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PowderMet          AMPM          Special Interest

PowderMet Abstracts


PM-7-1   Alloy Development

040 - Sustainable Alloy for Powder Metallurgy (PM) Structural Components
Roland Warzel III, North American Höganäs Co.

Sustainability is a growing trend within society and the automotive industry. Powder metallurgy (PM) is already recognized as a green technology through its use of recycled materials for raw material production and high material utilization compared to other metal forming technologies. However, an increasing focus on circularity and the rise of electrification challenges PM’s most popular material system – copper steels. Copper steels are widely used as they provide good mechanical properties matching the requirements of numerous applications. The recycling of copper steels can be challenging due the presence of copper in the material. Copper is also a vital component to electrification and stability of supply in the future is uncertain. A new PM alloy has been developed to provide the mechanical performance of copper steels without using copper as an alloying element. This paper will detail the properties of the new alloy in comparison to common copper steels.

066 - Development of PM CoNi-Based High Entropy Superalloy for Sustainable Manufacturing Technologies 
Ahad Mohammadzadeh, IMDEA Materials Institute

High entropy alloys and Co-based superalloys can be considered critical materials in the aerospace industry due to their excellent economic value and developmental potential. In this research, a novel and affordable high Cr CoNi-based high entropy superalloy (HESA) was designed according to the following: selecting a composition with a configurational entropy of higher than 1.5R, calculation of phase diagrams (CALPHAD), higher gamma prime volume fraction and solvus temperature, and low density (≤8.5 g.cm-3). The design strategy and CALPHAD results were validated by casting and the corresponding powder of the target alloy produced by gas atomization. Then, the developed powder was consolidated using spark plasma sintering at different sintering temperatures. The microstructural features and physical and mechanical properties of the developed alloys were characterized.
The results showed that after homogenization heat treatment at 1,250 °C, it is possible to obtain an FCC single-phase matrix with finer gamma prime precipitates. Also, the thermal analysis results and microstructural investigations on the aged samples showed that the gamma prime solvus temperature is about 1,150 °C with an approximately 70% gamma prime precipitate. In the end, the advantages and disadvantages of the CALPHAD predictions compared to experimental results are discussed on the as-cast and SPSed samples, and a novel and affordable design strategy based on the configurational entropy is introduced for the development of the advanced materials for high-temperature application and sustainable manufacturing technologies.  

099 - Multiple Memory Shape Memory Alloy by Altering Ni-Ti Alloy Ratio
Ram Narayan Gunjur, California State University, Sacramento

Shape memory alloys are materials that have the ability to memorize shapes. The unique quality of a material to remember shape based on temperatures is explored. This quality of the smart material is the shape memory effect, where the material can remember the ability to remember the shape given at high Austenite temperature and can remember those shape in the low martensite temperature. This unique ability of the material to memorize the shape has a valued application in the actuators, biomechanics. Etc. This research explores to increase the ability of the smart material to memorize multiple memories at different temperatures by using the powders of Ni and Ti. Apart from this the research explores manufacturing different alloys ratios to form a single specimen

PM-7-2   Powder Injection Molding

090 - Tighter Tolerances and Larger Metal Injection Molded Parts Using Highly Uniform, High Density Multimodal 316L Stainless Steel Powders
Joseph Schramm, Uniformity Labs, Inc

The achievable tolerances of parts made by metal injection molding are determined by sintering shrinkage and uniformity of sintering shrinkage, which are, in turn determined largely by powder loading and uniformity of powder loading in the molded green part. The current state of the art somewhat limits the maximum size of metal injection molded parts. Here, multimodal mixtures of high purity spherical 316L stainless steel powders having high tapped density and high spatial uniformity have been produced utilizing a very high fraction of an atomizer distribution to produce highly loaded feedstock and molded into parts showing sintering shrinkage of around 12%. In addition, these high-density powders retain manageable flowability when compounded into MIM feedstock, and can provide 1000x more contact points hereby facilitating the sintering process. The current work endeavors to exhibit tighter tolerances due to reduced sintering shrinkage and repeatability of sintering shrinkage. The performance of these multimodal mixtures has the potential to open metal injection molding to a broader range of potential applications with notable benefits, such as the production of larger parts or more precise smaller parts and the potential reduction or elimination of secondary operations. Furthermore, the powders discussed here utilize a larger portion of an atomization curve resulting in less material waste and a more efficient supply chain.

