PowderMet          AMPM          Special Interest

142-R - Microstructure Characterization of High-Density Sinter Hardened Steel
Amber Tims, PMT, North American Höganäs Co.

Sinter hardening is a process that uses accelerated cooling following sintering in combination with required alloying elements and contents to achieve a desired metallurgical matrix for powder metallurgy (PM) components. Sinter hardened materials normally consist of prealloyed low-alloy steel powder admixed with graphite and copper.  Understanding the responses of martensitic phase formation with different graphite and copper additions is crucial to the selection of suitable sinter hardening material compositions, especially when the material is sintered at different densities. Since sinter hardening occurs during rapid cooling, the density of components plays an important role in achieving desired microstructures. Parts at higher density contains more heat energy that could affect the cooling rate compared to the one at lower density. In this paper, a series of studies was performed to investigate the sinter hardening responses of a FLC-4608 sinter hardened material compacted at different densities with various graphite and copper additions.  

129 - Consolidation of Mg-Ni-Nb2O5 Powder Mixtures Through Severe Plastic Deformation Using HPT
Martin Fibela Esparza, CINVESTAV

There exists interest on severe plastic deformation (SPD) techniques to produce ultrafine grain materials. SPD techniques are usually applied to monolithic materials, while their application to powders has received less attention. In this work, Mg-5Ni-2Nb2O5 powders were subjected to high pressure torsion to improve their hydrogen storage properties. Consolidated disks (10 mm diameter, 1 mm thickness) were produced by applying 1 to 30 revolutions at room temperature and under 3 or 5 GPa. These materials have been characterized by optical and electron microscopy, density measurements and microhardness testing. The grain size after processing at 5 GPa is about 345 nm after 1 rev and 150 nm after 20 revolutions. Porosities were practically eliminated after only 1 rev, with density values becoming constant after 5 rev. Microhardness measurements increased from initially ~ 40 Hv to up to 65 ~ 95 HV after 30 revolutions, depending of the applied pressure.

161 - Mn Alloyed Steels with TRIP Behaviour for PM Gears Applications
Laura Galvao Barbosa, MIBA Sinter Group

Manganese is a very attractive alloying element but higher contents of Mn are rarely used in the PM-Industry due to its high vapour pressure which leads to Mn-loss during the sintering process. Nevertheless, high alloyed Mn-steels that show work hardening behaviour are promising on metallurgy precision parts that are surface densified locally, such as PM gears. The possibility to combine densification with local hardening – using the behaviour caused by TRIP/TWIP effects – makes such materials interesting. In the present study, Fe-Mn-C alloys were sintered and surface densified by cold rolling, varying the number of rotation and total infeed in each sample. The aim was to analyse deformability, depth of densification, break/crack behaviour and hardness resulting from the austenite-martensite volume transformation in these different process conditions. It can be shown that hardness can be increased for all samples when compared by using the TRIP effect and it was possible to see a microhardness profile comparable to conventional heat treatment.

123 - Properties of Age-Hardened Cu-Ni-Si Powdered Metal Parts from Blended Powders
Daudi Waryoba, Penn State University DuBois

CuNiSi is an ideal material to use to replace more toxic alloys such as copper beryllium. Having a combination of good electrical conductivity, thermal conductivity, and high strength, this alloy can be used in a multitude of applications. Some of these applications include valve stems, connectors, fuse clips, and contact springs. The alloys are strengthened by precipitation through age-hardening process. They are commonly manufactured as wrought products via thermo-mechanical routes such as hot and cold rolling into final products. This study investigates the use of powder metallurgy for the fabrication of these alloys. Three blended powders were used, Cu-Ni-Si, Cu-Ni-Si-Al, and Cu-Ni-Si-Mg.  The powders were compacted to a density of 8.1 g/cm3, sintered at 820 °C for 10 min in a 93%N2 7%H2 atmosphere. Age hardening was performed at 450 °C for 1 – 2 hrs. The results show that the transverse rupture strength of age-hardened parts doubled compared to as-sintered parts. Other properties such as porosity and dimensional changes will also be reported.

101 - Effect of Processing Parameters on the Electrical and Thermal Conductivity of Copper Powders
Nicholas Murphy, Kymera International

Copper has been and continues to be ubiquitously used for its high electrical and thermal conductivity. What follows is a review of the conductive properties of a variety of types of copper powder. We attempted to optimize conductivity in test powders by altering process parameters, and then compared performance of the different materials. Several traditional press and sinter varieties of copper powder were studied, but some samples were cold sprayed or 3D printed. Further, we attempted to determine relationships between conductivity and the physical and process parameters that were employed.

