PowderMet          AMPM          Special Interest

047 - Wear Evaluation of Cemented Tungsten Carbide with Nanocrystalline Fe-Ni-Zr Binder
Sean Fudger, U.S. Army Research Laboratory

Cemented tungsten carbide (WC) is a traditional machine and cutting tool material due to the extreme hardness and high modulus provided by the WC phase combined with plasticity and resulting toughness contributed by the cobalt (Co) binder. Due to the health hazards and supply chain concerns associated with Co, there exists a need to replace the binder material while maintaining the mechanical performance in these systems. Nanostructured Fe-Ni-Zr is evaluated as a plausible binder replacement to Co since it doesn't exhibit these concerns. A series of wear tests are performed to compare the performance of the cemented WC with novel Fe-Ni-Zr binder compared to that of traditional WC-Co material. Further, machine learning (ML) is utilized to help guide the material development process - particularly focusing on using computational techniques to explore complex multifactorial experiments in addition to data collection and analysis.

025 - Introducing the High Entropy Concept into Cemented Carbides
Johannes Pötschke, Fraunhofer IKTS

Traditional cemented carbides are based on tungsten carbide (WC) as a hard phase and cobalt (Co) as metal binder phase. Due to issues regarding health, the safety in supply, and ethical sourcing of both W and Co, alternative compositions are of increasing interest. Since its introduction the high entropy concept has been applied to many areas in material development: upon mixing five or more constituents in equal amounts to form a single phase, a high state of disorder is created which can lead to unique properties of the novel material. This concept is now applied to novel high entropy carbide (HEC) hard phases and high entropy alloy (HEA) binder phases in cemented carbides. Different routes for producing HECs with different compositions were investigated and feasibility studies with conventional binder metals such as Co, Ni or Fe-Ni were carried out. In addition, HEAs based on Mn, Co, Fe, Ni, and Cu were studied in cemented carbides with TiCN and WC as hard phases. Furthermore, trials with compositions combining HEC and HEA were successfully carried out. The resulting double high entropy based cemented carbide consists in total of 10 metallic elements plus C but comprises just one hard and one binder phase.

035 - Effect of Prime Materials and Process on Mo-Containing Tungsten Heavy Alloys for Die Casting Application
Caleb Glotfelty, Mi-Tech Tungsten Metals LLC

Mo is used as an alloying element in tungsten heavy alloys, particularly for the mechanical enhancement of parts in contact with liquid metal. These alloys are obtained using powder metallurgy and liquid-solid sintering. The interaction between each individual element at powder state as the Mo concentration itself might have consequences on product final properties, either mechanical, impact resistance or microstructure. For an optimized product, keeping those parameters as constant as possible is essential for product improvement. 

068 - Microstructure and Mechanical Properties of Dual Phase Steel Produced by LPBF
Kerri Horvay, Hoeganaes Corporation

As additive manufacturing continues to gain traction in automotive, however in industrial applications more development work is needed to expand the range of material possibilities. Dual phase steels are widely used in the automotive industry due to their combination of high strength and good formability. Intercritical annealing heat treatments are used to optimize the mechanical performance of the alloy by producing a two-phase microstructure consisting of islands of hard martensite and a soft ferrite matrix. By using post-processing heat treatments the range of the mechanical properties achievable provides greater flexibility to the end user by allowing one material to be utilized across different applications. DP600, a popular grade used for various automotive parts, was chosen for this study to investigate the mechanical properties and microstructure of components manufactured by laser powder bed fusion (LPBF). Charpy impact testing is used to evaluate the impact energy of the printed dual phase steel. The relationship between the impact energy and the microstructure developed by different heat treatments is examined.

094 - Impact Resistance of FSLA Steel Produced by Laser Powder Bed Fusion
Thomas Murphy, FAPMI, Hoeganaes Corporation

Dual-phase steels have been used by the automotive industry due to their high energy absorption during crash events. The locations on the automotive chassis in which the alloys can be utilized are a function of how much energy will be absorbed during impact (i.e. side members or pillar reinforcements). A dual-phase alloy called free-sintering low-alloy (FSLA), was designed and implemented for use with the additive manufacturing methods of both metal binder jet printing and laser powder bed fusion to expand the use of the alloy in these applications. Prior papers have discussed the development of a wide range heat treatments and the resulting microstructures for the alloy, that led to a variety of mechanical properties. It was shown that the microstructure can be altered from predominantly ferrite to that consisting of a high percentage of bainite and/or martensite. In this paper the impact energy of the FSLA is examined as a function of the microstructure developed during heat treatment. Fracture surfaces, transformation product volume and size, and micro-indentation hardness of the various phases will be related to the impact energy for the various heat treatments. From this information, recommendations for applications for the various heat treatments will be made.

085 - New Rotating Drum Rheometer Measurements to Identify the Source of Flow Problems in AM Powders
Gregory Martiska, Mercury Scientific Inc.

