PowderMet          AMPM          Special Interest          Carbide Forum

056 - Vacuum Sintering of High-Performance Pre-Alloyed Steel 
Amber Tims, PMT, North American Höganäs Co.

Vacuum sintering is a proven sintering method to improve mechanical properties while eliminating oxidation potential and atmosphere contamination in PM components. Recent progress in vacuum sintering technologies have made this sintering method become an attractive manufacturing process for PM materials aiming for property improvement and for the versatility and flexibility to control process parameters. 
Vacuum sintering furnaces are available in both batch and continuous configurations, with most furnaces utilizing the batch configuration. However, interest in continuous vacuum furnaces continues to grow due to increased production requirements and the advantages over batch vacuum furnaces for processing of larger production quantities. Currently, systematic studies are lacking to compare the vacuum sintering processes with conventional sinter methods for PM steels. In this paper, the sintering responses of a chromium-based sinter hardenable prealloyed steel were examined in a vacuum sintering furnace at conventional and high temperature with different cooling rates.

029 - Smart Solutions to Improve Sintering Atmosphere and Process
Liang He, Air Products and Chemicals, Inc.

The powder metallurgy industry is increasingly adopting Industry 4.0 technologies and solutions to improve production processes and product quality. Proper specification, measurement, and control of furnace atmospheres are always critical to achieving the desired metallurgical and mechanical properties. The combination of atmosphere measurements and other furnace operating parameters (e.g., furnace temperature and pressure) can provide a better view of the whole production. Thermodynamic calculations and field experiences can be integrated into the smart solution to provide process engineers more capabilities to manage and optimize production. In this article, our recent research and development work on smart solutions for the powder metallurgy industry will be presented and discussed. 

073 - Processing of High Entropy Al1.8-Cr-Cu-Fe-Ni2 via Powder Metallurgy
Daudi Waryoba, Penn State University DuBois

High-entropy alloys (HEAs) are presently of great research interest in materials science and engineering. HEAs typically contain at least five elements with equimolar or near equimolar, normally 5–35%, concentrations. HEAs differ from traditional alloys because of high-entropy effects, lattice distortion effects, kinetic delayed diffusion effects, and “cocktail” effects. HEAs have the potential to be used in many applications such as, high temperature materials, cryogenic materials, etc. The method traditionally used on industrial scales for preparing HEAs is the vacuum melting method. However, the development of HEAs has been hindered by microstructure defects caused by vacuum melting such as shrinkage cavity, shrinkage porosity, and segregation. This is the motivation for this study to investigate the prospect of using powder metallurgy for preparing HEAs. The results on the influence of the process parameters, e.g., sintering time, temperature, and atmosphere on the microstructure and mechanical properties of the final product will be presented.

012 - Rare Earth Magnets
Kalathur Narasimhan, FAPMI, P2P Technologies

Rare earth permanent magnets for the past 40 years dominated higher performance magnetic devices market. Raw material resource concentration in certain geographical areas threaten the market stability for rare earth permanent magnets. Material scientists have an opportunity to come through again. Use of elements such as nitrogen, nanostructure materials, and metastable materials are being explored. Electric vehicles are coming on stream as demand for greener energy grows. The motors require higher energy magnets and the need for more powerful magnets continues. This presentation reviews the developments and the challenges facing these alternate materials.

089 - Magnetic Properties of Ultrafine Grain Dy-Free Nd-Fe-B Sintered Magnets
Belle Finney, Ames National Laboratory

Strong permanent magnet availability is critical for electric vehicles to become increasingly prevalent. Although Nd-Fe-B magnets have superior ambient temperature magnetic strength, the addition of Dy is currently needed for use up to 150-180 °C in drive motors. Still, this heavy rare earth addition is not sustainable due to highly constrained supplies, i.e. an alternative must be found. Fortunately, ultrafine (<~3μm) grain size in Dy-free thin film Nd-Fe-B improves ambient and high-temperature magnetic properties. Using gas atomization with energetic jet milling may also be a scalable process to achieve this ultrafine grain size. To avoid oxidation in these ultrafine powders, a reaction gas can be introduced to the atomizer and the mill atmospheres to synthetically passivate/protect the powerful magnetic phase in these feedstock powders. SEM analysis will reveal the grain size and segregation spacing as a function of atomized powder size to guide processing. These ultrafine single-crystal particles could be ideal for alignment and full densification of Dy-free sintered magnets. Funding from DOE-EERE-VTO through Ames Lab contract No. DE-AC02-07CH11358.

