PowderMet          AMPM          Special Interest

920 - Preparation of Re-W Powder Feedstocks Using Liquid Precursor Impregnation 

Rhenium-tungsten alloys are useful refractory metals due to their high-temperature mechanical strength, high density, and thermal conductivity. To produce a Re-W powder feedstock, pure metal or oxide powder precursors are typically blended or mechanically alloyed. Although this technique can be sufficient for conventional powder metallurgy, it is not suitable for additive manufacturing or other applications that require strict control over powder properties. This work applies a liquid precursor impregnation method to prepare Re-W powder feedstocks without altering the properties of the underlying W powder. The ability to produce various rhenium compositions on both fine 1-5 micron and spherical 15 micron W powders is demonstrated, and the powders are consolidated in a dilatometer to assess how this powder preparation influences densification behavior. The microstructure and compositional homogeneity of the consolidated alloys are investigated as well. Overall, this work evaluates a novel, facile power feedstock preparation method for refractory metal alloys.

046 - Mechanical Properties of Cemented Tungsten Carbide with Nanocrystalline FeNiZr Binder
Sean Fudger, U.S. Army Research Laboratory

The use of cemented tungsten carbide (WC) spans numerous commercial applications.  Due to the extreme hardness and high modulus provided by the WC phase combined with added plasticity and resulting toughness contributed by the cobalt (Co) binder, cemented WC-Co is a good candidate for cutting tools, ammunition, and mining equipment.  However, Co has been identified as a strategic and critical material from the Department of the Interior (DOI) and is "anticipated to be a human carcinogen" by the US Department of Health and Human Services (HHS).  Nanostructured FeNiZr is being evaluated as a plausible binder replacement to Co since it doesn't exhibit these concerns.  Consolidations of WC-FeNiZr powders utilizing commercial press and sinter technologies at Global Tungsten & Powders have generated fully dense samples with hardness and toughness values exceeding 13.5 GPa (1377 HV) and 11 MPa-m1/2 (10 ksi-in1/2) respectively.  Electron Backscatter Diffraction and Transmission Electron Microscopy are used to explain the structure-property relationship.

125 - Microstructural Study of a WC-316L Stainless Steel Functionally Graded Coating Produced by Laser Metal Deposition
Sindi Ndinisa, Stellenbosch University

In this study the effect of a composition gradient on the microstructure of a WC-316L stainless steel coating was investigated. The coating was deposited onto 316L stainless steel substrates using laser metal deposition, with the WC composition varying from 23wt.% to 90wt.% from the substrate to surface. A Design of Experiments approach was employed to produce the functionally graded coatings by varying the laser power and scanning speed. Porosity and coating thickness were determined using optical microscopy and image analysis. Scanning electron microscopy, energy dispersive spectroscopy, electron backscattered diffraction, and transmission electron microscopy were used to characterise the microstructure of the functionally graded coating layers including a detailed study of the interfacial regions.

193 - Furnace Advancements for the Removal of Lubricant, Curing of Soft Magnetics, and the Continuous Sintering of Binder Jetted Materials
Stephen L. Feldbauer,  Abbott Furnace Company

Lubricant Removal has been one of the most difficult problems in the sintering of conventional powder metal components; however, following over 10 years of research, a paradigm shift has been presented to the industry that allows the complete removal of lubricants in compacts that are 92% dense and under.  This has resulted in significant gains in uniformity and component properties.   As the Powder Metal Industry struggles to find new applications and join the movement to electric vehicles, soft magnetics have shown a great deal of promise for the future.  Conventional thermal process techniques are not optimized for the manufacturing of these products.  We will investigate a new approach to curing soft magnetics and provides flexibility to the producer, along with significant gains in efficiency.    As Additive Manufacturing, specifically Binder Jetting, becomes more widely accepted, there is a rising need for continuous de-binding and sintering of these products.  Using a minimalist approach to the optimized design of a continuous push furnace has provided an approach that has lower capital cost, less maintenance cost, and better quality.  We will talk about this new approach and how it compares to conventional vacuum processing that is commonly used.

