PowderMet AMPM Tungsten Special Interest
SESSION P17 Novel Materials
067 - High-Entropy Alloys: A New Opportunity for the PM Route—Part 1
Jose Torralba, FAPMI, Universidad Carlos III de Madrid
High-entropy alloys (HEAs) have attracted a great deal of interest over the last 15 years. These alloys appear breaking the alloying principles that have been applied for many centuries. Usually HEAs possess a single phase (contrary to expectations according to the composition of the alloy) and exhibit a high level of performance in different properties related to many areas in industry. -corrosion, mechanical properties, magnetic properties-. Most HEAs are processed by ingot metallurgy, being powder metallurgy (PM) an interesting alternative for further developing to possibly widen the field of nanostructures in HEAs and improve some capabilities of these alloys. In this paper, PM methods applied to HEAs are reviewed, but it also emphasizes many possible ways to develop the use of powders as raw materials and specially, how powder metallurgy is an opportunity to introduce changes in the microstructure that can improve even more the performance of these special alloys.
073 - High-Entropy Alloys: A New Opportunity for the PM Route—Part 2
Jose Torralba, FAPMI, Universidad Carlos III de Madrid
High-entropy alloys (HEAs) have attracted a great deal of interest over the last 15 years. These alloys appear breaking the alloying principles that have been applied for many centuries. Usually HEAs possess a single phase (contrary to expectations according to the composition of the alloy) and exhibit a high level of performance in different properties related to many areas in industry. -corrosion, mechanical properties, magnetic properties-. Most HEAs are processed by ingot metallurgy, being powder metallurgy (PM) an interesting alternative for further developing to possibly widen the field of nanostructures in HEAs and improve some capabilities of these alloys. In this paper, PM methods applied to HEAs are reviewed, but it also emphasizes many possible ways to develop the use of powders as raw materials and specially, how powder metallurgy is an opportunity to introduce changes in the microstructure that can improve even more the performance of these special alloys.
083 - Development of a New Cr-Based Hardmetal with Nanosized Tungsten Carbide Grain Size Through Liquid-Phase Sintering and Spark Plasma Sintering
Jose Torralba, FAPMI, Universidad Carlos III de Madrid
A novel Cr-based WC hardmetals having nanosized tungsten carbide grains has been developed using PM route. 1) it was used mechanical milling and press and sintering route. Extra additions of carbon and fine carbonyl iron were added to promote liquid phase sintering and sintering activation, respectively. By this manufacturing method density reach 97% of the theoretical one and good fracture toughness. 2) Consolidation by spark plasma sintering were proceed obtaining near full density and higher fracture toughness values. The effect of different carbon contents on microstructure, phase formation, is fully investigated and optimized to reach the best combination of properties
SESSION P18 Powder Metallurgy Standard Updates
168 - MPIF Conventional Powder Metallurgy Standards
W. Brian James, FAPMI, PMtech
An Update on MPIF Conventional Powder Metallurgy Standards
169 - MPIF Metal Injection Molding Standards
Michael Stucky, Norwood Medical
An Update on MPIF Metal Injection Molding Standards
170 - MPIF Metal Additive Manufacturing Standards
Animesh Bose, FAPMI, Desktop Metal
An Update on MPIF Metal Additive Manufacturing Standards
SESSION A22 Alloy Design & Development
121 - Development of Dual Phase Steel for LPBF Applications
Kerri Horvay, Hoeganaes Corporation
As additive manufacturing (AM) expands into the structural and automotive parts market more suitable materials need to become available that are tailored to these applications. For this study, a dual phase (DP) steel was chosen because of its combination of high strength and ductility. Its microstructure consists of two phases: islands of hard martensite and a soft ferrite matrix. Currently, DP steel is used in various automotive components that are produced by conventional manufacturing methods. The mechanical properties of laser powder bed fusion (LPBF) test specimens are evaluated as well as heat treated properties to show the range that can be developed with a single alloy system. This provides greater flexibility to the end user by allowing one material to be utilized in a range of applications. Microstructures and porosity are evaluated for both gas and water atomized powders and discussed in relation to build parameters and the mechanical properties.