Rotating drum rheometers are widely used in the powder AM field to characterize powder flow properties. These measurements identify if powders will not perform well in printers and if the flow properties are changing with use. However, the measurements do not identify the reasons the powders are not performing well or why the flow properties are changing. This paper presents new measurements that are made in a rotating drum rheometer to identify the sources of problems with flow properties.

084 - A New Sensor to Measure Powder Layer Thickness, Powder Density, and Layer Uniformity in a Spread Powder Layer
Gregory Martiska, Mercury Scientific Inc.

Powders are spread in thin layers by various techniques in AM printers. The thickness, density, and uniformity of the spread powder layer impact the quality of the printed parts but are difficult to measure. Powder layers are only twenty to two hundred micrometers thick making measurements of thickness and density difficult, especially over a powder bed. This paper presents a new sensor and method to measure powder layer thickness, density, and changes in both parameters over a spread powder bed.

141 - Mechanical Chemical Bonding Technique for Modification and Coating of Metal Powders
Philip Mallory,  Vulcan Additives

Additive Manufacturing (AM) has become popular for commercial applications where high-performance parts can now be created, tested, and modified more efficiently thus expediting the design process. Because of its relatively easy access today a lot of research and improvements are coming out yearly for improved AM machines and the material used. In this research, a method of modifying as-received commercial gas-atomized metal powders used in AM has been developed using Mechanical Chemical Bonding (MCB) methodology which uses high rotational blades to create an environment where it increases the particle-on-particle interaction. During this high energetic process all irregular shaped particles, with satellite surface agglomeration, were shaped to near spherical geometry, while the internal gas pores are also eliminated, thus obtaining denser particles. Packing density and flowability of the particles before and after MCB processing were carried out by a flowmeter machine. Stainless Steel 316 and Inconel 718 powders were used in this research in the size ranges of 15-53 µm and 45-106 µm. Results showed that both the packing density and flowability increased by about 30%. This new MCB-processing method can make the powders with higher density, narrower size range, smoother surface morphology, and better flowability and packaging density; therefore, produce better structural parts (i.e. less internal defects and stronger mechanical properties) by AM. This process also sees promise in using water atomized materials as well because preliminary results show improved particle shape morphology and circular shapes starting to develop.   Furthermore, the MCB technique was also found as a very efficient method of coating minor addition of strengthening phases to the as-received gas atomized powders. Using MCB method, Oxide Dispersion-Strengthened (ODS) IN718 powders, i.e. uniform coating of various wt% Yttria on all surfaces of the 718 powders have been successfully fabricated. Preliminary tensile testing of AM-printed ODS IN718 alloys at 1050 C showed an increase in tensile strength compared to the AM-printed IN718. Other coating examples completed were with Radar Absorption Materials and by changing the material of what was being coated on the surface of the iron particle different absorption rates were observed. This could allow for increased radar absorption on multiple bandwidths or even mimicking of of other known radar sources. Lastly, the MCB method also appears to be a very effective method of recycling used AMed powders. Various post printed powders show concerning characteristics of damaged and irregular shaped powders due to laser power sintering during printing. After MCB re-processing the leftover AMed powders results show cleaned up powders with many of troubling powder properties being negated. Flowability and packing density of these MCB recycled powders also show improvements, which provide potential pathway for applications to downstream industries, such that sustainability and significantly reduced carbon footprint can be realized.

109 - Overcoming Part Shrinkage and Enhancing Yield Strength in Binder-Based 3D Printing of SS316L via Sub-Micron Metal Material Jetting
Buhari Ibrahim, University of Michigan

Metal binder jet (MBJ) 3D printing of metals and ceramics is an attractive additive manufacturing (AM) method for high volume production. However, the widespread use of MBJ been stymied by longstanding challenges in controlling final part shrinkage and porosity. We leveraged novel metal material jetting (MMJ) of sub-micron powders to overcome these challenges in binder-based AM. Stainless steel 316L cubes fabricated by MMJ were subjected to dilatometry under a representative sintering cycle and follow-on correlative characterization of microstructure, porosity, and mechanical behavior. Compared to MBJ, MMJ samples possess 80% reduced part shrinkage and 51% increased yield strength due to unique processing conditions that engender fine microstructures and low incident porosity. The specific mechanisms behind enhanced properties are discussed and elucidated using analytical modeling. Overall, these outstanding properties of MMJ SS316L highlight the strong potential for this AM method is multiple sectors.

134 - Fatigue Characterization of Plasma Atomized Ti-6Al-4V Produced by Laser Powder Bed Fusion Process
Mahdi Habibnejad-korayem, GE Additive

Laser powder bed fusion is a fast-developing metal additive manufacturing process which has attracted considerable attention in the aerospace and biomedical industries to manufacture Ti-6Al-4V material. Among all factors impacting the fatigue performance of LPBF Ti-6Al-4V parts, feedstock characteristics plays the most critical roles. In response to this challenge, this study endeavors to explore fatigue data collected from LPBF processed Ti-6Al-4V coupons printed using critical feedstock parameters e.g particle size distribution, reused powders, and oxygen content. The effect of Ti-6Al-4V feedstock parameters is primarily linked to the fatigue properties highlighting microstructure, defects, and failure mechanisms in the as-fabricated, stress released, heat treated and HIPed conditions. Results are subsequently compared to conventionally manufactured Ti-6Al-4V through casting, welding, extrusion. It is shown that fatigue performances highly depend on the feedstock parameters, but these effects are different, depending on the loading domains, high cycle fatigue and low cycle fatigue.