022 - Design and Development of Intermaxillary Dental Screw via Metal Injection Molding
Faiz Ahmad, University of Technology Petronas

A dental implant is a surgical portion that attaches to the jawbone and protects a dental prosthesis like a crown, bridge, denture, or facial prosthesis. Self-drilling intermaxillary fixation screw is often used in the intermaxillary fixation system as an orthodontic anchor and for reconstructive jaw operations. Titanium is a well-known element that has been used in the development of dental implant screws due to its biocompatibility, which allows for strong bonding with human bone and high mechanical properties. However, because of the difficult processing measures, it is expensive, and failures about the negative effects of Titanium accumulation on the human body have been reported. To manufacture the intermaxillary dental screws (IMDS), 62% 316L stainless steel, 3% nano-titanium Powder as a reinforcement, and 35% wax-based polymeric binder were chosen. The stainless-steel mould was used to produce the IMDS, with the specifications of the best possible mixture of powders and binder formulation which was being modified to optimise the manufacturing conditions. The feedstock preparation was followed by the conventional powder injection moulding process. The physical and mechanical properties of the Intermaxillary Dental Screws were determined through density measurement testing, hardness testing, and corrosion testing, and the materials' microstructural properties were analysed through a scanning electron microscope. Finally, optimization of the processing conditions was achieved, which led to high densification, minimal shrinkage in sintered parts, good surface morphology, and uniform characteristics.

189 - Processing and properties of MIM Ti-6Al-4V in Two Binder Systems
Lane Donoho, Advanced Metalworking Practices

Optimally processed MIM Titanium-6Alumium-4Vandadium offers excellent corrosion resistance and strength to weight mechanical properties.  This paper considers processing of Ti-6Al-4V utilizing two binder systems – one being POM-based and the other being wax-based.  The molding, debinding and sintering process parameters will be outlined.  The properties and results of mechanical testing will be compared.

AMPM Abstracts


AM-7-1  Powder Properties

171 -Recycling of Oversize Additive Manufacturing Powders
Aamir Abid, Retech Systems LLC.

The demand for additive manufacturing powders is expected to grow over the next several years as the technology scales to production. In order to achieve broad adoption of AM, the overall production costs need to continue to decrease. The powder costs are a significant input to the overall cost for AM and an active area of research and development in the industry. Gas atomization is one of the processes by which high-value AM powders are produced on an industrial scale. Only a fraction of the powder distribution produced by this process is utilized by AM. For example, for laser powder bed fusion (LPBF) modality, the typical usable powder size range is between 15 – 63 um. The as-produced powder distribution via gas atomization is broader and results in the production of oversize powder that is not utilized for AM processes. There is an urgent need to develop solutions for recycling oversized powder and reducing the overall cost of the AM feedstock.  Retech has developed a powder consolidation system that recycles oversize powders into high-value ingots. The system is designed to feed a broad range of alloys including nickel, titanium, and other reactive and refractory powders. In this work, we describe the performance of the powder consolidator, the characteristics of the ingots produced from powder and the economic model for powder recycling.