048 -Structure-Property Relationships in Hot Isostatic Pressed Copper by LPBF
Rachel Paddock, University of Texas at Austin

Laser powder bed fusion (LPBF) additive manufacturing (AM) of copper and copper-alloys is difficult due to their high reflectivity and thermal conductivity. Hot isostatic pressing (HIP) can potentially reduce internal porosity and increase properties of LPBF copper samples. This research explores the mechanical, thermal, and electrical properties of LPBF copper before and after HIP. Tensile properties, density, electrical resistivity, and thermal conductivity of samples are correlated to their structures measured via X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive Spectroscopy (EDS), X-section metallography, and X-ray micro computed tomography (uCT). Further investigation into the samples is carried out by preforming inductively coupled plasma (ICP) elemental analysis and regular heat treatment. Based on the results of these test, explanations are given for discrepancies and suggestions for further prints. 

061 - Development of Nickel-Free Stainless Steel and 2507 Duplex Steel for the Binder-Jet Process
Kerri Horvay, Hoeganaes Corporation

Nickel containing stainless steels can be problematic in applications that include skin contact due to potential allergic reactions. Developing a material that is suitable for applications where nickel allergies may be an issue for use in the binder-jet process is of interest. For this study, a nickel-free stainless steel, 316L stainless steel, and 2507 duplex steel were chosen to evaluate the material properties of binder-jet test specimens due to their varying levels of nickel concentration. Mechanical properties will be evaluated in the sintered and heat treated condition. Microstructures and porosity will be discussed in relation to the build parameters and mechanical properties. Corrosion resistance will also be investigated and correlated to the nickel concentration in the alloys.  

130 - Metallurgical Properties of Binder Jet Processed Stainless Steels
James McKinnell, HP Inc.

Binder Jet technology is a 3D printing technology which produces metal parts for mass production.  A significant consideration for adoption of this technology is the quality of the metal parts.  We report the metallurgical and mechanical properties of SS316L and SS17-4PH parts made with Metal Jet.  Properties of SS17-4PH in both the sintered and H900 states are reported. 

041 - Influence of Chamber Gas and Feedstock on Microstructure and Corrosion Resistance of Additively Manufactured 316L Stainless Steel
Rajeev Gupta

Selective laser melting (SLM), an additive manufacturing (AM) technology, has been widely employed to print metal components. The components produced by SLM are often reported to depend on the characteristics of the feedstock powder and SLM process parameters like chamber gas. During SLM, the interaction between the laser beam and the powder bed causes a significant temperature rise promoting stable oxide formation. Such oxide formation is undesirable and is minimized by flushing suitable inert gases into the SLM chamber. Argon and nitrogen gases are mostly used for this purpose. From a commercial perspective, the high purity Argon is expensive than Nitrogen. If nitrogen can suffice the need during SLM, replacing Nitrogen gases with high purity Argon would provide commercial benefits. Moreover, nitrogen may have its own advantages for materials like stainless steel. This research investigated the properties of 316L components selectively laser melted in Nitrogen and Argon environments using a feedstock that was modified by oxides and nitrides. X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy were used to study the effect of the chamber gas and additives on the microstructure. Cyclic potentiodynamic polarization tests and surface analysis after corrosion tests were used to study the corrosion performance. The role of the additives and chamber gas on the microstructure and corrosion performance of selective laser melted 316L stainless steel has been discussed. 

043 - Moisture in AM Powders
Louis-Philippe Lefebvre, National Research Council Canada

Moisture may affect the properties of powders and additive manufacturing (AM) process reliability, stability and productivity. Despite AM powder feedstocks are generally produced and handled with care under controlled conditions, moisture cannot be completely avoided and a small amount is adsorbed on the surface of most powders. While it is recognised that the effect of moisture on the properties and behaviour of the powders depend on surface composition and area, it is not clear how surface composition influences the interaction with water and the kinetics of water adsorption and desorption.  This question is important to address as it will influences the guidelines for the monitoring of moisture and the determination of limits acceptable for specific AM feedstocks. This paper presents the moisture content in different as-received powders and their response to humidity and drying treatments.  The results indicated that the moisture content varies typically between 15 and 250 ppm depending on the nature of the powders.  Drying at 260°C under vacuum allow to reduce the amount of moisture but is not sufficient to remove all water from the surface of some powders.  Exposure to humid environment (168 h at 50 °C and 80 %RH) leads to an increase of the moisture in most powders.  Drying and humidifying may also cause the oxidation of the surface of some powders. The results indicate that the amount of moisture, adsorption/desorption and reactivity depends greatly on the nature of the powders. 

