During Compaction
David Freiberg, Drexel University

During compaction of powder into tablets, the phenomenon known as "sticking", where particles from a powder compact adhere to the tool punch after the punch is unloaded, is a persistent and insufficiently understood problem.  In this work, we use the Discrete Element Method (DEM) to simulate sticking via a non-continuum model for the first time.  With these simulations, we show the importance of inhomogeneity in the onset of sticking, we show that the strength of adhesion between powder and punch is not sufficient to predict sticking, and we show that two materials differing only in interparticle cohesion and powder-punch adhesion can have the same maximum tensile force and yet have opposite sticking behaviors.

190 - Effect of Powder Characteristics on Processibility in Binder Jet Metal Printing Technology (BJT)
Harsha Jamadagni, Indo-MIM Pvt. Ltd.

Powder properties play a major role in dictating printing and sintering characteristic on a component level in Binder jet metal printing technology (BJT). Particle size distribution (PSD), tap density, powder morphology and Flowability of powder are the critical properties affecting the part quality. There is lot of scope to study and understand the effect of powder properties on the component deformation and dimensional criticalities in BJT. The present research study reveals the effect of the mentioned powder properties on the above said aspects on a component level. The study may also be extended to determine the batch-to-batch variation in the powder in a production environment while manufacturing highly complex, precision components from SS 17-4PH powder in a manufacturing industry. The binder chosen in the study is the standard binder system supplied by the printer manufacturer.

087 - Control of AISI 4340 As-Printed Hardness via LPBF Parameter Selection 
Allan Rogalsky, MSAM - Univeristy of Waterloo

Water atomized (WA) low alloy steels have potential for adoption in laser powder bed fusion (LPBF) due to their high mechanical performance and relatively low cost.  For complex shapes, where LPBF provides the greatest benefit, it is beneficial if as-printed properties are as close to service requirements as possible. This study proposes a combined physics-based modeling and empirical strategy to control the as-printed hardness of WA AISI 4340 steel, while maintaining good as-printed density. A meaningful variation in part properties can be achieved using parameters such as laser spot size, power, effective velocity and hatch spacing to control heat dissipation, melt pool geometry and melt pool stitching. Control of heat dissipation was found to be particularly important if similar mechanical properties are to be achieved across a wide range of part geometries.  Hardness values achieved range from HV 364 to HV 407 while maintaining a relative density of 99.5±0.2%.

202 - ATO Atomizing Systems Manufacturing
Ashkhen Ovsepyan, Additive Plus

Additive Manufacturing (AM) is a novel manufacturing process, which requires special raw materials in the form of fine powders. The present speech is focused on developing a new method for the powder production based on ultrasonic atomization integrated with an electric arc melting. Physics-based principles of the droplet formation process for the invented device and the key features of the sub-systems are to be discussed. As an example of semi-industrial scale application of the Ultrasonic Atomization (UA), the titanium and high alloy steel powders were produced along with characterization of important technological parameters such as particle size distribution, sphericity, density, and flowability. As proven by the test campaign, the ultrasonic atomization method is capable of supplying premium quality powders without defects at high density with very good flowability. Then they can be successfully qualified as proper input for 3D printing.

159 - Additive Manufacturing Process Development DOE for NASA HR-1 Using Laser Blown Powder Directed Energy Deposition 
William Evans, NASA Marshall Space Flight Center

This investigation was focused on conducting a design of experiment program aimed at mapping the process window for NASA HR-1 using the laser blown powder directed energy deposition process. The research team at NASA Marshall Space Flight Center conducted a two phased DOE, the first phase of the experiment was focused on optimizing single bead tracks while the second phase of the experiment was focused on optimizing bead overlap in a multi pass bead build up. During the first phase of the experiment the team focused on varying primary deposition variables, namely laser power, travel speed, and powder feed rate. The second phase saw the down selection of a single bead parameter set and the team focused on varying overlap distance. In this paper the research team will outline the approach to conducting a DOE and highlight the results of the two phased experimentation approach. Results of these experiments were measured in bead geometry, as built microstructural evolution, and porosity number. The team at MSFC saw a variety of results across the process map created during the first phase of experimentation and were able to down select a parameter that created an optimal bead shape with a minimal amount of build porosity. 

030 - Investigation of Powder Electrostatics in a Laser Metal Deposition (LMD) Process
Aurelien Neveu, Granutools

Powder-based additive manufacturing of metal powders is widely used and gain more and more interest for the build of parts whose complex structure is unreachable with standard machining. Different techniques have been developed, some involve the localized fusion of particles in a powder bed, the drop of binder, or the successive deposition of fused metal to cite only a few. Whatever the technique used, the powder has to be conveyed through the different stages of the process in the printer. During the flow of the powder, the multiple contacts between the grains and with the conveyer material lead to a charge build-up inside the powder due to tribo-electric effect. Upon increasing the charge density, an electrostatic related decrease of powder performance can arise and leads to problems in processability. A better understanding of the process stages that contribute to charge build-up will allow future improvement of additive manufacturing with powder. In the present study, the electrostatic charging of a metal powder during conveying through the different parts of a Laser Metal Deposition (LMD) machine has been investigated with the GranuCharge. Powder samples are taken at different locations of the powder conveying stage to assess their respective influence on the charge build-up. We highlight the influence of the powder distributor speed on the charge build-up.