162 - Phases, Properties, and Correlation to Theory in Rapidly Solidified Alloys Designed for AM
Emma White, Ames Laboratory
Ni-based superalloys, high strength aluminum alloys and multi-principle element alloys (MPEAs) are the next generation of alloys to take advantage of the complex geometries available through additive manufacturing (AM) as they have the desirable properties to make the greatest technological impact. However currently these alloys are difficult to build without defects. Utilizing calculations of thermodynamics, and energies of formation, the phases were predicted for various compositions of these advanced alloys designed for buildability. Samples of each were injection cast and re-melted to determine surrogate AM microstructures and characterized. The modeling efforts’ correlation to the experimental results show this approach to be extremely effective. A path towards optimizing properties within these alloys, while leveraging novel AM processing, has been demonstrated for property-driven alloy design for high temperature and extreme environment applications. This work was funded by the USDOE-EERE-Advanced Manufacturing Office and performed at Ames Laboratory under contract DE-AC02-07CH11358.
243 - NiCoMoTiAl High Entropy Alloying in DED/Additive Manufacturing Process: Investigation the Potential of CVM Powder Feeding System for Rapid Alloy Scanning
SeungJun An, Insstek, Inc.
High Entropy Alloys(HEAs) is attracting attention as a new material to be used in various industrial fields with its excellent physical properties that can adapt to extreme environments.
Especially in aerospace and the energy industry, the requirementfor alloys maintainingproperties athigh temperature environments is increasing,and HEAs are being studied intensively to solve its.
In this study, NiCoMoTiAl HEA with γ/γ'-phase which can secure high temperature characteristics is alloyed through DED/AM technology,and a new “Rapid Alloy Scanning” methodology using the CVM Powder Feeding System is suggested.
Each of the five elements comprising the alloy is manufactured from pure metal powders, withDED/AM technology in various combinations. This allowsthe rapid design of the proper portion of elements.
NiCoMoTiAl HEA produced via DED/AM with optimal content has been observed region and stable FCC structure through SEM/EDS/XRD analysis.
After heat treatment at 1,250℃, the γ/γ' phase was identified, and it has been demonstrated that the alloy hassuperior lattice parameter and solve temperature than previously studied alloys.
The methods used in this experiment are expected to overcome the physical limitations of existing alloy design methods and present novel methodological paradigms of FGMs, MMCs, and HEAs studies.
SESSION A23 Process History Effects on Final Properties
013 - The Evolution of Material Properties from Powder to Application
James Ashby, Liberty Powder Metals Ltd.
Two Stainless Steel alloys, 316L-Ti and 17-4PH, were atomized in multiple batches from the same pre-alloyed bar feedstock. These powders were then classified and used to produce test specimens across multiple production methods; Laser Powder Bed Fusion (L-PBF), Laser Directed Energy Deposition (L-DED), Hot Isostatic Pressing (PM-HIP), and Metal Injection Molding (MIM). This work explores the evolution from powder characteristics through sample production, across the aforementioned production routes, to the available mechanical, microstructural, and fracture properties. The conclusions drawn from this through-process analysis will be used to highlight the challenges inherent to existing metal powder quality assessment methods and procurement practices, and recommend supply chain solutions to address these from the perspective of new metal powder producer with a background in steel bar manufacturing.
022 - Effect of Heat Treatments on Mechanical Properties of Ultra-High-Strength Maraging Steels Fabricated by Additive Manufacturing
Faraz Deirmina, Sandvik Machining Solutions AB
In Metal Additive Manufacturing (metal AM) processes, especially laser powder bed fusion (L-PBF), there are many parameters that affect the microstructural development and consequently mechanical properties of built parts, such as thermal history, non-equilibrium solidification structure and meta-stable phase formation. These microstructural features can have a remarkable influence on the mechanical properties of parts after post-processing heat treatments. Generally, rapid solidification enhances the strength as a result of sub-structure refinement and increased dislocation density in martensitic steels. More importantly, non-equilibrium solidification might result in suppression of unwanted phase precipitation. However, inter-cellular micro-segregation accompanied by fast, non-equilibrium solidification might result in the formation of retained austenite, preferentially located at the cellular boundaries, which can affect the strength of maraging steel. Moreover, the presence of these phases might influence the aging (tempering) behavior. In this work, we report the effects of adapting different heat treatment strategies on the hardness, tensile strength, impact toughness and fatigue behavior of two different classes of ultra-high strength AM maraging steels aimed at achieving 54 and 60 HRC hardness levels.
078 - Quantification of Defects in Laser Powder Bed Fusion with Process Interruptions
Dana Drake, EOS of North America, Inc.
