PowderMet AMPM Tungsten Special Interest
SESSION P11 Processing PM Magnets
176 - Improvements to the Powder Processing of Near-Final Shape Alnico Magnets
Emily Rinko, Iowa State University
Alnico permanent magnets (PMs) are a recent system of interest as an attractive substitute for rare earth (RE)-based PMs. They have advantageous operating temperature ( < 500°C) and high magnetic saturation, and with increased coercivity, have potential for utilization in drive motors for electric vehicles and in other applications for strong magnets. Exploration of advanced powder processing for alnico have yielded partial texture in large-grained, and final-shape bulk PMs. Recently, unique alnico compositions (alloyed to improve coercivity, some with reduced Co) demonstrated promising grain growth kinetics and preferred texturing during stress-biased sintering, i.e., solid-state grain alignment (SSGA). In this quest for improved alnico, one-step vacuum de-binding and sintering seems critical to enhancing remanence and building on improved coercivity. These developments will be discussed along with other novel magnetic annealing conditions and their impacts on coercivity and energy product. Funded by USDOE and KC-NSC through Ames Lab contract no. DE-AC02-07CH11358.
128 - 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.
233 - Structure–Property–Processing Relationship in Heat-Treated Cu-Ni-Si Powder Metal Premixed with Aluminum and Alumina Additives
Austin Fairman, The Pennsylvania State University—DuBois
Sliding electrical contacts are used to pass electrical currents between the stationary and moving parts. These contacts are required to exhibit high electrical and thermal conductivity, and wear resistance. While all-carbon or all-graphite sliding contacts are used for high voltage and low-current densities, metal-graphite composites such as copper-graphite are used for applications that require low voltage and high current densities. The metal-graphite composites provide high specific electrical conductivity, satisfactory thermal conductivity, and superior sliding properties. These materials are mostly made by powder metallurgy because the components are usually mutually insoluble. This study presents the fabrication of copper-graphite electrical contact through equal channel angular processing (ECAP) and powder metallurgy. The results show improved properties compared to the conventional press and sinter (CPS) method. This is attributed to the presence of high density of lattice defects, such as high energy and high mobility grain boundaries. These defects have low activation energy and tend to enhance diffusion.
SESSION P12 Advanced Lubricants and Modeling
178 - High Performance Lubricant for High Density Applications and Warm-Die Compaction
Vincent Paris, Rio Tinto Metal Powders
In the challenging market of powder metallurgy, part manufacturers must find ways to compete with other manufacturing techniques. Hence, the capability to produce high strength parts is an interesting topic. Pressing to a higher density is a favored method to achieve high strength. Designing premixes with small amounts of organic additives is a practical way to improve compressibility. Lowering the lubricant content is possible if its lubricity is sufficient to prevent surface and/or tool damage. Warm die compaction is another common way to improve powder mix compressibility. In this paper, a new high-performance lubricant is introduced. Physical properties and surface finish were compared for mixes containing a common wax and the new developed lubricant. The ejection properties were also evaluated at temperatures of 60 °C and 80 °C. It is shown that high densities with no surface deterioration can be obtained by using lower content of this high performance lubricant.
019 - Comparative Evaluations of PM Characteristics of Commercial PM Lubricants in an Iron-Based Mixture Using Advanced Characterization Methods
Amir Shirani, H. L. Blachford Ltd.
Rheological characteristics of an iron-based premix with various commercial lubricants were studied using rotating drum and rheometer instruments. The objective was to investigate the different aspects of powder flowability using advanced rheology instruments and classic flowmeters. Density evolution of powder with various lubricants and powder cohesivity were investigated using tap density and rotating drum tools, respectively. In addition, powder flowability of conditioned and consolidated powder, were each evaluated in the rheometer. Die filling capability and powder flow at both room temperature and higher temperature and humidity conditions were compared. To evaluate green and sintered properties, powders were tested in each of a small lab and a semi-industrial press. Parameters such as compressibility, spring back and ejection properties were investigated under warm die conditions. This study provides information to support better understanding of powder flowability as well as how different lubricants can affect physical and green properties of a premix.
