PowderMet          AMPM          Special Interest

049 - An Objective and Continuous Metric for Powder Spreadability
David Scannapieco, NSL Analytical Services

Powder flow and spreadability has been a continued area of research and uncertainty in the additive manufacturing (AM) community. Aspects and complexity of powder flow allude fixed, predictable models. Limited correlations to testing methods such as rotating drums, stirring in cups, powder size distributions, and powder morphology have been demonstrated in the past. ASTM and ISO recently released technical report ISO/ASTM TR 52952 which provides some understanding of the powder flow metric influence on spreadability. However, the study used qualitative metrics to determine powder spreadability, which is subjective and fails to account for all failure points in a powder layer. Powder layers cause AM parts to fail by wavey layers, lack of full coverage, and insufficient packing density. Powder spreadability is the final property that most directly defines success in AM. However, lack of methods for continuous metric of powder spreadability limits the ability to model and predict it outside of the AM machines. In order to develop quality and verification standards for powder spreadability, a continuous and easily measurable metric must be developed. This work will highlight a novel, continuous, and objective metric for powder spreadability. Some correlations with powder size, shape, flow metrics, and moisture content are discussed.

036 - AM Powder Standards: The Need to Adopt State-of-the-Art Characterization Methods
Aurélien Neveu, Granutools

The current standards rely on well-established methods allowing to evaluate independently either the intrinsic properties of the particles (e.g., particle size distribution, morphology, chemical composition) or the macroscopic manifestation of these properties (flowability, packing dynamics). However, the results obtained are strongly dependent on the measurement configuration and conditions. Moreover, the large number of methods described in the current standards prevents from providing comprehensive and universally applicable procedures to additive manufacturing end-users. This situation highlights a need to identify the relevant parameters to be used in metal powder characterization for additive manufacturing. More specifically, a clear link between powder properties and the relation with their performance in the process is still lacking.
During the last decade, improved powder characterization techniques have been developed to tackle the limitations of the standardized protocols. These new methods allow for gathering new insights into powder properties by providing new metrics and/or more repeatable and user-independent results. It is now essential to update the standards to have a wide adoption of these improved technique in the AM community. In this presentation, we will review the current standards applicable to AM powder and present the state-of-the-art powder characterization techniques and the kind of information that can be gathered by these methods.

111 - Effect of Adhesive and Cohesive Forces on Rheology of PM Formulations
Lydia Aguirre Perales, Rio Tinto Metal Powders

Particles in the micron or nanometer size ranges are called colloidal particles. Particles smaller than colloidal particles are governed by atomic and molecular forces. Particles greater are usually controlled by gravity. With colloidal particles, forces other than gravity dominate, such as van der Waals (vdW) forces and electrostatic forces. Metal powders are colloidal particles and can experience adhesion and cohesion caused by these forces. Adhesion describes the sticky interaction between a particle and a surface of a material and cohesion describes the interaction between particles of the same material. In powder metallurgy operations, adhesive and cohesive forces change the rheology of metal powders which can cause poor filling before compaction. Studying the causes behind these cohesive forces is therefore crucial in understanding powder flow. Reducing cohesive forces would allow the production of higher-quality pieces with metal powders by improving the die filling, and eventually reduce production times. Cohesive forces between metal powders are usually attributed to vdW forces, electrostatic forces and forces due to humidity (capillary forces, liquid bridges, H-bonds). Chemical composition, particle size and shape, and surface roughness all affect cohesion and adhesion phenomena. Environmental factors such as temperature and humidity can also play a large role. In the current study, common powder metallurgy base powders and additives are subjected to different interactions and their relationship to premix rheology is explained. 

124 - Consolidation of Chromium Components through Nanophase Separation Sintering
Michael Spencer, Veloxint, Inc.

Chromium components are strong and corrosion resistant. However, chromium alloys consolidate poorly and require the application of high pressures and temperatures. Through the process of nanophase separation sintering, Veloxint has made it possible to consolidate components in excess of 99% density without the need for pressure. These powders can be molded into near net shape and sintered to create parts with improved mechanical properties in part to Veloxint’s chromium alloy technology.