931 - Process-Microstructure-Property Relationships in Laser Powder Bed Fusion of Non- Spherical Ti-6Al-4V Powder
Mohammadreza Asherloo, Illinois Institute of Technology

An investigation of process-microstructure-property relationships in Ti-6Al-4V parts processed using laser powder bed fusion of non-spherical powder showed full control over porosity content, surface roughness, microstructure, texture, and hardness. Increasing laser scan speed from 400 mm/s to 1500 mm/s eliminated the keyhole porosities and enhanced relative density to ~99.8 %. Also, the surface roughness (Sa) decreased from 119 μm to 21.8 μm. Microstructural observations showed that the primary beta grains were refined, and their shape factor increased from ~2.5 to ~5. Additionally, the hardness reached a maximum of 390 HV 0.5 when the scan speed was 1250 mm/s. An increase in laser power from 225 W to 370 W slightly changed the Sa between 16.2 - 21.43 μm. Additionally, the hardness increased from ~355 HV 0.5 to ~383 HV0.5 with increasing laser power. Synchrotron X-ray high speed imaging also showed the direct correlation between the melt pool depth and the texture intensity.

172 - Stress-Strain Curves using a Profilometry-based Indentation Plastometry (PIP):Studies on Binder Jet (BJ) and Laser Powder Bed Fusion (PBF-L)
Animesh Bose, FAPMI, Optimus Alloys

Profilometry-based indentation plastometry (PIP) can be used to determine the stress-strain characteristics of metallic materials from indentation testing of a small, localized area. It is currently very well suited for testing on isotropic, fully-dense and homogeneous materials. The procedure uses the residual indent profile and an (accelerated) iterative FEM simulation of the indentation process. The plasticity parameters in a constitutive law (within an indentation finite element model) are repeatedly changed until optimum agreement between measured and predicted residual profile shapes is obtained. The technique characterises the full uniaxial stress-strain relationship, including the yield stress and ultimate tensile strength. 
Binder jet 3D printed parts in the as-sintered state can have residual porosity in the range of 0.5 - 2 %. This study looks at the effect of porosity on PIP testing, and shows how using novel finite element analysis this can be accounted for to allow accurate predictions of stress-strain properties for metallic materials containing porosity. 

152 - An Investigation on the Impact of Density on Electrical and Mechanical Properties of Pure Copper in Binder-Assisted, Sinter-Based Additive Manufacturing
Mahmood Shirooyeh, 3DEO, Inc.

The development of pure copper in additive manufacturing has been of great interest. The production of complex parts is more feasible using additive manufacturing technologies compared to traditional manufacturing methods. Pure copper exhibits high electrical and thermal conductivity which can be applied in heat exchangers or electronics. Achieving high-density copper requires specific material and process control in binder-assisted AM. This work presents the additive manufacturing of copper parts via Intelligent Layering with different processing leading to differences in density. Intelligent Layering is a binder-assisted, sinter-based additive manufacturing technology with subtractive elements. A variety of test coupons were manufactured and tested for their mechanical properties, or electrical conductivity. These measurements are compared to evaluate the effects and implications of differing densities on part properties.

006 - Low Temperature Synthesis of Nano-ZrB2 and LaB6 and Their Effects on Mechanical, Optical and Magnetic Properties of 17-4PH and 316L  
Arun Chattopadhyay, Uniformity Labs, Inc.

In Additive Manufacturing 316L and 17-4PH stainless steels are the most common structural materials for various applications. The effect of nano crystalline ZrB2 and LaB6 synthesized by low temperature magnesiothermic processes was studied for both austenitic 316L and martensitic 17-4PH steels. The presence of both nano-ZrB2 and nano-LaB6, singularly or in the form of a mixture, showed improvement in mechanical properties and wear resistance of the sintered parts. Near-IR spectroscopy was also carried out to detect optical changes introduced by the presence of plasmonic LaB6 nanoparticles.   

116 - Fabrication of Nearly Fully-Dense Low-Alloy Steels using Water-atomization and Binder Jetting
Mingzhang Yang, Waterloo University

Producing high-quality steel parts with high geometric fidelity, low final porosity, high surface quality, and high mechanical strength is commonly believed to require gas/plasma atomized powders with fine particle distribution. This study challenges this common notion and presents an approach to achieve these qualities using relatively coarse water-atomized powders (D90 = 71.56 µm) with oxygen content (0.18 wt.%). In this work, the experimental steel powders, modified from AISI-4340, were binder jetted and sintered using super-solidus liquid phase sintering (SLPS), resulting in a nearly fully-dense part (99.7%) with no visible distortion and low surface roughness (Sa = 3.84 µm). The resulting part can be heat-treated to comparable hardness to laser powder bed fusion or wrought AISI-4340. In addition, the experimental steel powders allowed for the successful manufacturing of micro-textured surfaces with a feature depth of 200 µm. This offers promising opportunities for achieving surface functionality in the realm of binder jetting and water atomization.