018 - Warm-Die Compaction of Low-Alloy Steel Powder Mix: Compaction Mechanics and Densification
Ilaria Cristofolini, University of Trento
Powder behavior in uniaxial cold compaction has been extensively investigated in previous work. The constitutive model of different powder mixes has been derived, and the influence of several variables, such as geometry, chemical composition, lubricant type and amount etc., has been studied in depth. This work focuses on the influence of warm die compaction. A commercial diffusion bonded low alloy steel powder, added with 0.6% wt. lubricant, has been used producing cylindrical specimens with two different H/D ratios, both in cold and in warm die compaction. Concerning warm die compaction, two different lubricants have been added. The constitutive model and the densification curves have been derived for all the powder mixes using the data recorded by the press, in terms of forces and displacements. Comparing ejection force and energy, the influence of warm die compaction, type of lubricant, and height of the specimens have been highlighted.
NEW SESSION 02 PM Applications I
232 - Impact of Powder Metallurgy in Hybrid and Electrical Vehicles
Dakota C. Stormer, The Pennsylvania State University-DuBois
With the increasing amount of Electric motorized vehicles being created, gives light to the powder metallurgy part production. Petrol and diesel prices continue to increase over time will eventually increase the production of the electric motorized vehicles. Parts will need to be made similar to the petrol and diesel motorized vehicles for the increased amount of electric cars being projected. From the transition to electric creation we could likely see less pollution being pumped into our earth due the motorized vehicles.
234 - Effectiveness of Silver Coated Copper Powder as an Interlayer for Diffusion Bonding of Silver-Graphite on Copper
Nathan S. Banner, The Pennsylvania State University-DuBois
The primary goal of this project was to study the adhesion between sintered compact silver graphite composite and copper powders that are useful for making electrical contacts. Electrical contacts must be composed of a metal with high conductivity. Silver has the highest conductivity, followed by copper. When using both of these materials, cost has to be taken into account. Also, the graphite the silver is alloyed with prevents the diffusion between copper and silver in bi-layer contact. Taking both of these factors into account lead to using a thin coating of silver on copper powder. Specific steps used in this project in achieving the primary goal was to deposit a thin coating of silver on copper powder, compact and sinter the thin laminate layers of silver-graphite and copper powder, and examine the bonding that takes place using the SEM.
235 - Bulk High Strength Ultrafine-Grained Silver Alloys Via Powder Metallurgical Approaches
Erik Sease, University of California, Riverside
Ultrafine-grained materials have gained interest in recent years due to their unique properties when compared to their coarse-grained counterparts. In this work, microstructural refinement to the nanoscale and grain size stabilization in dilute binary Ag alloys is achieved through mechanical alloying (MA) followed by consolidation with spark plasma sintering (SPS). The mechanical properties of this alloy are probed with micro-indentation, and the microstructure is examined with electron microscopy revealing the presence of nano-scale grains and dispersoids, significantly bolstering the strength of the material as compared to that of pure unalloyed silver. The results forecast the ability to process high-strength, high-conductivity Ag alloys for electronic and structural applications.
SESSION A13 Metal AM Applications Aerospace
047 - Influence of Vacuum Heat Treatments on Microstructure, Texture and Mechanical Properties of NiTa Alloy Fabricated by Laser Powder Bed Fusion for Sputtering Target Application
Cheng-Tse Wu, University of Toronto
Nickel-Tantalum (NiTa) alloy sputtering targets are used by the semiconductor industry to apply an amorphous NiTa thin film layer between the magnetic soft underlayer and substrate of a heat assisted magnetic recording hard disk drive by a physical deposition process. In this study, the microstructure and residual stress of NiTa alloy specimens fabricated by the laser powder bed fusion (L-PBF) and then annealed, are investigated to understand the feasibility of using the L-PBF combining with vacuum heat treatment (VHT) to produce an alloy sputtering target rather than by the existing method. Compared with the as-fabricated specimen, the columnar dendrites completely transformed into equiaxed grains after VHT. After annealing at a temperature of 1275 ℃ for 4 hours, a uniform equiaxed grain microstructure and the uniformly dispersed γ-Ta precipitate was achieved. The VHT treated L-PBF NiTa specimens have much finer equiaxed grain structures with average grain size of 1.7±0.2µm than that in the hot isostatic pressing (HIP) treated hot pressed (HP) NiTa specimens with 6±0.6µm. After VHT, the maximum compressive residual stress reduced from 180 ± 50 MPa to 20 ± 10 MPa due to the microstructure recrystallization process. In addition, the fine uniformly distributed equiaxed grain structures in VHT treated L-PBF NiTa alloy enhances the quality of thin film coating applied on the disc substrate. Compared with NiTa manufactured with traditional process (HP follow by HIP), VHT treated L-PBF NiTa alloy have a much finer equiaxed grain structure.