139 - Exploring the Role of Composition on the Properties of Additively Manufactured Corrosion Resistant Alloys
Todd Palmer, Penn State University

A range of solidification conditions are encountered in common nickel base and stainless steel corrosion resistant alloys across different additive manufacturing processes.  The resulting as deposited microstructures are characterized by elemental segregation that drives the formation of secondary phases not commonly observed in comparable wrought alloys.  Even though the compositions of the starting alloy powders fall within standard ranges, small differences in even minor alloying element compositions can further impact which phases form.  In common nickel base alloys, such as Inconel 625, a complex interplay between iron, silicon, titanium, and nitrogen, drive the precipitation of a range of nitride phases that impact mechanical and corrosion properties.  Different secondary phases are also observed in austenitic stainless steels fabricated using additive manufacturing processes, with 316L austenitic stainless steels being impacted by differences in oxygen, nitrogen, and manganese.  With oxygen contents on the order of approximately 0.1 mass fraction (%), the precipitation of spinel oxides during solidification is promoted.  Decreases in the manganese composition to a level on the order of 0.5 mass fraction (%) leads to the replacement of these spinel oxides with a-tridymite and Cr2N phases.  The emergence of these phases activates new fatigue failure mechanisms that vary with locations within the specimen and leads to a decrease in the strain-controlled fatigue life. 

100 - Metal Binder Jetting of Safety Critical Automotive Components
Mattia Forgiarini, Azoth

Metal binder jetting is a promising additive manufacturing process as it can form complex geometries out of powder metal without the use of direct heat input at high production rates and low manufacturing cost.
In this work, metal binder jetting is presented as a fabrication process for automotive vehicle components, specifically interior safety applications.
This component is a customer-facing automotive part requiring cosmetic surface finish and properties critical for passenger vehicle safety. This component is the first sinter-based additively manufactured safety critical part in a production vehicle. The development of additive manufacturing intended designs and post-processing approaches using metal binder jetting as a fabrication method were investigated and executed into production.
To validate the components, multiple material tests and application-specific tests were performed. Many factors had to be taken into consideration to match the level of standardization and quality control required for automotive production. These components have passed all quality requirements to achieve production part approval process (PPAP) and are installed in production vehicles.

 140 - Scaling Metal Additive: Bolstering your Value Chain
Chris Prue,  UPM Additive Solutions

As Additive Manufacturing continues to scale many are concerned over the costs of the machine and the powder. However, have you considered the build plates, re-coater blades, and outside machining services needed to keep the process running at a high level?  Do you have all the skills integrated to accept scaling your process? Case studies will highlight the importance of consumables management along with de-focusing on non-value added work to adopt metal additive and also allow it to grow.

005 - Tribological Evaluations of Additive Manufactured Heat Exchanger via Additive Manufacturing
Onyeka Franklin Ochonogor, Vaal University of Technology

Additive manufacturing (AM) is presently receiving attention which is expected to increase drastically due to its processing advantages over traditional manufacturing methods. However, there are limiting factors around optimization for surface quality, which is an indication to mechanical and tribological performance of engineered components.
This paper evaluates the tribological properties of additive manufactured heat exchanger where the anisotropic mechanical properties such as stiffness, yield stress or fracture properties and the effect of wear resistance and oxidation behavior of additive fabricated heat exchanger. Optimized processing techniques that have been employed in this regard will be critically reviewed which is also expected to give important information towards increasing the thermodynamic efficiency of heat-transfer mechanism of the fabricated component.

110 - LPBF Manufacturing of Traditionally High Reflectivity Metallic Material Using Non-atomized Powders
John Barnes, The Barnes Global Advisors

Atomized metal powders currently available for additive manufacturing (AM) pose challenges of cost, waste, storage, and handling-related safety hazards, thereby hindering the broader adoption of metal additive manufacturing into new industrial applications. In this work, a mechanical solid-state process is used to convert bar stock of copper and aluminum alloys into non-equiaxed, pore-free powder. This powder manufacturing approach, which is applicable to a wide variety of metal and polymers, was tested for feasibility using laser powder bed fusion (LPBF) AM. LPBF of high reflectivity materials such as Cu and Al alloys poses processing challenges of porosity and cracking. To address these challenges, a combination of physics-driven LPBF processing diagrams, melt pool simulations, beam path planning, and advanced material characterization equipment including X-ray computed tomography, in situ optical tomography, and in situ powder bed imaging were used in the process parameters development cycle. Our efforts to careful control of vaporization during LPBF are expected to lead to high density parts. A detailed case study on parameter optimization for high density and high surface roughness will be presented for a Cu14500 alloy. The study will also detail the heat treatments deployed to optimize the electrical conductivity properties of the Cu14500 material system. This work provides insights into the feasibility of adoption of environmentally- and economically-sustainable powders. 

019 - Investigation of Microstructural Alignment Utilizing Engineered Cooling during Additive Manufacturing of Powder-Based Alnico Magnets
Luke Gaydos, Iowa State University

Alnico is an anisotropic, rare-earth free, permanent magnet (PM) which maintains its saturation magnetization while at temperatures up to 550 °C but lacks the coercivity and energy product needed for a wide range of demanding applications. With an optimal set of processing and manufacturing techniques, alnico could replace Dy-free Nd-Fe-B magnets in certain applications if the microstructure is textured in a〈001〉direction. Additive manufacturing (AM) of near-net-shape magnets may provide such texture. To investigate the possibility, directed-energy deposition (DED) in conjunction with an actively cooled substrate was used to build samples with a compositionally modified, gas-atomized, alnico 8 alloy. The resulting samples were solutionized and quenched, followed by magnetic annealing and a heat treatment. Magnetic properties and microstructures are compared to previous work. Funded by KCNSC through Ames Lab contract no. DE-AC02-07CH11358. Honeywell Federal Manufacturing & Technologies, LLC operates the KCNSC for USDOE/NNSA under contract number DE-NA0002839.