001 - Production of Nd-Fe-B and Other Rare Earth Magnets Directly from the Oxides
Kalathur Narasimhan, FAPMI, P2P Technologies

Nd-Fe-B magnets are important in robotics, electric vehicles and number of electromagnetic actuation devices miniaturization. Nd oxide is available in the USA. Reducing the oxide to metal is generally achieved by electrowinning. However environmental concerns on the emissions and byproducts are of big concern. This presentation reviews the methods used and discusses method of direct reduction of oxides to make Nd-Fe-B magnets. 

050 - Influence of Particle Size Variations and Nanoparticle Coating on Flow Behavior of 316L Stainless Steel Powder and Mechanical Properties in Powder-Based Additive Manufacturing
Yannik Wilkens, SMS Group GmbH

In powder-bed-based additive manufacturing (AM) processes, the flowability of the powder is decisive for the quality of the manufactured part. Since fine particle fractions worsen the flowability, in the laser powder bed fusion (LPBF) process the lower limit of the powder fraction is usually 15 µm. Nanoparticle coatings can reduce the cohesive forces between particles. It has been investigated how the fumed silica (SiO2) nanoparticle coating affect the initial flow behavior of standard gas-atomized (15-45 µm) 316L powder and powders with modified particle size distribution (0-45 µm, 15-63 µm, 0-63 µm). It was demonstrated that flowability and bulk density increased as a result of the coating. Relative density and mechanical properties of the LPBF specimen showed similar results compared to the uncoated powder with increased tensile strength. The economic potential of coated powder for AM was demonstrated by the successful LPBF processing of fractions 15-45 µm and 0-63 µm.

080 - Additive Manufacturing Enabled Transition Joints Between Austenitic and Ferritic Steels 
Peeyush Nandwana, Oak Ridge National Laboratory

The difference in coefficient of thermal expansion (CTE) prevents joining of austenitic and ferritic alloys used in power plants. Further, the difference in carbon chemical potential results in premature service failure of these joints. We use blown powder additive manufacturing combined with thermo-kinetic calculations to design a transition joint between stainless steel 347H and grade 91 steel to reduce the CTE mismatch and obtain a shallower carbon chemical potential gradient. Our characterization showed that while the composition change was gradual, the phase change was abrupt, possibly because of the dilution during additive manufacturing. Despite the abrupt phase change we did not observe cracking at the interphase boundaries, but the dual phase austenitic-ferritic region served as a the failure point during tensile testing. We also subjected the samples to long term aging to determine the phase stability upon elevated temperature exposure.

098 - Extrusion-Based Metal Additive Manufacturing of 316L Using Highly Loaded Feedstock
John Reidy, Northwestern University

Powders with high tap density are of interest in extrusion-based metal additive manufacturing (AM) for their potential to produce highly loaded feedstocks. This paper reports the results of a high tap density 316L powder compounded into a feedstock at a loading of 70 vol.% and subsequently printed by bound metal deposition (BMD). The critical solids loading of the powder was determined by dynamic viscosity measurements at a range of solids loadings. Sintering of printed parts achieved densities of ~99%, at just ~11% shrinkage. Mechanical properties measured on the sintered samples were compared to values reported by MPIF Standard 35 for typical 316L produced by metal injection molding (MIM). The work presented shows the capability of high volume loading feedstocks in extrusion-based AM to reduce shrinkage compared with typical feedstocks, without deleterious effects to mechanical properties. 

