PowderMet AMPM Tungsten Special Interest
SESSION P07 Innovative Process PM
125 - Artificial Intelligence Applied to the Development and Characterization of PM Components
Simon Gelinas, Laval University
Complexity is inherent to powder metallurgy: from microstructure that is more than often a combination of multiple constituents to alloy design where complex interactions exists and final properties that vary according to an entanglement of chemistries, processing and design parameters. On the other hand, new developments and democratization of artificial intelligence (AI) emerging from other fields are now providing new sets of tools to the PM research and development community to tackle these challenges. Amongst many things, AI can be used to automatized previously tedious tasks, such as quantitative analysis of micrographs, opening way to a larger scale understanding of the relationship between microstructure, fracture behavior and strength. The usefulness of machine learning (ML) may also be applied to alloy development and optimization through adaptative DOE and non-traditional approaches to data analysis and modeling. This work presents an overview of AI approaches that we successfully applied in PM research and where the AI results can be validated and interpreted by a human expert.
173 - Material Preparation of High-Temperature Solid-Oxide Fuel Cell Interconnector
Wei Wei Yan, NBTM New Materials Group Co., LTD
Using press-sinter method, Ni and Mo doped Cr-5Fe-1Y2O3 solid oxide fuel cell (SOFC) interconnector materials are prepared. The influence of alloy elements on sintering is studied with XRD, SEM and EDS, dilatometer, 4-point resistance test, air tight test and cell stack experiments, to explore coefficient of thermal expansion (CTE), electrical conductivity, air tightness and its improving method. At 800 °C, CTE is close to 10x10-6 K-1. Between 500-800 °C, the difference of CTE is below 1x10-6 K-1 compared to YSZ, which causes low thermal mismatch and stress. Increasing density improves electrical conductivity. When the density is 6.45 g/cm3, electrical conductivity reaches 3.081x106 S•m-1 at 800 °C. Carbonization and oxidation can improve the air tightness, because of the hair like layer structure grown on the pore wall during treatment. Cell stack experiments show good air tightness and electrical conductivity after the treatment.
128-R - Advancements in Continuous Processing of Soft Magnetic Components
Stephen Feldbauer, Abbott Furnace Company
With the electrification of our world ever growing, the application of soft magnetic components is rapidly increasing. A novel new approach was developed to produce soft magnetics in a continuous process that is more efficient and cost effective. Here the process along with the underlying science will be reviewed explaining why these developments are such an important innovation for the powder metal industry.
SESSION P08 Process Optimization and Productivity Improvement II
045 - Optimizing Sintering Furnace Design and Operating Parameters for Best Results
Ravindra Kumar Malhotra, Malhotra Engineers
Sintering furnaces are designed to achieve good control on sintered parts. However different parts of a sintering furnace are designed in many different ways. These play a role in defining sintering process parameters. One of the important sintering parameters is temperature of each zone of furnace. Along with temperature time spent by parts in each zone helps in capturing a part of the sintering process. Belt speed determines the progressive time and temperature conditions material will go through. Load on belt will determine the throughput of sintering furnace. The desired throughputs will be achieved if furnace heating system is able to support each set zone temperatures as well as temperature inside the muffle within allowable tolerance. Different heating methods have advantages or disadvantages when seen in light of above requirement. The choice of heaters is temperature dependent, but the effect of choice made is permanently carried by the parts producer as recurring cost of running as well as quality of parts produced. Sintering furnaces are energy intensive equipment in a PM plant. So, a careful study of belt loading, weight of fixtures and heat taken away by belt will help in optimizing performance of a sintering furnace. So operating parameters will influence best results from a sintering furnace.
228 - On the Propensity of Adhesion of Powders to the Tools after Compaction and Ejection
Henrietta Tsosie, Drexel University
Adhesion of powder during cold compaction is a common problem in pharmaceutical tableting but its implications have also been discussed in powdered metals and ceramics in such industries as alkaline batteries and granular production. In this work we address issues related to surface preparation and the propensity of these tool surfaces to adhere to powders after compaction. A systematic cleaning procedure that includes material removal, and sonication in a metal cleanser solution and deionized water was developed to produce a controlled state for a tool steel (S7) compaction punch used to press several pharmaceutical powders. The amount of residual powder on the surface of the punch was evaluated with a laser reflection sensor, punch tip weighing and scanning electron microscopy. Contact angle measurements of the punch surface were also completed. A number of pharmaceutical excipients were tested and ranked. Our results show that sticking is highly dependent on the state of the punch surface.
