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Monday Sessions
2:00 p.m. - 3:15 p.m.

PowderMet          AMPM          Tungsten          Special Interest

PowderMet Abstracts



SESSION P04   Advanced Synthesis and Powder Processing

141 - The Influence of Particle Size Distribution on the Flowability of Ti-6Al-4V Powders for Additive Manufacturing Processes
Mahdi HabibnejadKorayem, AP&C Advanced Powders and Coatings, Inc.

The recent development of powder characterization methods has opened opportunities to determine a variety of powder properties to be related to function in specific manufacturing processes. This however has not provided enough understanding on which characterization method would determine the flow properties for additive manufacturing processes. In this study, Ti-6Al-4V powders with six particle size distributions of 15-45 um, 15-75 um, 15-90 um, 45-75 um, 45-90 um, 45-106 um were compared with respect to their surface appearances, flowability, spreadability and packing densities by using the most conventional characterization methods including Hall, Carney, FT4 and granuetools. Measurable differences were observed primarily in the above characteristics indicating the differences in the additive manufacturing processability of the powders. Moreover Ti-6Al-4V powders with various particle size distribution were characterized to collect a big data such as basic flowability, compressibility, aeration response, shear, dynamic repose angle and cohesion indices. The results were used to rank the powder flowability by means of creating a scorecard analysis to identify the interrelationship amongst the characteristics and propose what feature are the most influential properties on the powders flowability. Besides, a methodology based on computer vision, machine learning, and artificial intelligence are proposed to classify the characteristics of powders having highest flowability. 

063 - About the Complexity of Producing Spherical Metal Powders
Martin Dopler, Metalpine GmbH

A reliable quality of the metal powder is decisive for the success of additive manufacturing technologies. Powder producers struggle with a low product yield for the requested narrow particle size distributions as well as high production costs due to bad energy conversion during the atomization process. Additionally, oxides or nitrides formed during the atomization process affect powder chemistry, even more at the elevated temperatures necessary for gas atomization. This study describes the evolution of the molten alloy from the melt tundish until its transformation into metal powder. After the formation of a liquid film at the nozzle tip, the melt undergoes primary breakup into ligaments which further break down into „sausage-shaped“ fragments. Theoretical calculations of this process include the droplet formation process, the cooling/solidification process and the oxidation process. Practical results for different metal powders are compared to the calculations with regards to particle size, sphericity and surface oxides content.

237 - Development of Spheriodization Process for Electrolytic Dendritic Iron Powders
Jay Anil Runwal, 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 P05   Advanced Ferrous Pre-Mixes


058 - Improved Powder Compaction Through Use of Advanced Binders and Lubricants
Neal Kraus, Hoeganaes Corporation

Binder-treatment of premixes is extremely effective in improving part-to-part consistency, weight variation, powder flow, and overall cleanliness.  As part geometries become more complicated and faster filling speeds are desired, additional benefits of binder-treatment can be realized.  More recent studies have shown exceptional filling behavior and higher stroke rates when converting to precision bonded products.  When combined with advanced lubricants, higher densities can be achieved with lower ejection forces and excellent surface finish.

077 - Mix Solution for High Green-Strength and Green Machining
Amber Tims, PMT, North American Höganäs Co.

A new mix system that provides increased green strength has been developed. By achieving a high green strength, it is possible to reduce the formation of green cracks during part ejection and handling which provide the possibility of reducing green scrap. Another potential opportunity with high green strength is the ability to facilitate green machining. This mix system has been developed to provide high strength together with good fillability and ejection characteristics. In this study, the performance of this newly developed mix system is evaluated and compared to the common industry lubricant amide wax.  This new mix system is shown to increase the green strength by up to 60%  in a FC-0208  material system compared to premixes based on amide wax. This increase in green strength will also be shown to provide opportunity for a robust green machining solution. 