A failure during a component’s manufacture can often be correlated to distinct features observable during or after the manufacture or raw material processing (e.g. an impurity in an ingot, a forging crack, solidification porosity, or cracking during rolling). However, in additive manufacturing (AM), raw material feedstock undergoes melting, solidification and near net manufacture within the same process. AM processes can experience interruptions in the build process, or build pauses, due to any number of causes. Three identical builds endured three representative time intervals to simulate those pause length scales commonly encountered in Metal Laser Powder Bed Fusion (M-LPBF) and were compared to an identical, but unpaused build. Inconel 718 test coupons built on an EOS M290 Laser Powder Bed Fusion system were tested and characterized to provide insight into the effects of build pauses on the microstructure, porosity defects and changes in both local and bulk mechanical properties. There was a visible witness mark on the outer surface of all printed test coupons of all pause lengths that corresponded to the paused layer. While easily distinguishable on the surface, porosity near the paused region and the mechanical properties over that region evidenced little, if any change. The microstructural indications were subtle, but distinguishable in the etched condition. The witness mark stands out in contrast due to the built part below it that cooled, shrunk and over which powder was spread in a potentially thicker layer. However, despite this feature being easily discernable to the eye, and measurable in cross section, it did not appear distinctly in surface roughness measurements, nor in static mechanical testing (tensile and microhardness tests).
231 - Microstructural Tailoring of Additively Manufactured Duplex Stainless Steels Through Activated Shielding
Youssef Refaat Ali, The Pennsylvania State University-University Park
Maintaining a balanced ferrite/austenite microstructure in additively manufactured lean and standard duplex stainless steels in the as-deposited conditions is not easily achievable through changes in laser power and travel speed alone. Increasing nitrogen composition in these alloys by manipulating the composition of the powder feedstocks can promote the formation of austenite. Additions of nitrogen to the shielding gas can also manipulate the nitrogen composition and resulting alloy microstructures. A laser-based directed energy deposition process was used to fabricate lean (UNS32101) and standard (UNS S32205) duplex stainless steels with nitrogen shielding gas additions between 0% and 10%. These argon-nitrogen mixtures increased the nitrogen composition in the as-deposited material, and the austenite fractions from 35% to 55 %, with intragranular austenite morphologies being the most common. At the same time, the formation of intermetallic phases, such as sigma phase, was suppressed. Microhardness testing indicate comparable performance to those found in wrought alloys.
034 - Effect of Novel Nano-Boronated Alloy on the Densification, Surface Morphology, Hardness and Magnetic Properties of Sintered AISI630
Arun Chattopadhyay, Etimine USA Inc.
This paper investigates the effect of a novel nano-powder of (FeCoNi)70Ti10B20 alloy synthesized by mechanochemical method on the characteristics of sintered AISI630 steel powders. Boron migration from the nano-composite to the steel matrix during sintering process at 1330 °C seemingly changes densification, particle surface morphology, hardness and magnetic properties. The surface morphology of the nano-(FeCoNi)70Ti10B20 induced steel powder was studied by the high-resolution transmission electron microscopy (HRTEM). The phase identification and structural changes were followed using X-Ray diffractometry and Raman spectroscopy. The magnetic property of sintered powder was investigated using vibrating sample magnetometer (VSM).
195 - Additive Manufacturing of High Strength Niobium Alloys
J. Scott O'Dell, Plasma Processes, LLC
Niobium (Nb) alloys such as Nb-1Zr and C-103 have been used for various high temperature components due to their combination of good formability at room temperature and improved strength as compared to pure niobium. However at elevated temperatures, the strength of these alloys decrease significantly. Higher strength Nb alloys have been developed, but these alloys lack the formability of C-103 and Nb-1Zr. Recently, Additive Manufacture (AM) of Nb and C-103 has been demonstrated. However, AM of Nb and C-103 results in elongated, columnar grains, which reduce mechanical properties as compared to a cold worked material. Therefore, the potential exists to develop and fabricate a higher strength Nb alloy by taking advantage of the net-shape forming capability of AM to circumvent the lack of formability of these alloys using conventional processing. During this investigation, high strength Nb alloys based on solid solution and stable high temperature precipitation strengthening were evaluated. To produce the Nb alloy feedstock, an innovative Plasma Alloying and Spheroidization (PAS) technique was used that resulted in spherical, highly flowable powder, which is essential for AM processing. The PAS Nb alloys were then successfully AM processed using Electron Beam – Powder Bed Fusion (EB-PBF). Improvements in microstructure and mechanical properties as a result of the solid solution and precipitation strengthening alloy additions were observed, which resulted in tensile strengths that exceeded wrought C-103 with equivalent ductility. These results will be discussed in this paper.