076 - Increased Productivity and Longer Tool Life in Machining High Strength Powder-Forged Connecting Rods
Bo Hu, North American Höganäs Co.
Powder-forged connecting rods for automotive applications require significant machining with multiple operations to provide precise dimensions and surface finish. Powder-forged connecting rods are commonly manufactured from copper steels with a conventional machining additive such as MnS. Recent developments in advanced machining enhancers showed the capability of advanced machining additives in improving machining for various as-sintered steels. Feasibility assessment in laboratory tests with powder-forged pucks indicated that the advanced machining enhancers have potential in improving the machining of powder-forged materials and achieving higher productivity. In this study, mass-production machining trials with actual connecting rods were performed in order to validate the performance of the advanced machining enhancer in improving the machining of high strength powder-forged materials. The results obtained from the production trials demonstrated the advanced machining enhancer could provide increased productivity by reducing the total machining cycle time 20 seconds. This was achieved in conjunction with a 100% increase in the tool life of the crank boring operation.
NEW SESSION 01 AM Materials II
230 - Impact of Atomization Gas on Characteristics of Austenitic Stainless Steel Powder Feedstocks for Additive Manufacturing
Mingze Gao, The Pennsylvania State University-University Park
Two nitrogen atomized and one argon atomized 316L austenitic stainless steel powders with similar size distributions were characterized using traditional powder characterization tools and rotating drum and annular shear rheological tools. While the traditional characterization tools and particle size measurements did not differentiate between the powders, these rheological tools allowed connections between the particle morphologies and rheological properties and powder performance to be identified. In particular, the argon atomized powders displayed higher aspect ratios, which translate into more spherical morphologies, and improved flow, defined by lower avalanche angles, when tested in the rotating drum. On the other hand, these differences in flow properties were not captured in the corresponding basic flow and specific energy measurements made with the annular shear tools. Variations in the powder packing properties and internal powder porosity in the different powder lots decreased the powder mass and introduced increased uncertainty in the force and torque measurements.
236 - Centrifugal Atomization and Characterization of Glass Forming Alloys (Al86Ni8Y6 and Al86Ni8Y4,5La1,5)
Sasha Alejandra Cegarra Salges, Polytechnic University of Catalonia
Al-Ni-Y and Al-Ni-Y-La alloys were processed by centrifugal atomization to investigate the possibilities of formation of metallic glasses due to the high cooling rates involved in this process. Al-based metallic glasses have attracted attention of the scientific community because of the expectation to develop a high specific strength material. Centrifugal atomization variables, such as disc rotational speed, melt temperature and inert gas atmosphere, were adjusted to produce particles with sizes smaller than 150 μm. The particle size distribution, cooling rate, morphology and microstructure of the as-atomized powder were investigated. The powders were characterized by using light microscopy, SEM, XRD and DSC. The glassy powders exhibited cooling rates of the order of 104-106 K/s. Further, for the composition Al86Ni8Y4,5La1,5, metallic glass powder was obtained for particles <106 μm.
238 - Development of Spheriodization Process for Electrolytic Dendritic Iron Powders
Revati Kishor Ambekar, RWTH - Rheinisch-Westfälische Technische Hochschule Aachen University
Electrolytic powders are inherently dendritic in nature and thus resist the flow because of the irregular morphological features. This limits the application of electrolytic powders wherever flowability is the main concern. A selected size range of highly pure electrolytic iron powders (99.99% purity) with mean particle size of 325 Mesh were taken for spheriodization in a specially fabricated atmosphere controlled spheriodization apparatus to get desired powder shape and size. Powder characterization was done using scanning electron microscopy, Image analysis software for sphericity measurement, and Hall flow meter for flowability. Simulation model for analyzing forces and energy dissipation during spheriodization by using discrete element modelling. After spheriodization it was observed that there was substantial reduction in flow time to 30 seconds from no flow in initial dendritic powder and improved spherical acceptable particles to 90% was achieved. Thus, overall process for spheriodization of electrolytic iron powder has been established economically.