022 - Additive Manufacturing of Steels for Tooling Applications
Zhuqing Wang, Kennametal Inc.

High carbon tool steels are commonly used for tool holders, tabs and dies, etc. for their favorable combination of toughness with satisfactory hardness, wear resistance, and high temperature strength. Additive manufacturing allows for the geometrical degree of freedom and it has become an attractive option to fabricate tools with complex shapes and intricate cooling channels. However, carbon tool steels made using laser powder bed fusion are susceptible to cracking due to the martensitic transformation and thermal stresses. Maraging steels, on the other hand, also feature high hardness and strength but are much easier to print due to low carbon content, so they can also be used for some tooling applications. This work will discuss the challenges and solutions in printing tool steels and maraging steels and compare microstructure and properties between them. This work will also show examples of innovative components enabled by using DFAM principles.

132 - Rapid Thin Wall Parameter Development for Corrosion Resistant Flow and Filtering Applications in Laser Powder Bed Fusion
Jake Jones, Penn United Technologies Inc.

The process uncertainties of Laser Powder Bed Fusion (L-PBF) often require an extensive development timeline to qualify parameters that produce stable and consistent geometry. In this work, an experimentally derived regression of dimensionless parameters is proposed for predicting single track wall thicknesses which can be adjusted for the characteristics of a desired alloy. The predictive capabilities of the model allow for informed parameter adjustments to control the nominal wall thickness of thin structures. The model is then implemented to produce a 316L filter component which is sectioned and measured for validation of this method.

117 - Laser Powder Bed Fusion of Pure Tantalum: Densification, Microstructure, and Mechanical Properties
Alfred T. Sidambe, University of Liverpool

Enhancing part quality and maintaining structural integrity, whilst reducing the production costs in laser powder bed fusion (LPBF), presents an opportunity for high-cost refractory metals such as pure tantalum. Tantalum is known for its exceptional corrosion resistance, high melting point, and biocompatibility which makes tantalum an ideal choice for ultra-high temperature applications in military, electronics, chemical processing and biomedical implants. This study analyses the densification, microstructure, and mechanical properties of LPBF tantalum. Light optical microscopy, scanning electron microscopy and tensile test results show that a laser powder bed fusion process energy of 163 J/mm3 is adequate to process tantalum and produce functional parts. The final density of the parts obtained from optical analysis is 99%. Analysis of the microstructure indicates that solidification occurs in a favored orientation, as a result of epitaxial growth of grains within the melt pool produced by the laser beam. Tensile tests of the as-printed tantalum LPBF samples, exhibit a strength of up to 632 MPa for specimens fabricated in the horizontal orientation and up to 834 MPa for vertical samples. The elongation obtained is up to 27% for horizontal samples and up to 26% for samples in the vertical orientation. The results of the mechanical properties are within the ASTM specifications, demonstrating that it is possible to overcome the barriers that affect the processing of tantalum in LPBF. This study makes a valuable contribution to the high-value manufacturing sectors in which tantalum is used during the LPBF process.

541 - Neighborhood 91 is a Production Ecosystem
John E. Barnes, The Barnes Global Advisors

Neighborhood 91 is many things.  Organized by the Allegheny County Airport Authority, Neighborhood 91 makes use of 195 acres of their over 8,000.  In the Pittsburgh region, all of the elements of the metal Additive Manufacturing (AM) supply chain exist but are not well connected, are fragmented, and not linked with workforce components.  A balance between technology and knowledge has always existed in manufacturing and is still true with AM.  We call this a "Tech-Know" relationship a cornerstone of our activities.  First, Neighborhood 91 is a production campus.  Second, it brings like-minded companies together in close proximity to trade with one another and thus creates an ecosystem, like Silicon Valley, where complex transactions occur and create a fabric.  Today, the first two buildings have been built and pads for building the next 5-7 buildings are prepared.  The scope of our campus is focused on the needs of advanced manufacturing with innovative solutions for aspects like power, industrial gas, and workforce.  Combined with the 200-acre development at Mill 19 for development, Pittsburgh has 400 acres dedicated to the next century of manufacturing.  In this presentation, The Barnes Global Advisors (TBGA), the strategic partner, will highlight the mission, the progress, and the future.