019 - New Integral Sinter-Quench Furnace Design For PM Ferrous Parts
Ravindra Malhotra, Malhotra Engineers

Powder Metallurgy Sintering furnaces for ferrous parts have been optimized for production of plain and carbon parts. Sinter Hardening process has been developed by rapidly cooling parts coming out of the Sintering section using fan and heat exchanger to get desired cooling rates for modified alloys. However for conventional sintering and through hardening two different processes are used. This can be in house continuous or batch Sealed Quench furnaces for post Sintering operation. Alternatively sintered materials are sent to dedicated heat treater's plant for carburising or carbonitriding process using integral oil quenching system. Good results have been observed in a metallic muffle continuous hardening furnaces. It is worth exploring design features of a Sintering cum Hardening furnace using oil quenching. Combining Sintering basic primary process and secondary heat treatment process in a PM plant will have many advantages. A stable Sinter Quench process will reduce raw material powder cost as compared to a Sinter Hardening process. This new process will reduce multiple handling of Sintered parts. This continuous process will enhance PM reach in meeting industry demands with shorter delivery time and consistent quality. 

169 - Operating Economics of Roller Hearth Furnaces Compared to Mesh Belt Furnaces
Rajiv Mehta, Fluidtherm Technology Pvt Ltd.

The workhorse of the press & sinter industry, the mesh belt furnace (MBF), cannot be used for sintering above 1,150 °C (~2,100 °F) due to low belt life at higher temperatures. One alternative is the roller hearth fFurnace (RHF) that uses graphite trays for parts transport instead of a belt, compared to the MBF in which parts are either placed directly on the belt or on graphite/ ceramic trays over the belt. An earlier investigation of 600mm (~24”) furnaces of both types that was previously published showed lower energy consumption to the extent of 20% by the RHF, a consequent reduction of the total sintering cost & the added possibility of higher temperature sintering. Furthermore, the RHF design concept allows the construction of wider & longer sintering furnaces for higher throughput & lower unit cost than is possible with the MBF. In this investigation, a similar comparison of operating cost is presented for the RHF & MBF but with a larger width of 900mm (~36”), both operating at the same sintering temperature.

028 - Effects of Up-Skin and Down-Skin Parameters on Surface Roughness of Selective Laser Melting
Xuan Wang, California Polytechnic State University

This paper evaluated process parameters and their effects of on surface roughness in selective laser melting. Specifically, settings associated with up-skin and down-skin have been investigated to determine relevance. Test samples were designed with multiple surfaces to evaluate parameters effects over a variety of angled surfaces. A design of experiments was developed for up-skin and down-skin using various up-skin and down skin parameters. Surface roughness data was collected by profilometer and analyzed through statistical means. Samples were then cross-sectioned and melt pool characteristics were evaluated by electrochemical etching. For up-skin surfaces, it appears that higher energy densities have a positive effect on surface roughness but result in keyholing. Hatch offset could alter the formation of the melt pool across different angles. For down-skin surfaces, the surface roughness was affected by hatch distance and contour scanning power. As a result, the contour energy proportion and volume energy proportion should be investigated to control surface roughness during selective laser melting process.

123 - Increased Productivity and Metal Deposition Rates Enabled by the nLIGHT AFX-1000 Ring Mode Laser
Ken Davis, Amaero Additive Manufacturing