SESSION A07 AM Modeling I
223 - Mechanical Properties of Additively Manufactured Variable Lattices of Ti6Al4V Based on Theoretical Microstructures
Cory Groden, Washington State University, Pullman
Engineered micro- and macro-structures via additive manufacturing (AM) or 3D-Printing can create structurally varying properties in part, which is difficult via traditional manufacturing methods. Herein we have utilized powder bed fusion-based selective laser melting (SLM) to fabricate variable lattice structures of Ti6Al4V with uniquely designed unit cell configurations to alter the mechanical performance. Five different configurations were designed based on two natural crystal structures – hexagonal closed packed (HCP) and body-centered cubic (BCC). Under compressive loading, as much as 74% difference was observed in compressive strength and 71% variation in elastic modulus, with all samples having porosities in a similar range of 53 to 65%, indicating the influence of macro-lattice designs alone on mechanical properties. Failure analysis of the fracture surfaces helped with the overall understanding of how configurational effects and unit cell design influence these samples' mechanical properties. Our work highlights the ability to leverage advanced manufacturing techniques to tailor the structural performance of multifunctional components.
179 - Relationship Between Segregation and Powder Handling System Design
Mursal Ashrafi, Jenike & Johanson, Ltd
Powder uniformity is key to achieving consistent quality in manufactured parts and reliable operation in powder metallurgy (PM) processes. Maintaining a uniform blend throughout the process can be challenging if the powder handling system has not been designed to avoid segregation. Segregation in PM processes is a function of particle size distribution and physical properties of the powder as well as the type of handling equipment used. It is also a function of the entire process flowsheet. Depending on the properties and equipment design, the mechanism of segregation can be different. In this paper, primary mechanisms of segregation observed in PM processes will be discussed as well as the relationship between equipment design and segregation tendency of powders. This relationship will be illustrated by going through an example process flowsheet encompassing all general PM process steps to understand how segregation occurs at each transfer point.
081 - Multiscale Materials Modeling in the Design of Fatigue Resistant High Entropy Alloy Based Material Solutions for Metal AM
Anssi Laukkanen, VTT Technical Research Centre of Finland Inc.
Fatigue assessment of complex metallic alloys is at present still a trial and error process lacking in efficiency and accuracy. This poses challenges in terms of cost and certification of the respective metal AM solutions and in the development of novel solutions. In current work we propose a micromechanics and multiscale materials modeling driven approach to improve the efficiency of evaluating the fatigue performance of high entropy alloys and to provide a greater design space to seek improvements or new alloy compositions. The methodology is presented via use cases, where detailed microstructural models are assessed by micromechanical means which capture the multiphase microstructure and the respective elevated temperature cyclic behavior. Multiscale means, especially atomistic analysis methods, are utilized to link to features like interface character, strength and influence of local composition and lattice misfit. Practical results on computed fatigue properties demonstrate the viability and use of the approach for developing and engineering respective metal AM solutions.
SESSION A08 Light Metals & Alloys
218 - Compression Techniques in Selective Laser Sintering of Ultra-High Molecular Weight Polyethylene (UHMWPE)
Holden Stanley, University of North Carolina, Charlotte
Selective laser sintering (SLS) is an additive manufacturing (AM) technique used to create intricate, solid, and personalized parts out of a powder material. A future application of this technology is in the medical device industry for creating the bearing surfaces on implant heads using Ultra-high molecular weight polyethylene (UHMWPE). UHMWPE is a thermoplastic sought after by the medical field because of its excellent material properties. It has high wear rates, good strength, and is biologically inert. The predominant technology used to manufacture UHMWPE in a solid state is compression molding. SLS is a difficult process to apply to UWMWPE because of its high viscosity. However, applying external pressure to UHMWPE during the process promotes particle fluid flow, resulting in a more dense and high wear resistive part. Experiments will be designed to evaluate optimal AM compression techniques that create a UWMWPE part applicable in the medical field.
201 - Influence of Phase Transformations on Strength and Electrical Conductivity in Al/Ca DMMCs
Dustin Hickman, Iowa State University
Few bi-metallic metal-metal composite (MMC) materials possess intrinsic properties of high strength, high electrical conductivity, and low density. One such MMC, Al/Ca, provides this unique combination of properties through the development of a PM formed wire for power transmission. By combining analysis of microstructure, calorimetry, and high energy (synchrotron) in situ XRD, we gained insight into phase transformation kinetics resulting in formation and stabilization of the unique properties inherent in Al/Ca heavily deformed metal-metal composites (DMMCs). It was found that tensile strength can exceed 300 MPa, derived from formation of an Al/Ca monoclinic intermetallic compound (IMC) formed at the interface of Al and Ca. This interface introduces a barrier to diffusion of Al into Al/Ca IMC between 150-200C, retarding the formation of additional IMCs until 275C. Ultimately, these formation and stabilization kinetics establish that the upper operating temperature limit of Al/Ca DMMCs exceeds 200C. Funding from DOE-OE through DE-AC02-07CH11358.