089 - Solutions for Increasing AM Grade Powder Yield and Reverting Over Sized Powder, Especially for Titanium Powder Production
James Sears, Amaero Additive Manufacturing

It is well known that atomized powder production results in a rather wide distribution of powder sizes. Unfortunately for metal powder producers, powder used in the Additive Manufacturing Industry consumes only a fraction of the powder produced. This leaves the producers with excess material that is difficult to sell and therefore will be scraped or recycled. Depending on the alloy, recycling can be as easy as returning the powder to the melt. However, certain alloys like titanium pose a challenge to remelt due to reactive nature of this material.
Two solutions are presented to help alleviate this problem. First an atomizing technique that is tunable: easily changing powder size distribution to fit end user needs. The second, mainly for reactive metals like titanium, is a single step melting system that uses powder as feed stock to produce bar materials directly suitable for reprocessing. 
Preliminary results from pilot studies for both solutions will be presented. 

195 - Predicting Powder Spreadability For Metal AM
Aurélien Neveu, Granutools

Metallic powders are widely used in 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. In order to obtain a thin layer, the powder is as fine as possible. Unfortunately, when the grain size decreases, the cohesiveness increases and the spreadability decreases. Consequently, the spreadability must be good enough to obtain homogenous successive layers. The quality of the build parts is thus directly related to the powder flowing properties.  In a previous study, the spreadability of metal powders has been shown to be strongly linked to their rheological properties measured in a rotating drum. This first investigation highlighted the importance of powder rheology on spreadability, especially when varying the recoater translational speed. In the present work, a more extensive experimental study has been carried on to complement the previous results, with in situ evaluation of the spreadability in the printer. To evaluate the spreadability, several powder layers are deposited with the recoater, and pictures of the powder bed are taken after each recoater pass. An image analysis processing is then applied to extract the interface fluctuation, a measure of the homogeneity of the layer and thus the spreadability of the powder. The spreadability is then correlated with the cohesiveness and rheology of the powders evaluated in the rotating drum. A specific focus has been put on understanding how the recoater velocity influences the spreadability depending on the powder's rheological behavior. Indeed, proper knowledge of the powder/recoater interaction is essential to predict powder performance during the recoating, to determine the optimal processing parameters, and therefore provide a more cost-effective way to classify and select the optimal powder and recoating speed combinations.

AM-7-2   AM Case Study

177 - Application of Additive Manufacturing to Deliver Incremental Production of Conventional Powder Metal Components without Compaction Tooling
Stephen Feldbauer, Abbott Furnace Company

The conventional powder metal industry has always struggled with distributing the cost of compaction tooling and the need to maintain a competitive price of the final product.  The result has historically limited the order size to high volume orders. Although additive manufacturing of metal components has become more accepted.  Additive techniques, such as laser powder bed fusion and traditional binder jet printing, have been focused on the production of small spherical particle sizes and materials that are less susceptible to oxidation, like 316 and 17-4.  This has prevented the application of AM as a low volume process to complement the conventional press and sinter production of traditional powder metal chemistries and parts. Recently, a new approach to additive manufacturing has provided a technique for the printing of conventional powder metal chemistries and particle size distributions.  Using an FC-0208 powder, the physical properties and processing requirements will be reviewed to assess the application of this printing technique to expand the market for conventional press and sintering manufacturing.

058 - Current Challenges and Comparison of Precision Manufacturing through Binder Jetting and Laser-Based Powder Bed Fusion
Anok Nagaram, Chalmers University of Technology

Additive manufacturing (AM) technologies enable manufacturing of complex design as compared to traditional manufacturing methods. There is an enormous opportunity to explore this technology which aids the evolution of its process to acceptable manufacturing method. This work focusses on the efficacy of the dimensional and tolerances of the AM parts with focus on small features which are typically required in the applications such as waveguides, filters and antennas applicable for telecommunication services in the millimeter-wave frequency range. The objective is to design, manufacture and test small features for and analyze using resonance frequency (RF) measurements. In this study, precision parts were manufactured using binder jetting (BJT) and powder bed fusion-laser beam/metal (PBF-LB/M) and the geometrical deviations at small features were measured and compared among both these techniques. The deviations of these artifacts are characterized using stereo optical microscope (SOM) and scanning electron microscope (SEM) with respect to their position during the printing process. It is found that parts manufactured using BJT and PBF-LB/M have surface roughness, with powder particles fused to these small features, subject to orientation and strategies. Printing was focused on obtaining accuracy in the range of micrometers and measured resonance frequency (RF) close to the nominal 27.9 GHz with minimal spread between samples. 