As a result of the continuous advancements in laser powder bed fusion (L-PBF), we find ourselves at an interesting crossroads.  While we were once challenged to print fully dense material with underpowered lasers, we now find ourselves unable to fully utilize the available 1KW of power in the lasers routinely being fielded in L-PBF systems.  We typically print with a nominally 80µ laser spot size for both contouring and hatching as a compromise of productivity, feature resolution and surface finish.  Attempting to print with much more than 500 watts often results in excessive keyhole porosity and condensate generation.  To combat this limitation and to increase productivity, some L-PBF systems employ multiple lasers, numbering from two to twelve.  Other systems utilize more of the available laser power by defocusing the beam to a much larger spot size for hatching, while refocusing back to the 80µ Gaussian spot for contouring.  Both approaches drastically increase the complexity of the L-PBF system and create more opportunities for defects.  The AFX-1000 laser allows nearly instantaneous switching between a Gaussian spot and several sizes of ring modes, without any complicated optics or electro-mechanical systems.  Having the ability to switch between these modes allows us to print with the highest possible energy and productivity for each material and application.  Recent experiments with the AFX-1000 have demonstrated the ability to print at layer thicknesses up to 150µ and with deposition rates exceeding 100 cc/hr.

154 - Additive Manufacture and Material Property Analysis of Crack-Free Electron Beam Melted Pure Tungsten 
Kurtis Watanabe, University of Texas at El Paso

Pure tungsten is a refractory metal and has been gaining interest for the use in nuclear fusion reactors as a plasma facing material. This material suffers from poor machinability due to being brittle at room temperature. Additive manufacturing (AM) is a layer-by-layer manufacturing method that is fundamentally different than formative or subtractive. Since the AM process is highly variable, the process and the resulting material properties need analysis. This talk discusses the use of Electron Beam Powder Bed Fusion machine parameters that allow the processing of that yields high density (>99%) tungsten. The build substrate and support structures are critical in the production of the final part. Energy densities greater than 400 J/mm3 led to >99% relative density of pure tungsten. Material properties of the tungsten parts are reported and compared to conventionally manufactured tungsten.  These experiments outline the challenges of manufacturing this refractory metal with this AM technology. 

095 - Preparation and Characterization of Aluminium Powder-Filled Modified-Polylactic Acid for Fused Filament Fabrication
Emilio Galindo, McGill University

Fused filament fabrication (FFF) has recently garnered attention due to its inherent process flexibility and rapid prototyping capability. Specifically, the addition of conductive components into a 3D printing build sequence has significant potential and has received substantial interest in sensing applications and energy storage devices, however high resistivity of 3D-printed filaments poses a challenge. Polylactic acid (PLA) is one of the most widely studied renewable and biodegradable polyesters that has been recently touted to be used as a substrate of conductive materials. In this presentation, we investigated the effect of the AlSi10Mg powder on the thermal and mechanical properties at a volume fraction up to 20% in a chemically modified PLA matrix. 
 

147 - Additive Manufacturing of Aluminum Alloy by Metal Fused Filament Fabrication (MF3)
Sihan Zhang, University of Louisville

This research investigated additive manufacturing of Al-6061 aluminum alloy via metal-fused filament fabrication (MF3). This work focused on using the MF3 process to fabricate Al-6061 test coupons and optimize the MF3 process parameters to obtain improved mechanical properties. Feedstock with 57 vol.% solids loading Al-6061 was prepared by mixing Al-6061 powders and a polymer binder, followed by extrusion to fabricate a filament with a 1.75 mm diameter. The 57 vol.% Al-6061 powder-polymer filament was used to print green tablets and tensile bars with a Prusa MK3S+ 3D printer. Experiments were designed to optimize the 3D printing process parameters to obtain parts with the highest green densities. The green parts were subjected to solvent debinding, thermal debinding, and, finally, sintering processes to remove polymer content and become dense Al-6061 tablets and tensile bars. The sintered parts were characterized for grain structure, sintered density, and mechanical properties, and their prosperities were compared to metal injection molded (MIM) specimens. This work aims to enable rapid, predictable, reproducible, low-cost, and accurate production of metal parts with 3D features, thereby significantly expanding the current additive manufacturing capability.

181 - Properties of Binder Jetted Aluminum 6061
Miranda Moschel, Kymera International

Metal binder jet printing is expected to greatly increase in market value in the coming years, and a key player in the development of binder jet technology is aluminum. Prized for its excellent strength to weight ratio and low cost, aluminum has been proven to be viable for use in binder jet printing. This is a  review of binder jet aluminum 6061 properties sintered in a continuous belt furnace. Evaluation of dimensional distortion and mechanical properties in as sintered and heat treated conditions will be presented.  