092 - Toward the Improvement of Dimensional Control in FeCuC Steels
Elena Bernardo, AMES (Spain)

Sintering in the presence of a liquid phase is still a challenging production method. This work offers a new insight into the dimensional stability of FeCuC steels through the use of Cu in the form of a master alloys (MA). The composition and melting ranges of different MAs have been tailored with optimized Mn, Si and Ni contents in order to promote liquid formation below 1120 ºC. Dimensional behavior of the Cu-based MAs is performed through dilatometry trials and compared to plain Cu when admixed to Fe powders and different C contents between 0.2 and 0.8 wt.%. A comparison of the TRS, UTS and hardness values is also here presented. The particular interest of these new designed MAs lies in a decreased Cu-swelling effect and better tolerances without endangering the mechanical properties. Both the composition of the MA and the amount of C seem to play the main role in the dimensional stability of these steels. 


SESSION P06   PM Applications


061 - Lightweighting Material and Process Options for Automotive Applications—Focus on PM Aluminum
Chaman Lall, MPP

Mobility vehicles powered by hydrocarbon fuels are subject to regulation by Federal emission standards that are aimed to reduce greenhouse gases. Because of the high number of automotive vehicles in use globally, they present the greatest threat to the environment. The automotive industry has developed strategies to improve fuel efficiency- one of those being the reduction of vehicular mass. One approach is the utilization of low-density materials such as the alloys of Al, Mg and Ti. This presentation aims to provide an overview of light weighting options using these materials, with a specific focus on the powder metallurgy (PM) technology as applied to the processing of aluminum alloys.  An new alloy developed presents an opportunity to reduce mass by 50%; this alloy has a yield strength of about 300 MPa, and a tensile elongation of about 2%.  The technical and economic feasibility of various paths to vehicular mass reduction will be reviewed.

131 - Fabrication of Titanium-Based Porous Scaffolds by Powder Metallurgy for Bone Tissue Engineering Applications 
Babak Jahani, North Dakota State University

Titanium-based porous alloys have received lots of attention for orthopedic and dental damage management. However, the ideal porous Ti alloys must be able to mimic the mechanical properties of natural bone. In this research, porous scaffolds based were fabricated from Ti35Zr28Nb by powder metallurgy.  The fabricated samples exhibited over 60% porosity as well as approximate compression yield strength of 130 MPa and elastic modulus of 3 GPa which are desired mechanical properties for material in orthopedic applications.

003 - Recent Developments on Forged Special Steels, Remelting and PM
Benedikt Blitz, SMR Premium GmbH

The presentation will highlight the recent developments in the world of Forged Special Steels and remelted steels (nickel alloys, stainless steel, alloy tool steel) as well as will give an overview about end-user demand and structures of these special steels and also summarize the actual status of installations (forging presses and remelting units) on a global scale. The speech will also focus on the production of Metal Powders and Powder Metallurgical Steels and especially its associated production technologies like HIP, MIM and AM. As they are and will become key future core technologies for a number of demanding products and thus for the usage in different associated industries. The presentation will also highlight the actual supply and demand situation of metal powders and the manufactured metal powder steels, will introduce leading manufacturers of both powders and steels, and summarizes installed capacity and new capacity that are on the way.


AMPM Abstracts



SESSION A04   Titanium Alloys


012 - Effect of Atomization Method and Post-Processing Treatments on the Microstructure and Mechanical Properties of Ti-6Al-4V Alloys Manufactured via Laser Powder Bed Fusion
Leandro Feitosa, Sandvik Machining Solutions AB 

Due to the rapid development of AM technologies, special attention is necessary towards reducing processing defects and achieving dense and homogenous materials. In this work, the assessment of Ti-6Al-4V powders fabricated via two of the mostly developed atomization processes, advanced plasma atomization (APA) process, which uses plasma torches to melt and atomize the metal wire feedstock, and electrode induction melting gas atomization (EIGA) is thoroughly carried out. Following production of parts by laser powder bed fusion (LPB-F) and post-processing treatments, which includes stress relief and hot isostatic pressing (HIP) treatments, the resultant mechanical properties at room temperature are reviewed. Microscopy study aimed to detect and discuss the level of microstructural damage and texture and their influence on the performance of pre and post heat-treated parts to obtain optimal parameters to achieve superior properties. A comparison is made between the effect of these stages and traditionally cast and HIPed Ti-6Al-4V alloys.