075 - Applications of Additively Manufactured Porous Media in Thermal Management, Filtration, and Flow Control
Vincent Palumbo, Mott Corporation

Conventional powder metallurgy techniques relying on compaction and sintering have been in use for decades to fabricate porous media for precision filtration and flow control devices. Mott Corporation has developed methods of fabricating porous metal media utilizing Additive Manufacturing. The AM approach opens the door for unique design geometries that are impossible to accomplish with conventional pressing-sintering methods. Additionally, gradient porosity structures and unique performance improvements have been realized under the additive development work. Mott uses laser powder bed fusion to generate filtration, flow control and thermal management media that exhibits nominal pore sizes covering ranges of sub-micron to 100+ microns. The enabling technology for this work is the open architecture of the additive equipment that supports discrete laser parameter adjustments. The ability to alter a wide array of laser parameters and build schemes not only helps fine tune the performance of the porous media, but it also greatly reduces the burden on the CAD file/slicing program itself. The work presented here discusses the pore structure development, impact of parameter settings on part performance, and highlights three case studies where the printed porous media is used in real world applications. 

AM-7-3   AM Materials

196 - Microstructures and Tensile Properties of 316L Stainless Steel Fabricated Via Laser Powder Bed Fusion
Melody Chepkoech, Howard University

The evolution of additive manufacturing (AM) has provided enormous freedom to the design and fabrication of parts with complex geometries. In this study, samples with 1.5 mm and 4.0 mm thicknesses have been used to investigate the microstructure and mechanical properties of LPBF 316L stainless steels. Tensile tests were conducted at a strain rate of 0.001 s-1. The 1.5 mm thick sample exhibited a slightly lower yield strength of 538 MPa, tensile strength of 606 MPa, and elongation to failure of 69 %  than the 4.0 mm thick sample that had yield strength of 551 MPa, tensile strength of 619 MPa, and elongation to failure of 73 %. 87 HRB and 93 HRB hardness values were obtained for the 1.5 mm and 4.0 mm thick samples, respectively. Optical microscopy confirmed the formation of melt pools, a typical feature of additively manufactured materials. Scanning electron microscopy showed the presence of dimples at the samples' fracture zones, demonstrating a ductile fracture mode. Columnar grain structures with fine cellular subgrain structures were formed along the build direction. A texture of  {001} <101> was obtained for the undeformed samples. However, when plastic deformation occurred, a texture transition to {111} <001> for the 1.5 mm thick and {111} <011> for the 4.0 mm thick samples along the build directions was observed. Additionally, the grain boundary maps demonstrated an increase in the number fraction of high-angle grain boundaries from 21.9 % to 45.9 % for 1.5 mm and 18.3 % to 48.4 % for 4.0 mm thick samples due to plastic deformation. The kernel average misorientation maps revealed the pre-existence of dislocation networks. The geometrically necessary dislocation densities of the samples were calculated as 1.2 x 1016 m-2 and 1.4 x 1016 m-2 for the 1.5 mm and 4.0 mm thick samples, respectively. 

060 - AM Using Novel A8 Tool Steel Powders Produced by Water Atomization
William Chaîné, Laval University

Most additive manufacturing processes use gas atomized metal powders as feed material. Development of metal powders for AM produced by water atomization could bring significant advantages related to powder production rate and therefore cost reduction for alloys of interest able to be produced by this technique. Given recent developments allowing the production of regular (almost spherical) particles by water atomization, the fabrication of tool steel powders by this approach is worth exploring. It can be shown that water atomization of ferrous alloys can be tailored to yield powders with similar and even better properties than gas atomised powders. This study shows properties of AM components made from A8 tool steel powders that were water atomized and improved by different techniques such as plasma spheroidization, heat treatment and diffusion alloying.