135 - Materials Extrusion Additive Manufacturing (MEX-AM) of Copper Infill Structures for Accelerated Part Production
Aparna Munjuluri, University of Louisville

Material extrusion (MX) additive manufacturing (AM) combines fused filament fabrication (FFF) and sintering processes to create intricate metallic or ceramic structures using powder-filled polymer filaments. While MX-AM offers design freedom, it faces challenges such as differential debinding in complex parts, leading to cracking and failure. This study explores design and process strategies to mitigate these issues. Copper-filled filaments with 61 vol.% solids were used to 3D print lattice-based infill structures. Samples underwent direct sintering or debinding followed by sintering and were characterized for physical and mechanical properties. Results shed light on density, shrinkage, and mechanical properties for different infill densities (25%, 50%, 75%) using both sintering methods. Findings provide valuable insights for future research and industry, offering innovative strategies for 3D printing complex parts while addressing associated defects and challenges.

081 - LB-PBF Productivity Increase with Enhanced Al-Si10-Mg Powder
Sabina Kumar, Eaton Corporation

Laser-powder bed fusion (LB-PBF) is among the many additive manufacturing (AM) technologies that has found significant adoption across varied industrial sectors. Although sought out to be one of the popular AM technologies, the production rate of these systems is not suitable for mass production due to the use of a focused Gaussian heat source dispersion. However, recent developments in this area using multi-lasers and larger build volumes have increased the productivity of L-PBF systems, albeit at the expense of expensive machinery.
Our approach to achieving the requirement for high-productivity from the L-PBF system is by understanding the basics of the feedstock material and accompanying process parameters. In our study, we evaluated a novel high performance Al-Si10-Mg powder with uniform size, sphericity, and consistent microstructure. The metal powder has a specific particle size distribution (PSD), tap and apparent density and flowability characteristics that renders high productivity with LPBF. Process parameters were modified accordingly to meet the requirement of a high-productivity yield and equally dense part. From our study, we were able to push the bounds of build rates from our LB-PBF software to around 40cc/hr with the density of parts well above 99.5%. Surface measurements were taken to look at the surface finish of the as-fabricated part and monotonic mechanical properties were measured as well. Our study shows that we can drive up the productivity of the LB-PBF process by using an enhanced powder with unique powder characteristics. 

069 - Tribocharging as a New Method to Understand Thermal Debinding of Aluminum Powders in Additive Manufacturing Binder-Based Processes
Emilio Galindo, McGill University

Additive manufacturing binder-based processes, such as binder jetting (BJ) and metal fused filament fabrication (MF3) have lately gained attention due to its process flexibility and rapid build-in capability. Inherent to these processes is the addition of polymers used to join the powder particles when forming the green shape. The binder is afterwards removed utilizing solvent and/or thermal debinding prior to the sintering stage. Understanding the surface properties of powders after debinding is crucial to maximize the efficiency of the sintering step and producing high density parts. Tribocharging phenomena, which is based on electron transfer when two surfaces are placed in contact, can be used to determine changes of surface composition as any scale has specific surface characteristics. In this work, the possibility of using the tribocharging principle to understand surface powder degradation occurring after debinding process has been investigated. For this aim, Al-Si10-Mg powder processed with the MF3 technique was used.

407 - Additive Manufacturing I - Overview Examining the Different Processes and Powders
Zhuqing Wang, Kennametal

Cemented carbides, especially WC-Co, have been widely used in metal-cutting industry and wear resistant applications, due to the excellent combination of hardness and toughness. Additive manufacturing (AM), which builds 3D near net shape components layer by layer, has become an attractive option to fabricate WC-Co parts with complex shapes and low quantities. This presentation will be focused on reviewing the progress to date in additively manufactured WC-Co. It will provide an overview of both beam-based and sinter-based AM processes and powder feedstock and compare microstructure and material properties from different techniques. Challenges and suggested future directions for additively manufactured WC-Co will also be discussed.

409 - Fused Filament Fabrication of Hardmetals
Animesh Bose, FAPMI, Optimus Alloys, LLC

There is a growing interest in freeform fabrication of various materials, especially metals and alloys, ceramics, and carbides (hardmetals). The design freedom that is offered by various 3D printing technologies that have similarities with metal injection molding (MIM), have led to the proliferation of research and development activities in additive manufacturing (AM) of hardmetals. This presentation will focus on the developments around a form of fused filament fabrication of hardmetal known as bound metal deposition and show some of the similarities and differences of this technology with MIM.