041 - The Effects of Surface Finish on the Fatigue Performance of Additive Manufactured Aerospace Components
Lauren Ednie, Institute of Structural Materials—Swansea University

Additive layer manufacturing (ALM) is an advanced manufacturing technique whose uptake within the aerospace industry is being limited by the lack of understanding on the effects of surface finish on the fatigue properties of ALM built components. It is known that the surface profile of as-built ALM parts is significantly rougher than its traditionally manufactured equivalent, promoting stress raising features which have an adverse effect on fatigue life.

This paper will focus on recent research carried out at Swansea University to understand the fatigue properties of the popular alpha-beta titanium alloy, Ti-6Al-4V, as manufactured through electron beam melting (EBM). Results have been generated on as-built and machined & polished EBM test coupons, supported by fractographic analysis and advanced surface profilometry.

143 - Investigation of the Influence of Oxygen Homogeneity on the Processability and Properties of Additively Manufactured Ti-6Al-4V Parts 
Mahdi HabibnejadKorayem, AP&C Advanced Powders and Coatings, Inc.

The chemical composition of powder feedstock could influence powder physical properties as flowability, free packing ability, and consequently, the final properties of printed components. For the case of Ti-6Al-4V alloys, one of the main elements influencing the final properties of printed components is the oxygen content, which can be distributed at either the interstitial free positions or surface forming different grades of 23 and 5. In general, the main criterion to select among the above material grades is the fact that higher oxygen content of the grade 5 would enhance the strength results and the lower oxygen content of the grade 23 would result in superior ductility. The mixture of the above grades could also yield the target oxygen content but would bring inconsistency and heterogeneity in the localized oxygen distribution. This paper is to present the experimental data to clarify the uncertainties introduced to the L-PBF processability of the uniform and mixed powders and comment on the final mechanical and physical properties of L-PBF printed components. For this purpose, two powder batches containing grade 23 and a combination of grades 5 and 23 have been designed and processed by L-PBF process to assess the resulted microstructure. Also, the correlation amongst the microstructure and tensile properties have been discussed by an emphasis on the influence of promoted alpha phase formation. 


SESSION A05   Metal AM Testing and Evaluation


191 - Utilization of Digital Twin Quality Assurance of Metal Additive Manufacturing
Juha Kotila, EOS Finland - Electro Optical Systems Finland Oy

The latest camera based optical tomography (OT) and photo-diode based melt pool monitoring (MPM) systems have enabled detection of emission signals directly from melt pool of powder bed AM systems. With suitable algorithms these signals could be converted to process quality indicators correlating to process defects and microstructural defects found inside the actual parts of different materials.
This presentation will present how the defects could be found from OT and MPM signals of different AM processes. Moreover, how this information could be correlated with actual process and microstructural defects of real AM parts found using optical microscopy and computer tomography (CT) methods. Information can be used set the in-built quality assurance criteria for different AM parts and to generate effective digital twin of the AM part manufacturing process.

006 - Benefits of In-Situ Monitoring in Metal Additive Manufacturing
Michael Juhasz, FormAlloy

Metal Additive Manufacturing processes such as Directed Energy Deposition (DED) can produce complex geometries with incredible benefits for applications, but there are challenges between concept design and producing a part. In order to create quality, repeatable parts, in-process monitoring can be utilized to both collect data and control the build process. The data collected can help determine the point of failure initiation, and with implemented control in place, self-correction is possible during the build process. With Directed Energy Deposition various monitoring and control modes are available to reduce parameter development times, improve build quality, and limit operator input during a build. Among these control modes are melt pool size and temperature, powder flow, laser power, and geometric monitoring and control. These control modes not only significantly reduce the process parameter development cycle, but also result in a higher quality build to include density and material properties. 

156 - Development of a Surface Roughness Measurement Sample and Its Use in Sinter-Based Metal Additive Manufacturing
John Reidy, Desktop Metal

Rapid advancements have been made with metal Additive Manufacturing (AM) technologies based on both melt-based and sinter-based processes. The result is the need to develop a simple metal part that can account for most of the surface roughness conditions that evolve on different planar surfaces during processing. For example, processes based on fused filament fabrication (FFF) yield different surface roughness conditions on the top and bottom faces as well as along the planes in the z-direction. At the same time, processes that involve the spreading of a layer of powder followed by the application of either binder, laser or e-beam, can have subtle variations in surface roughness on different planar faces. Focusing on the extrusion-based FFF process, this investigation discusses  the efforts to design a new part with 10 surfaces that can address the majority of the surface roughness variations on different planar orientations.