008 - Additive Manufacturing of Embedded Thermocouples in WC-Co Cutting Tools for Cutting Temperature Measurement
Bruno Guimarães, University of Minho

During machining processes, a large amount of heat is generated due to deformation of the material and friction of the chip along the surface of the tool, especially in the cutting zone. This high temperature strongly influences tribological phenomena and adhesion, tool wear, tool life, workpiece surface integrity and quality, chip formation mechanisms and contribute to the thermal deformation of the cutting tool, leading to high operating costs and reduction of the end product quality. In this sense, being able to assess the cutting temperature in real time, at various points of the cutting tool during machining processes, is of utmost importance to effectively optimize cutting parameters and the cutting fluid flow adequately, for minimizing heat generation, temperature and consequently wear, allowing to increase tool life.
This work proposes the fabrication of embedded additively manufactured type K and type N thermocouples by laser powder bed fusion for real time cutting temperature measurement. Processing parameters optimization was performed to obtain a dense and continuous thermocouple with no significant defects and the emf of the additively manufactured thermocouples was experimentally determined. The obtained results show that this approach is effective to produce embedded thermocouples in WC-Co cutting tools capable of measuring cutting temperature, which will allow a real time optimization of the cutting parameters, namely cutting speed, feed and depth of cut, during in-service time, thus enhancing tool performance and life.

AM-7-4   Space Applications

111 - Metal AM with Green Lasers is Propelling the Next Generation of Space Exploration
Eliana Fu, TRUMPF Inc

Recent exciting developments in rocket engine propulsion have included copper alloy engine component manufacturing by metal AM, whether it be in C18150 (CuCrZr) or GR Cop. Copper alloy combustion chambers allow exceptional thermal conductivity and 3D printing will allow improved design and shortened lead time for the manufactured product.
Most typical AM processes involving lasers all use IR (infrared) wavelengths to rapidly melt powder either blown powder or on a powder bed but in fact, green laser light at 515nm, as opposed to infrared (1030-1064nm) is more effective for copper and other highly reflective materials.

Combining a green wavelength in a laser AM process and copper alloy powder results in a printed part with higher as-printed density, less spatter and better surface finish. The production efficiencies obtained with green lasers translate to bigger and better engines, improved thrust output and the bigger the payload or higher orbit can be achieved.

122 - High Pressure Cold Spray Additive Manufacture of GRCop Waveguides for Fusion
John O'Dell, Plasma Processes, Inc.

The high conductivity of copper makes it ideal for plasma facing components such as heat sinks and waveguides for fusion reactors.  However, first wall fusion reactor temperatures may be as high as 800 °C, where copper is a poor structural material. Recent development of a copper alloy, GRCop, provides a potential solution with near copper like conductivity with significantly improved strength at elevated temperatures. However, components produced from GRCop must be made using powder metallurgy techniques. Additive Manufacturing (AM) based on laser powder bed fusion (L-PBF) has recently been used to produce GRCop components, but component size is limited. Therefore, AM techniques based on High Pressure Cold Spray (HPCS) and removable mandrels, which can produce components 2m in length and greater, were developed to produce GRCop waveguides. Testing has shown HPCS GRCop has conductivity values ~80% of pure copper, which is ~15% greater than the conductivity of L-PBF GRCop. Profilometer measurements showed the internal surface finish of HPCS-AM GRCop was ~3µm Ra on unpolished mandrels, which was a 3-4 times improvement in the surface finish as compared to L-PBF GRCop.  Preliminary testing at MIT showed HPCS GRCop cavities in the as-deposited condition had equivalent waveguide performance to L-PBF GRCop cavities that have had their interior surface abrasively polished.  This paper will discuss the development effort along with test results.


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