085 - Mechanical Properties of Additively Manufactured DuAlumin-3D Alloy Pistons
Alex Plotkowski, Oak Ridge National Laboratory

High temperature performance of aluminum pistons is very critical for combustion engines with increasing power density. In this study aluminum pistons were made of high temperature DuAlumin-3D (AlCeNiMnZr) alloy using powder bed laser fusion additive manufacturing (AM) process.  Mechanical properties of the AM pistons were evaluated in tensile, fatigue, creep and Charpy impact. The testing results show that mechanical properties of the AM aluminum pistons are significantly better than those of commercial high performance cast aluminum pistons.  At 300C, tensile and fatigue strengths of the DuAlumin-3D AM pistons are increased by at least 100% and 50%, respectively, in comparison with cast aluminum pistons.  The AM pistons also exhibit far superior creep resistance.

166 - Fusion Based Additive Manufacturing of Nb-Containing Refractory Alloys
Saket Thapliyal, Oak Ridge National Laboratory

Owing to their relatively lower density as compared to other refractory metals, Nb-alloys are promising candidates for next generation high-temperature materials for structural applications. However, these alloys are often difficult to process using conventional processing routes, such as machining. Therefore, the design of geometrically complex components using these alloys becomes cost-, time-, and labor-consuming. Furthermore, although casting is a route that is adopted to process these alloys, high oxidation tendency of refractory alloys and slow cooling rates during casting may lead to formation of coarse brittle phases that are detrimental to mechanical behavior. In this study, we investigate the chemistry-processing-structure-properties relationships of fusion additively manufactured Nb-containing alloys. Subsequently, the implications of rapid solidification during fusion-based additive manufacturing (F-BAM) on solidification growth mode and overall solidification behavior, elemental segregation, texture evolution, microstructural scale, and mechanical behavior are assessed. The effect of specific alloying elements on rapid solidification behavior, microstructural evolution, and ensuing mechanical behavior are also discussed. The chemistry-processing-structure-properties relationships of F-BAM processed Nb-containing alloys as established in this work are believed to enable design of light weight high temperature alloys for structural applications.

132 - Laser Powder Bed Fusion Processing of Superalloy 282 - Can AM Keep Up with Wrought Alloy Properties?
Abdul Shaikh, EOS Finland

While additive manufacturing (AM) has made considerable strides towards industrialization and application in recent years, wrought materials are still often viewed as the benchmark where metallurgical quality is concerned. This is particularly true for high temperature materials subject to creep and fatigue. Alloy 282 is one such alloy which originated as a wrought material, has seen rapid adoption in additive manufactured form. This study aims to better understand how AM laser powder bed fusion processed Alloy 282 compares to conventional wrought Alloy 282 in terms of microstructure and mechanical properties. Comparative evaluations of microstructure, grain size and shape, and room temperature and elevated temperature mechanical performance were carried out for laser powder bed fusion processed and wrought material samples. Analysis of the results summarizes the differences in performance and shows that with the correct heat treatment, laser powder bed fusion processed Alloy 282 can have performance comparable to the wrought alloy.

118 - Development of a Cobalt and Titanium Free Ultra-High Strength Maraging Steel for Laser Powder Bed Fusion
Eleonora Bettini, Sandvik Osprey Limited