SESSION A06   AM Powder Characteristics II


116 - Linking Rheological Properties of Metal Powders to Spreadability for Powder Bed Based Additive Manufacturing Process Optimization
Aurélien Neveu, Granutools

Metallic powders are widely used in powder bed based Additive Manufacturing (AM) processes, with for example Selective Laser Melting (SLM) and Selective Laser Sintering (SLS). During such operations, successive thin layers of powder are created with a ruler or with a rotating cylinder and then partially sintered with an energy beam. The layer thickness defines the vertical resolution, a thin layer leads to a better resolution. Moreover, the spatial homogeneity of the layer is a key parameter to ensure good quality of the built parts. 
Visual observation of layer homogeneity is usually the only way for operators to quantify the spreadability of powders during the recoating. However, relating the powder characteristics to its spreadability beforehand should provide a more cost-effective way to classify and select the optimal powder and recoating speed combinations. 
Four metallic powders (AlSi7Mg06, Al-Mg-Sc alloy, and Inconel materials) commonly used in AM have been selected. Powders flowability has been determined with a rotating drum enabling to quantify the influence of cohesion, shear-thinning/shear-thickening as well as thixotropic behavior. These measurements have been correlated to the powder spreadability in a 3D printer, where a CCD camera is used to take several snapshots at different recoater speed. The obtained results show  good correlation between the cohesive index and the spreadability of the powder.

120 - Understanding Powder Morphology and Its Effect on Flowability Through Machine Learning in AM
Srujana Rao Yarasi, Carnegie Mellon University

The use of computer vision and machine learning tools in the additive manufacturing domain has enabled the quantitative investigation of qualitative factors like powder morphology, which affect the flowability in powder bed fusion processes. Flowability is measured through rheological experiments.  Convolutional Neural Networks (CNN) are used to generate feature descriptors of the powder feedstock, from SEM images, that describe not just the particle size distribution but also the sphericity, surface defects, and other morphological features of the powder particles. These descriptors are then correlated to their respective flowability properties for numerous powder systems to evaluate powder performance in an AM powder bed fusion machine. This framework is intended to be a powder qualification system that can differentiate between powder systems and serve as a method to indicate the usability of recycled powder lots, for instance.

224 - Heat Treatment Effect on Tribocorrosion Properties of Bio-Implants
Ali Afrouzian, Washington State University, Pullman

Influence of silica coating in Ti6Al4V substrate to be used in load-bearing implants was investigated for their tribocorrosion, microstructure change, and hardness. Laser engineered net shaping (LENS™) method has been utilized for the silica deposition on the Ti64 surface. Accordingly, as processed or zero laser-pass (0LP), one laser-pass (1LP), and two laser-pass (2LP) processes along with Ti64 and directed energy deposition (DED) fabricated Ti64 samples have been tested. A positive shift in open-circuit potential (OCP) during linear wear has been observed and showed about 500, 450, and 650 mV increase for 0LP, 1LP, and 2LP compositions, respectively when compared to Ti64. One of the main reasons behind this significant increase is the formation of the titanium silicide (Ti5Si3) which is shown in X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), along with scanning electron microscope (SEM). Improvement in coefficient of friction (COF) and microhardness are also observed in coated samples.


Tungsten Abstracts



SESSION T02   Tungsten Heavy Alloys II: Additive Manufacturing


150 - Processing of Tungsten Heavy Alloy by Extrusion-Based Additive Manufacturing
Animesh Bose, FAPMI, Desktop Metal

Tungsten heavy alloy (WHA) is a class of liquid phase sintered composite material that consists of predominantly tungsten (typically 90 wt.% or more) grains dispersed in a matrix of two or more elements chosen from Fe, Ni, Co, and Cu. Due to its unique combination of properties including high density, strength, hardness, toughness and good corrosion resistance, these alloys have found numerous applications in diverse industries such as counter weights, sporting goods, kinetic energy penetrators, radiation shields, vibration dampening devices, etc. bound metal deposition (BMD) is an additive manufacturing (AM) technology that has its roots in metal injection molding (MIM) and a freeform material extrusion process of fused filament fabrication (FFF). The process is capable of rapid prototyping and low volume serial production of complex shaped parts. This paper reports on the preliminary investigations in the processing of a WHA composition using the BMD process.