239 - Reverse Effect of Hot Isostatic Process for High Laser Input Energy During Selective Laser Melting Process on Ti-6Al-4V Alloy
Eunhyeok Seo, UNIST: Ulsan National Institute of Science and Technology
To achieve the high productivity and economic feasibility of SLM products, the scan speed should be dramatically increased together with laser power in the as-built specimens. Subsequent HIP process is effective to minimize the porosities, but leads to microstructural transformation by high temperature and high pressure. In SLM Ti-6Al-4V, microstructures changed from αʹ-lath martensite to Widmanstӓtten α-lamellar structure. Therefore, tensile properties were deteriorated by the segregation of β stabilizing atoms, which gave rise to inter-lamellar fracture. Surface roughness modeling confirmed that the high surface roughness not only causes stress concentration, but also affects microstructure changes leading to decrease in tensile properties. Different tensile properties were investigated in the as-built SLM Ti-6Al-4V specimen with very high scan speed (1800 mm/s) and laser power (350 W) before and after HIP process, and surface roughness effect was considered as in a macro- and micro-scope view.
175 - An Overview of Metal Additive Manufacturing for Aerospace & Space Applications
Deepak Madan, Danik Innovations LLC
This presentation will provide an overview on the adoption of Metal Additive Manufacturing (“AM” or “3-D Printing”) technology by the Aerospace and Space industries. These industries have been early adopters of the Metal AM Technology, for both commercial and military applications.
Metal AM Technology has some great attributes that make it a great fit for Aerospace & Space applications, such as: designing of complex components, allowing incorporation of multiple components into a single AM part, shortening product development cycles via rapid prototyping with scalability to low-volume production, extending product life by providing a route to produce obsolete spare parts, and creating a robust supply chain with ability to produce new components and spare parts on-demand.
The Aerospace & Space industries are utilizing or evaluating a range of AM-grade metal powders and AM technologies. AM materials of interest include: stainless steel, nickel alloys, cobalt alloys, super alloys, titanium alloys, and aluminum alloys. AM technologies adopted or being explored include: laser powder bed fusion, direct energy deposition, binder jetting, fused deposition, and friction-stir technology.
With recent advances in Metal AM technology, improved build quality, robust supply of metal powders, material reuse, ease of scalability, larger build size, and creation & adoption of industry standards is anticipated to result in a faster and wider adoption of Metal AM Technology by the Aerospace & Space industries.
SESSION A14 AM Powder Production II
012-R - 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.
219 - Effect of Powder Reuse on the Mechanical Properties of Selective Laser Melted Metals
Fernando Alamos, University of Notre Dame
Metallic powder reuse is a simple method to significantly reduce material cost for direct metal laser sintering (DMLS). However, continuous recycling of powder must not compromise part performance, especially in industries such as aerospace and medical products. In this study virgin 316L and 17-4 PH stainless-steels, and Ti-6Al-4V titanium powders were cycled eight times. Design of experiments (DOE) was employed to identify how parameter settings affect mechanical behavior and determine optimum settings for different reused feedstocks without compromising production quality. The study showed that recycling powder for 316L and Ti-6Al-4V did not affect mechanical properties, and the strength and ductility of 17-4PH decrease after one initial reuse before stabilizing. No variations on the bulk density, chemical composition, and powder properties were observed though reuses. Additionally, specimens were tested in rotating beam fatigue testing using the stair-case method. No significant changes in the fatigue strength were observed after eight reuse cycles.