113 - Microstructure and Mechanical Properties of Al-Cu-Mg-Ag-Ti-B Processed by Laser Powder Bed Fusion: Effect of Heat Treatment
Philipp Mair, University of Innsbruck
This study describes the effect of a T6 heat treatment on the microstructure and tensile properties of an A205 alloy (Al-Cu-Ag-Mg-Ti-B) processed by laser powder bed fusion (LPBF) and compares it to the as-built condition. With the T6 heat treatment, the grain size of the equiaxed α-Al grains increases from 0.64 ± 0.26 μm to 1.82 ± 1.21 μm. The θ-Al2Cu equilibrium phase, which is present at the grain boundaries in the as-built condition, is completely dissolved during the solution heat treatment. During the aging heat treatment, nano-sized tetragonal θ' and orthorhombic Ω transition phases are precipitated within the α-Al phase. These precipitates show a coherent interface to the α-Al phase and contribute to improving the strength. The yield strength of the T6 heat-treated samples is 359 ± 2 MPa, the tensile strength 451 ± 3 MPa, and the fracture strain 10.7 ± 0.7%. These excellent mechanical properties are due to the very fine-grained microstructure, together with the effective precipitation hardening of the alloy.
SESSION A09 AM Powder Characteristics III
103 - Application of Novel and Standard Test Techniques to Evaluate Powder Flow for AM
Cameron Blackwell, The Manufacturing Technology Centre
Critical to the success of the AM industry is the control of the entire AM process chain, encompassing design, AM processing, post-processing, and material supply. Although intrinsically linked, the relationship between raw material and final part properties is not yet understood. Traditional characterization techniques used to assess AM powder often lack applicability to the AM process. To validate the correlation between the powder and quality of parts, it is proposed to compare both standard and novel powder characterization techniques and correlate this with quality attributes of components manufactured using AM. This presentation is part of a three part series comparing traditional and novel tests, for the evaluation of powder flow, particulate properties and cleanliness. This presentation focuses on the effect of powder flow on part properties and includes analysis of spreadability, funnel flow, static and dynamic angle of repose, tap testing, rheology, shear cell, and triboelectric charging.
203 - Development of Novel A8 Tool Steel Powders for AM Produced by Water Atomization
William Chaîné, Laval University
The majority of additive manufacturing processes use metal powders that are produced by gas atomization as input material. Development of metal powders for AM produced by water atomization could bring significant advantages related to cost reduction. Obviously, water atomization is not appropriate for all the alloys of interest in AM but it certainly is for tool steels. This is even more the case since recent development allows the production of regular (near spherical) particles by water atomization. This study compares the mechanical properties of AM components made of A8 tool steel powders that were water atomized with those of identical specimens manufactured with powders that were water atomized and subsequently spheroidized in an inductively coupled plasma. An economical analysis evaluating the potential cost reductions brought about by these two approaches is presented.
153 - Microstructural and Micromechanical Characterization of Microparticulate Feedstock for Solid-State Cold Gas-Dynamic Spray Metal Additive Manufacturing
Bryer Sousa, Worcester Polytechnic Institute
Unlike many modern metal additive manufacturing methods, cold gas-dynamic spray metal additive manufacturing is a solid-state process. Due to cold spray’s solid-state nature, the process may be considered retentive, such that the feedstock’s material properties are refined and retained and therefore directly influence the resultant component performance. As a result, metal additive manufacturing via cold spray processing enables a unique degree of freedom wherein feedstock powder can be pre-processed via chemical, thermal and/or mechanical means to yield powder properties that achieve finely tuned consolidations with application-specific behaviors. With the aforementioned in mind, the present work is concerned with the through-process integration of mechanically and microstructurally evaluated microparticulate feedstocks for tunable and optimizable cold spray metal additive manufacturing. Accordingly, nanoindentation (dynamic, static and quasi-static) was coupled with numerable microstructural evaluation modalities for experimental purposes during feedstock evaluation, testing and characterization. As for the material systems considered herein, atomized aluminum alloys, atomized stainless-steel and copper feedstocks, among others, were studied. Consequently, the present work substantiated the way in which controllable component performance and properties can be achieved via proper microparticle feedstock pre-processing and/or characterization prior to use in cold spray metal additive manufacturing.