Maraging steels are one of the most exploited commercially available ultra-high strength martensitic steels in laser based additive manufacturing (AM) processes. They offer the possibility of achieving tailored hardness-toughness levels by aging at different temperatures and times. Common maraging steels grades, as 18Ni300, contain relatively high amount of cobalt (Co) and titanium (Ti). However, Co has been recently strictly regulated due to its health, and environmental hazard, being classified carcinogenic. The addition of Ti to maraging steels contributes to the hardness and strength increment of the material. However, Ti has high affinity for oxygen and nitrogen, thus resulting in the precipitation of nonmetallic inclusions, detrimental to polishability and cleanliness of the mold steel. In this study, a new Co-free Ti-free lean maraging steel, capable of reaching similar mechanical properties compared with 18Ni300, has been developed. To address the needs of molding and tooling industry for the net-shape production of molds with thin wall structures, the proposed steel possesses very low carbon content showing minimal distortion after fabrication by laser powder bed fusion process (L-PBF). Finally, a specific focus has been placed on the surface aspects, that are fundamental to achieve the right performances of the parts. Thus, the polishability and the corrosion behavior of the new alloy have been evaluated both after conventional polishing, and after the application of DLyte® technology, the green and sustainable dry electropolishing technology. The results were then compared to 18Ni300. 

157 - Rapid Alloy Selection for Nickel Based Superalloys in Electron Beam Powder Bed Fusion
Christopher Ledford, Oak Ridge National Laboratory

New alloy design for additive manufacturing can be a lengthy and costly process. Here we explored new techniques to help down select candidate nickel superalloys for processing in electron beam powder bed fusion. Ultimately variants of LSHR were chosen for powder production and further processing. Microstructure and mechanical properties at elevated temperatures were explored as well. 

155 - Development of a Dual Phase Low Alloy Steel for Laser Powder Bed Fusion (LPBF)
Chris Schade, Hoeganaes Corporation

Development of low alloy steels for laser powder bed fusion is made difficult because high carbon levels are typically used to develop strength and hardness. These high carbon levels tend to lead to cracking due to the high levels of residual stresses due to the transformation of the microstructure to martensite.  Additionally, the layer by layer heating from the laser leads to a tempering of martensite leading to generally a softer material then the wrought steels.  By creating a dual phase microstructure a steel can be developed that has a range of mechanical properties that can be varied by post-printing heat treatments.  The microstructure can be varied from predominantly martensitic structure that exhibits high strength to a microstructure with high levels of ferrite leading to a steel that has high ductility and impact energy.  The mechanical properties and microstructures of these various heat treatments are reviewed along with potential applications including those in the automotive industry.

516 - Review of Mechanical Properties of PM Materials for FEA Modeling
Julie Campbell-Tremblay, PMT, Rio Tinto Metal Powders

FEA is used to optimize and predict mechanical performance of components, to reduce design times and the need for costly product prototyping. However, the modeling performance is dependent on the data provided to the design software. Static and dynamic properties of PM materials are not as widely available as they are for wrought materials and therefore can result in inaccurate predictions or even the impossibility to simulate because of inexistence of data. 
The objective of this presentation is to review what PM fatigue data is available in the literature, how they can be used in FEA modeling and what would be required to democratize the utilization of FEA fatigue modelling in PM part design.

520 - Trends & Standards Committee Update
Markus Schneider, GKN Powder Metallurgy Engineering GmbH

958 - Atomistic Modeling of Thermal Barrier Coating System to Investigate Interfacial Strength
Tejesh Dube, Indiana University-Purdue University Indianapolis

This study investigates the interfacial strength at topcoat/bondcoat and bondcoat/substrate interface for thermal barrier coating (TBC) systems fabricated using spark plasma sintering technique. Two atomistic models are built. The first model is a conventional TBC system with 8YSZ topcoat, NiCoCrAlY bond coat and 718 nickel base superalloy substrate. The second model incorporates the addition of Ti3C2 MXene layer between the 8YSZ topcoat and NiCoCrAlY bond coat. The MXene layer is added to slow down the oxidation of the bondcoat. Density functional theory (DFT) and molecular dynamics (MD) tools are used to study the atomic interactions at the interfaces and subsequently calculate the interfacial strength in ground state and at elevated temperatures. The results show that the addition of the MXene layer improves the adhesion between the topcoat and bond coat thereby creating a robust TBC system.