059 - Role of Manganese Composition on the Strain-Controlled Fatigue Life in Additively Manufactured 316L Austenitic Stainless Steel
Ian Wietecha-Reiman, Penn State University

Manganese compositions in additively manufactured 316L stainless steel typically fall in a range between 1 and 2 wt.%, which promotes the precipitation of spinel-based oxides during solidification. When the manganese composition is on the order of 0.5 wt.%, however, a-tridymite and Cr2N phases form along grain boundaries in the interior and contour regions of the specimens, respectively. The presence of these phases activated new fatigue failure mechanisms and led to a decrease in the strain-controlled fatigue life in the absence of process defects. In the fine grain structures present within the contour passes at the sample edges, intergranular failures were primarily initiated along austenite grain boundaries which were populated with micro- and nano-sized Cr2N and Mn-bearing spinel oxide phases. Decreases in the build angle increased the size of this contour region, leading to an increase in the amount of brittle intergranular failure and a corresponding decrease in fatigue lives. A coarse grain structure was observed when moving into the interior of the sample, where the Cr2N phase disappeared, and the grain boundaries were then populated predominantly with nanosized monoclinic α-tridymite and spinel phases, leading to brittle cleavage fracture at selected locations during crack propagation. 

042 - Comparison Analysis of Heat Treated LPBF Ti-6Al-4V and Wrought Fabricated Titanium
Luis Márquez, University of Texas at El Paso

Additive manufacturing of Ti-6Al-4V alloy through the process of laser powder bed fusion allows the production of complicated topological elements, making it a viable alternative to overcome the limitations of conventional manufacturing processes. To advance further incorporation of this process into the industry, it is necessary to verify that the material meets the demanding mechanical requirements defined by each sector. Therefore, it is required to determine the most adequate heat treatments for optimization of mechanical properties of this material. This investigation collects the results of a comparative analysis of post-process heat treatment of LPBF fabricated Ti-6Al-4V alloy with respect to wrought fabricated Ti-6Al-4V. Heat treatment in this study consists of standard hot isostatic pressing at 900 °C and 100Mpa with a 2hr dwell time, it was applied to 10 LPBF and 10 wrought fabricated samples. This resulted in 3 specimen variants: HIP LPBF, HIP wrought and as-purchased wrought. After conducting tensile and high cycle uniaxial fatigue tests, three performance of mechanical properties and stress-strain curves were analyzed for comparison between variants. Examination of microstructure was performed using optical microscopy on the cross section of polished pieces to assess whether the microstructure would further improve or remain unchanged, comparison and results were presented. 

060 - Developing Statistical Tools to Analyze Historical Fatigue Data in Additively Manufactured Alloys
Ian Wietecha-Reiman, Penn State University

The development of robust fatigue property data sets for additively manufactured 316L austenitic stainless steels is hindered by the small sample sizes, inconsistent reporting of material properties and processing conditions, and differences in testing procedures for current sources of testing data. By applying standardization and categorization protocols to account for these shortcomings, historical data sets were aggregated into a single large data set and analyzed in greater detail, providing new levels of insight into the fatigue behavior of additively manufactured materials. Using this single aggregated data set, scatter was quantified using an eigenvalue analysis, and a multi-variable statistical model for predicting the mean fatigue life was developed. Two distinct trends in behavior were identified using this analysis and attributed to the differing roles of microstructure and defects on the resulting fatigue lives across different equivalent stress amplitude ranges. Historical data is also used to improve precision of secondary models which incorporate fractographic measurements. Complex relationships which isolate the effect of porosity can be obtained to account for features such as circularity and debits for multiple crack initiation sites.

569 - SMC material selection for EV applications
Fabrice Bernier, FAPMI, National Research Council Canada

570 - Coated Iron Powder in Soft Magnetic Applications, Challenges, and Benefits
Kalathur Narasimhan, FAPMI, P2P Technologies

Coated iron powder for soft magnetic applications was developed in 1989-90 by Hoeganaes Corporation. The availability of pure atomized iron powder and higher density processes made the coated iron powder technology attractive for replacing lamination steels in some applications. Minimization of eddy currents in AC applications was achieved very effectively. However, larger coercive force in compacted coated powder compared to lamination steels produces higher hysteresis losses. Additionally coating results in air gap between iron powder particles which leads to lower permeability. This presentation discusses benefits of coated powder technology and 3D printing of soft magnetic materials.

571 - Permanent Magnets for EV Applications : Opportunities for the PM industry
Fabrice Bernier, FAPMI, National Research Council Canada