237-R - Development of Spheroidization Process for Electrolytic Dendritic Iron Powders
Jay 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 a mean particle size of 325 Mesh were taken for spheroidization in a specially fabricated atmosphere controlled spheroidization apparatus to get the 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. A simulation model for analyzing forces and energy dissipation during spheroidization by using discrete element modeling. After spheroidization it was observed that there was a 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, the overall process for spheroidization of electrolytic iron powder has been established economically.
SESSION A15 Metal AM Build Processes II
040 - Toward Same Day AM Parts Production
Dan Gelbart, Rapidia
Almost all metal AM systems used today can not create a complex part in one day (24 hours). The laser based systems require many manual finishing steps (stress removal, support removal etc.). Most sintering based systems require debinding or some steps between printing and sintering (such as de-powdering, baking etc.), plus a long sintering cycle. The next goal would be to turn around parts in a much shorter time, which is possible but requires more engineering. This discussion is only about fully-featured AM systems, capable of complex internal structures (which creates a lot of the payback in AM). Some specialized systems based on laser metal deposition or melting wires are fast but can not create complex internal structures and are not part of this discussion.
The talk will cover the obstacle in speeding up the AM process and some potentially interesting ideas that were tested that have the potential of greatly speeding up metal AM.
150-R - 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.
225 - Effect of Porosity and Composition on Mechanical and Biological Properties of Additively Manufactured Novel Titanium Based Alloys
Sushant Ciliveri, Washington State University, Pullman
Surface porosity on metal implants has been proven to enhance osseointegration in orthopedic applications in vivo. At the same time, bulk porosities reduce the weight and elastic modulus thus preventing stress shielding. Additive manufacturing (AM) offers freedom of designing desired pore morphology to achieve required porosity on implant material in a single operation. Strength of such designed porous structures depend on overall volume fraction porosity, pore-morphology, pore-size and pore-pore connectivity. Since implants are under constant loading conditions in vivo, it is important to evaluate the strength of porous metals under compressive and shear loading. Ti6Al4V is most widely used material for load bearing orthopedic implants. Although CpTi has higher biocompatibility than Ti6Al4V, it shows lower strength than the latter. Our work is focused towards evaluating the effect of lower Al and V contents in Ti6Al4V towards mechanical and biological performance in comparison to that shown by Ti6Al4V and CpTi, respectively.
024 - An Investigation into the Factors Influencing the Microstructural Homogeneity of Sintered Hardmetals
Thomas Jewett, Global Tungsten & Powders Corporation
Hardmetal quality is related to the homogeneity of the sintered microstructure. The formation of oversized grains within a sintered body represent potential stress raisers, and may adversely affect the mechanical properties. Several production options are available to reduce the number of oversized grains in a sintered sample, including addition of dopants, dopant type, sintering temperature and WC carburization temperature. In order to better understand the strength of the various affects an experiment was designed to evaluate several of the production options. The current investigation utilized a submicron tungsten metal feedstock and investigated the effects of carburization temperature, dopant level of Cr3C2 and the sintering temperature on both the final sintered properties and the homogeneity of the microstructure. Statistical analysis of the results was conducted, revealing strong associations between selected factors and the outputs.
052 - Cavitation Erosion Characterization of Cemented Carbides
Núria Cinca, Hyperion Materials and Technologies
Cavitation erosion is a common mode of wear in flow control and fluid handling systems. To mitigate this degradation mode, hard alloys such as Stellites or hard facing coatings are commonly used for flow control or pump parts. Cemented carbides, however, generally present superior wear resistance than those materials due to their favorable mechanical properties’ combination. In this study, the cavitation corrosion-erosion performance of cemented carbides with submicronic WC grain size was evaluated in a 3.5 wt.% NaCl aerated solution at room temperature as a function of their binder volume and chemistry. The effect of the addition of secondary (cubic) carbides on the performance of these materials was also evaluated. Results show that, by proper tailoring composition and microstructural parameters, cemented carbides can outperform Stellite-6 by more than twice. It is then concluded that the use of cemented carbides for small to medium size components is beneficial for the lifetime extension of flow control assets.