SESSION T03 Molybdenum—AM Processing
207 - Real-Time Process Monitoring for Multivariate Statistical Process Control in Powder Bed Fusion Metal Additive Manufacturing
Venkatavaradan Sunderarajan, Georgia Institute of Technology
The application of Multivariate Statistical Process Control (MSPC) to optimize Powder bed Fusion (PBF) metal Additive Manufacturing (AM) process parameters, as well as to continuously track and adjust them is presently at a low level of maturity. The ability to implement MSPC will ubiquitously bolster industry sectors where PBF metal AM adoption is currently hindered by the absence of a reliable framework for quality control. It is critical to establish reliable relationships between the AM process parameters and the process/part characteristics. Herein, the instrumentation used to facilitate real-time process monitoring for this purpose shall be demonstrated. Various instruments, their specific characteristics, the corresponding process information gathered as well as the data generation relevant to capturing the real-time physics of the process will be comprehensively detailed. This will enable us to validate currently known relationships between process variables and part quality metrics and to elucidate hitherto obscure and potentially complex ones.
050 - Process Parameter Development and Characterization for Additive Manufacturing of Molybdenum-Based Powders via Laser Powder Bed Fusion (LPBF)
Faith Oehlerking, H.C. Starck Solutions
Molybdenum (Mo) and its alloys are one of the refractory material groups which are of interest for AM production because of their application in aerospace and medical industries. The present research and development work aims to develop the proper parameter sets for pure Mo and its alloys, such as Mo-Re and TZM. An experimental scheme for parameter development was developed based on a factorial design of experiment for optimizing laser power, point distance, hatch distance, and exposure time. Primary parameter optimization target was maximizing the relative density of the specimens. Test specimens with relative densities of greater than 98% were successfully fabricated. Mechanical testing and microstructural characterization were conducted on the specimens, from which data was extracted for further fine tuning of the process parameter sets. Finally, a parameter file for each material was built as a part of the AM parameter library for our refractory materials.
129 - Structure Property Relationships of Refractory Metals Fabricated Using Electron Beam Powder Bed Fusion
Michael Kirka, Oak Ridge National Laboratory
Refractory materials are highly sought after in high temperature applications due to their high melting point. However, manufacturability of these materials, in particular casting, is hindered by this very same characteristic. Electron beam melting additive manufacturing offers a novel processing route for producing components from refractory metals. Despite their high melting point the electron beam process is well suited for selective melting and in addition can heat the entire powder bed thereby mitigating against cracking. In this talk we present our work on the processing of pure molybdenum via electron beam melting additive manufacturing. We show that fully dense and defect free material can be obtained with desirable mechanical properties. We find that the mechanical behavior of the fabricated material is sensitive to the underlying microstructure which is inherited from the imposed AM process conditions.
Special Interest Program Abstracts
SIP 1-3 Improvement in Precision / Accuracy / Variation Control II: Equipment Advances
562 - Thermal Processing Improvements to Reduce Variation in PM
Dustin Yetzer, Abbott Furnace Company
Today’s PM part manufacturers need to find new and innovative ways to remain competitive against other technologies and require ways to reduce variation in their manufacturing facilities. This review of how current solutions like improved de-lubrication to advanced cooling systems can help reduce variation in the PM manufacturing process. It will also review how todays connected controls systems can help identify potential quality issues before they become serious and thus reduce part cost and add a competitive edge for dealing with today’s challenges.
555 - Improvement of Dimensional Precision in PM Steel Parts
Cody Kalinoski, Engineered Sintered Components
Lack of dimensional precision in powder metal parts prevents the cost effectiveness of the technology’s utilization in many demanding applications in which strict tolerances are required. In some cases, machining or sizing cannot be avoided, but even in such cases, dimensional control of raw parts is the key to controlling the dimensional precision of the finished product.
Case studies involving an actual high precision production part will investigate the effects of the following on dimensional precision of in-process and finished parts.
a) Powder (type of additive)
b) Compacting (weight, density)
c) Sintering (temperature, belt speed)
546 - 3D Printing for Production: Reducing Variation of Binder Jet 3D Printed Parts
Andrew Klein, ExOne
Among the metal 3D printing technologies, binder jetting is becoming recognized as the technology with the best value proposition to produce production quantities of parts. The low cost of powders, high speed of printers and ability to leverage industry standard furnaces all make the printing process attractive for production applications. One of the challenges associated with the binder jet process is that fine, cohesive powders need to be spread into thin layers across a wide powder bed. Any variation in green density that occurs during the spreading and printing process will cause variability in final part tolerances from the sintering furnace. This presentation will discuss the methods and techniques used on binder jet 3D printers to minimize variation and improve the sintered part accuracy of parts produced using binder jet 3D printing.