SESSION T08 Tungsten Processing
056 - Enhanced Sintering of Tungsten
John Johnson, FAPMI, Novamet/Ultra Fine Specialty Products
Tungsten ingots are usually sintered to a closed pore condition and thermomechanically processed to full density. Processing net-shape tungsten parts to near full density is highly desirable for reducing costs and material usage but requires enhanced sintering methods. Densification of tungsten can be improved by using sub-micrometer or nanograined powders, by applying external pressure, or by adding small amounts of transition metals. Other methods that can potentially improve densification are application of current, application of electromagnetic radiation, or addition of small amounts of insoluble particles. Experimental data from these processes are used in a model for densification based on master sintering curve (MSC) concepts to assess their effectiveness for achieving sintered densities above 18.5 g/cm3.
080 - Dose Reduction and Performance Improvement at Different CT Application by 3D Screen Printing
Guido Stiebritz, H.C. Starck Hermsdorf GmbH
By using parts made by metal additive technologies, computed tomography (CT) scan units for medical as well as for nondestructive testing or luggage control units can be improved a lot. For example, the higher complexity in the collimators allows an improved noise reduction and results a reduction of the dose for the patient. This path forward requires high aspect ratios at very good wall quality. The examples will illustrate the advantages of the 3D screen printing technology in that area and possibilities will be reviewed how to combine with conventional manufacturing methods.
247 - Peeking into the black-box of tungsten carburization
Thomas Jewett, Global Tungsten and Powders
Production of tungsten carbide from tungsten metal powder via solid state carburization in graphite boats filled with a mixture of tungsten and carbon powders has been an industrial staple for decades. While various studies have established the transformation pathway and general reaction kinetics for the formation of tungsten carbide in laboratory scale samples, industrial production has essentially remained a black-box operation with only limited inputs with which to control the morphology, chemistry and quality of the final product. A recent investigation into heat transfer within a simulated industrial scale quantity of mix-milled powder has allowed for simulation of the heat flow within a boat of coarse tungsten metal, 20 microns, and carbon powders. Upon expanding the investigation to finer size powders, 3.5 microns, the presence of an exothermic reaction was revealed during the testing. The exothermic reaction was found to be sensitive to the tungsten metal powder size, the sample mass, and the powder preparation methods.
Special Interest Program Abstracts
SIP 3-1 Flow and Spreadability Characterization of Metal Powders I: Powder Spreadability
564 - Review of the ASTM CoE Program on Metal Powder Feedstock Characterization
Steven Hall, The Manufacturing Technology Centre (MTC)
Understanding how metal powder feedstock will perform in additive manufacturing (AM) processes, and its influence on the integrity of built components, is crucial for ensuring a successful manufacturing process. However, there are at present a number of gaps in feedstock characterization standards, many of which require R&D studies before appropriate standards can be developed and/or updated. To that end, the ASTM AM Center of Excellence (CoE) has funded two R&D projects led by MTC, to help develop knowledge in the topics of “Quality Assessment Guidelines for AM” and “Powder Spreadability Definition and Measurement Methodologies”. Both projects aim to understand what tests to perform to reliably measure flowability, that are most relevant for metal powder-bed AM processes. This presentation will summarize these activities, highlight the progress made, and indicate how the R&D will impact standards development.
570 - Comparing the Spreadability and Flowability of Recycled and Virgin 316L Stainless Steel Powders for Additive Manufacturing Applications Using a New Powder Spreadability Analyzer and the Revolution Powder Analyzer
Greg Martiska, Mercury Scientific Inc.
The spreadability and flowability of recycled and virgin 316L stainless steel powders manufactured for additive manufacturing applications are measured and compared for a range of layer thicknesses and different application conditions. Conditions include a range of spreading speeds, different spreader geometries, different powder build surfaces, a range of powder feeding geometries and spreader application pressures, and different environmental conditions. The powder spreadability analyzer used for the measurements is a new instrument commercially produced by Mercury Scientific Inc.. Powder flowability is assessed using the Revolution Powder Analyzer.
549 - A Prototype of a Standard Spreadability Tester for Additive Manufacturing
Justin Whiting, Georgetown University/National Institute of Standards and Technology
We describe a simple device called the Standard Spreadability Tester (SST). The idea behind the SST is that instead of trying to predict how a powder will spread using the powder’s intrinsic properties (e.g., particle size distribution (PSD), morphology, surface, and chemical makeup) or how it performs under some other stress conditions, we subject the powder directly to conditions of stress very similar to what it sees in a Powder Bed Fusion (PBF) machine. In brief, the SST provides a test method that is straightforward and can be run in a laboratory or commercial setting. In this work, we have described the design of the device and proved the concept by preliminary testing. The remaining potential improvements have been also discussed.