033 - Properties of Tungsten Heavy Alloy Processed by Binder Jet 3D Printing
Salvator Nigarura, Global Tungsten & Powders Corporation

The properties of Tungsten heavy alloy (WHA) are influenced by the manufacturing process and they are very sensitive to minor changes in powder characteristics, alloy chemistry, processing conditions and final microstructure.   This study was carried out to evaluate the properties of WHA manufactured using binder jet 3D printing (BJ3DP). Specimens and parts were produced by printing a prealloyed spherical WHA powder followed by debinding and sintering under a H2 atmosphere. Through optimization of the printing and sintering parameters near-theoretical density was achieved. The mechanical properties were evaluated from tensile samples machined from printed bars and compared against the properties of specimens produce by powder metallurgy (PM)--cold isostatically pressed and sintered rods.  The yield strength, ultimate tensile strength and elongation of the BJ3DP WHA matched those of PM WHA. The results from this study confirm that BJ3DP is a reliable method to manufacture WHA parts.

190-R - Additive Manufacturing of Refractory Grid Structures—Historical Overview 
Juha Kotila, EOS Finland - Electro Optical Systems Finland Oy

The developments on laser beam properties of additive manufacturing equipment have enabled reaching higher and higher laser beam intensity levels. These high beam intensities have made possible to process materials with very high melting temperatures, e.g. refractory metals. Most of these materials are difficult or impossible process in conventional manufacturing methods to include thin walled sections, internal cavities or structures with significant weight savings.


Special Interest Program Abstracts



SIP 1-2   Improvement in Precision / Accuracy / Variation Control II: Equipment Advances


565 - Improvements in Parts Production Enabled by Full Cycle Closed-Loop Hydraulic Control
Heath Jenkins, Gasbarre Products, Inc.

The use of hydraulics in powder compaction has been a staple of the industry for many decades – enabling larger and more complex parts to be added to the scope of PM capabilities. Typical hydraulic press packages have retained mechanical functionality that yields decreased costs and increased simplicity. However, these mechanical features come with a downside by limiting the realization of the full benefits of closed-loop control throughout the compaction cycle. Today, advances in hydraulic control have enabled the full use of closed-loop control throughout the compaction cycle while limiting the cost/complexity impact. Discussion of these advances and the resultant capabilities improvements in terms of accuracy, repeatability, setup time, etc. will form the focus of this presentation.

572 - Highest Precision by Means of Innovative Press Solutions
Greg Wallis, Dorst America, Inc.

Powder metallurgy is a resource-efficient and sustainable procedure for the manufacturing of complex components. Nevertheless, further efforts will be necessary in order to meet the increased accuracy demands of the end customers, especially in the automotive sector, on the one hand and on the other hand to be able to economically compete with other manufacturing techniques in the market. An increased precision of the components after powder pressing respectively sizing leads to a further decrease in quality-related costs and significant reduction of reworking; ideally, some reworking steps might even become entirely unnecessary. This will not only lower part-specific manufacturing costs of known PM parts but might also make powder metallurgical manufacturing economically viable for part families that, until now, have been produced with alternative manufacturing techniques.

075-R - New Machining Enhancer for 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 show potential in replacing MnS used in various as-sintered steels. In this study, laboratory tests with powder-forged pucks and actual connecting rods were conducted to evaluate the performance of advanced machining enhancers in improving the machining of high strength powder-forged materials. Results obtained from machining tests and mechanical tests indicate that the advanced machining enhancers have potential in improving the machining of powder-forged materials and achieving higher productivity. The conclusion of the feasibility assessment in this study was to proceed with mass-production machining trials in order to validate the performance of the new machining additive.


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