181-R - Reinforced Concrete Drilling with Cemented Tungsten Carbide Drill Bits: Wear and Fracture Mechanisms and Predictive Failure Analysis Based on Finite Element Modeling and Weibull Statistics
Steven Moseley, Hilti AG
Rotary-percussive drilling in steel reinforced concrete subjects cemented tungsten carbide drill bits not only to intensive wear but also high mechanical loading which may lead to premature failure due to overload or fatigue fracture.
In this work, finite element (FE) simulation methods based on transient (dynamic) impact loading and quasi-static indentation have been used to describe the thermomechanical load spectrum acting on the drill bits. These simulations estimated the stresses and temperatures generated which were then correlated with the experimental findings regarding crack initiation sites and regions experiencing thermo-mechanically induced surface microstructural modification.
Additional FE simulations have been performed to predict the influence of the local cemented carbide microstructure on the fatigue properties and Weibull statistics have also been employed to estimate failure probabilities based on measured mechanical properties.
Together, these complementary methods enable confident prediction of component reliability in this challenging application. This paper presents an in-depth case study..
Special Interest Program Abstracts
SIP 2-2 Alan Lawley Memorial Symposium II: Fatigue/Mechanical Property
556 - Fracture and Fatigue in PM Materials: A Perspective from Powder Forging to AM
Howard A. Kuhn, University of Pittsburgh
Fifty years ago powder forging was pursued as a means to full density net or near-net part geometries, with the hopes of expanding application areas for powder materials. Research conducted under a federally-funded research program, THEMIS, directed by Professor Lawley, provided seminal insights that eventually led to commercialization of the process. It was learned that, while full density was essential to achieve optimum static mechanical properties, the mode of deformation to full density affected metallurgical integrity across collapsed pores and subsequent dynamic toughness and fatigue properties. These results resonate in current industrial efforts to bring additive manufacturing (AM) into the mainstream of manufacturing. Again, competitive static mechanical properties are achieved, intermediate between conventional casting and forging, but comparable fatigue properties remain elusive, even after HIPing. Perhaps the reason for this deficiency lies in the lack of shear across pore boundaries during AM processing, which was one of the key findings in early research on powder forging.
576 - Effect of Highly Loaded Volume on the Fully Reversed Fatigue Strength of Heat Treated Fe-Cu-C Steels
Paul Beiss, FAPMI, RWTH Aachen University
A quenched and tempered and a carbonitrided Fe-Cu-C steel were compared in fully reversed plane bending fatigue with notched and unnotched specimens at different densities. If the notches are characterized by elastic stress concentration factors Kt, the volume around the peak stresses diminishes with increasing Kt. Applying Weibull’s survival statistics, the effect of highly loaded volume on fatigue is quantified to predict the fatigue performance of components. There are competing concepts with the same claim. For the relative stress gradient concept it is shown that there is a loose, but systematic relationship between relative stress gradient and highly loaded volume. With regard to the different heat treatments, the carbonitrided steel outperformed the quenched and tempered version up to the sharpest notches, although after carbonitriding all specimens were through hardened and free of compressive residual stresses.
563 - Effect of Microstructure Heterogeneities on the Mechanical Properties of PM Steels
Carl Blais, Laval University
The typical microstructure of PM steels stands out due to the presence of porosity and its heterogeneity. Indeed, several alloying methods lead to inhomogeneous spatial distribution of alloying elements resulting in the formation of various metastable and stable phases after sintering and/or sinter-hardening. This characteristic is unique to PM steels and could constitute a significant advantage in the context of microstructure engineering. As a matter of fact, the volume fractions of specific phases could be optimized to improve strength as a function of applied stress and loading mode. Up to now, literature on this subject is somewhat contradictory. Some studies indicate that the presence of certain metastable phases could increase tensile strength and fatigue resistance while others suggest the opposite. This presentation proposes a review of the current knowledge about this fascinating topic.