175 - Optimization of the De-Bind and Sintering Cycles of Binder Jetted 17-4 Components
Stephen L. Feldbauer, Abbott Furnace Company

Binder jetting is quickly becoming recognized as one of the most desirable methods for producing high-volume additively manufactured components and developing new printed material.  Although this technique has been available for two decades, the optimal time to de-bind and sinter components remains an area that is not well understood. Better understanding must be developed of optimal de-binding for the full advantage of this method to produce high-volume components to be realized.  

Through time stop studies, components of 17-4 material of varying thickness will be analyzed for lubricant removal and degree of sinter.  By understanding the de-binding steps as a function of time, the optimal time for de-binding and sintering as a function of the components thickness can be determined.  This information can then be used to optimize the binder jet process, advance production rates, reduce cost, and improve product quality.
 

062 - Effect of Boron on the Sintering and Mechanical Properties of Parts Made from a Steel Powder of AISI 4340 Composition Developed for Binder Jetting 
William Bouchard, Universite Laval

Contrary to additive manufacturing (AM) processes that rely on laser/electron beam melting, binder jetting (BJ) counts on sintering for the development of adequate mechanical properties. Utilization of a permanent liquid phase to promote densification at lower temperatures is an attractive strategy for BJ. This project investigated the possibility of adding boron, a well-known liquid phase promoter in PM steels, to densify components made from a water-atomized powder having the chemistry of AISI 4340 low-alloyed steel. The results obtained show that the use of a small weight fraction of pre-alloyed boron permits substantial densification to be achieved with usual sintering conditions i.e., 30 minutes at 1200 ˚C.

507 - Refractory Metal Alloys for Gas Turbine Applications – A New Age of Ultrahigh Temperature Materials
Zhigang Zak Fang, University of Utah

High-temperature materials are the pillars of modern gas turbine technologies for aerospace and electric power generation. However, the operating temperature of gas turbines is limited by the temperature capability of the metal alloys. The state-of-the-art nickel-based superalloys can operate continuously at temperatures up to 1,100 °C, which is as high as it can ever go. Recently ARPA-E of US DOE initiated a program, namely the ultra-high temperature impervious materials advancing turbine efficiency (ULTIMATE) program, to develop ultra-high temperature materials that can operate continuously at 1,300 °C. Such ultrahigh-temperature alloys will be based on refractory metals. The successful development of such ultrahigh temperatures must meet high-temperature strength, oxidation corrosion resistance, and manufacturability requirements. This is possible today by the convergence of the tremendous power of today’s computational alloy design, the vast untapped space of refractory high entropy alloys, and the unlimited potential of additive manufacturing. This presentation will discuss the scientific rationale and the synopsis of the ARPA-E ULTIMATE program. 

508 - Design and Fabrication of Refractory Mo-Si-B Alloys Using Additive Manufacturing
Dan Thoma, University of Wisconsin-Madison

Processing of ultra-high temperature refractory alloys are being explored using controlled reactive synthesis of refractory molybdenum powder with silicon nitride and boron nitride. Pre-blended mixtures of the powders were used as the feedstock during additive manufacturing. To achieve a chemically homogeneous product with minimal processing defects, a dimensional analysis was devised for process control in directed energy deposition (DED). Based on the dimensional analysis, a high-throughput design of experiments defined the optimal process window for efficiency, microstructural control and property optimization. The dimensional analysis also permits scalability to other additive manufacturing techniques, and translation to laser powder bed fusion (LPBF) was achieved. Microstructures and properties indicate refined structures with structural integrity. The results demonstrate an effective strategy to use reactive synthesis for additively manufactured Mo-Si-B alloys.  The details of the methodology and resulting properties will be highlighted.

509 - Processing of Tungsten and Tungsten Alloys through Electron Beam Additive Manufacturing for Fusion Energy Applications
Michael Kirka, Oak Ridge National Laboratory

Tungsten and its alloys are considered a robust material for the fabrication of plasma facing components due to the materials resistance to damaging plasmas and high heat-fluxes. However, the manufacturability of tungsten and its associated alloys through powder metallurgy, wrought processing, and casting is difficult and provides for little geometric complexity. Additive manufacturing techniques such as electron beam melting (EBM) offer novel processing routes for producing components from refractory metals such as tungsten. Despite the many defect mechanisms that occur in tungsten (i.e. cracking and porosity), leveraging engineered scan strategies can lead to mitigation of these defects. Here we will report on the processing science and processing observations of pure tungsten and tungsten-rhenium alloys via electron beam melting additive manufacturing. Further, the linkage between the EBM process settings and resultant as-fabricated microstructures of these materials will be discussed.