066 - Hot Static Degassing of Metal Powders for Laser Powder Bed Fusion Applications.
James Sears, Amaero Additive Manufacturing

It has long been known that moisture contaminates the surface of metal powders usually on the nanoscale The smaller diameter powders used in Laser Powder Bed Fusion (LPBF) have more surface area compared to larger powder and therefore are more susceptible to moisture contamination. Without removal this moisture content, issues with powder spreading and for some materials (e.g., aluminum alloys) porosity in the final product can arise. Therefore, for manufacturing high quality parts through the LPBF process, extremely dry metal powder is required. One method for achieving dry powder is using Hot Static Degassing (HSD) that involves applying enough heat to the metal powder to liberate water molecules from the surface of the powder, and then their removal in a vacuum. Using a custom-built HSD system, aluminum alloy powder reached values of less than 0.5% relative humidity. Material results from LPBF fabrication of Al10SiMg will also be presented.

121-R - Improving Surface Quality and Geometric Fidelity of Water Atomized Pure Iron in Laser Powder Bed Fusion
Allan David Rogalsky, MSAM—University of Waterloos

Laser powder bed fusion (LPBF) technology adoption is strongly driven by the ability to produce parts with a high degree of geometric complexity. Such components often require a threshold surface quality and geometric fidelity to avoid excessive post processing and maintain competitive advantage.  Achieving these consistently is an active area of research in the field of additive manufacturing. This study proposes a combined physics-based modeling and empirical strategy to refine water atomized pure iron surfaces in close contact with the powder bed. Using parameters such as power, effective velocity, and hatch spacing control can be exercised over heat dissipation, melt pool geometry and melt pool stitching resulting in meaningful variation in part properties.  Control of heat dissipation was important for artifact feature resolution and geometric fidelity.  Surface roughness achieved range from Ra = 24 µm on vertical surfaces to Ra = 59 µm for unsupported surfaces at 30° from horizontal.  

136 - Modelling of Sintering and Deformation of Binder Jetted Parts
Pavan Suri, HP Inc.

Increased design freedom of AM technology enhances the importance of modelling of the printing and sintering process to understand how the part evolves and deforms during processing. The presentation provides a broad review of available tools and efforts to leverage and develop methodologies to make the Binder Jet Technology effective and successful.

089 - Discrete Element Modeling of Charpy Impact Test of Additively Manufactured 316L Stainless Steel
Tejesh Dube, Indiana University—Purdue University Indianapolis

In this study, the discrete element method (DEM) is used to simulate the Charpy impact test of additively manufactured or 3D printed 316L stainless steel. First, the DEM model is calibrated using quasi-static uniaxial tension and uniaxial compression tests to derive the parameters in the DEM bond model. Then the Charpy impact test model will be built, and the impact test will be simulated. In parallel to the model, Charpy impact test experiments of 3D printed 316L stainless steel will be performed. The experimental data will be compared against the modeling predictions.

223 - PM and the Mechanical Diode Clutch in Automatic Transmissions
Jeff Prout, Amsted Automotive

Automatic transmissions require various types of clutches as torque carrying shifting elements. These clutches have become more sophisticated over time resulting in improved efficiency, capacity, and functionality, while reducing in size and weight. The Mechanical Diode Clutch has been enabled to be a leader in these areas by PM technology. This presentation will review the basic function of automatic transmissions and it’s clutches, and the importance of PM in Mechanical Diode technology.

224 - PM Clutching Applications in Electrified Propulsion Systems
Jeff Prout, Amsted Automotive

A primary requirement of the next generation of electric vehicles is to increase battery range. Engineers are focused on various architectures that include multi-motor, multi-speed and multi-axle drive systems to achieve efficiency goals. The architecture developed is largely influenced by the vehicle type (passenger, commercial, industrial). The interaction of these systems is driving complexity into the hardware layout and the controls. There is a need to provide connection and shifting points between them with seamless transitions. This presentation will introduce these connection and shifting element locations, why mechanical clutches are suited for these needs, and the opportunities for PM clutching components within them.

225 - Confronting the Challenges of Predicting PM Performance in Powertrain Applications
George Coppens, Amsted Automotive

The need for PM material properties that are representative of manufactured parts and provide the information necessary to predict performance is greater than ever. Companies are increasingly relying on computer-aided engineering (CAE) tools to predict component and assembly performance due to shortened development cycles and to eliminate the costly testing of many design iterations. The long lead times of PM parts requires designs to be validated virtually to meet program deadlines and to be awarded business. Accurate analysis of PM components requires material data that captures the manufacturing methods, porosity, strength, plasticity, static and fatigue life. Validated prediction tools and methodologies for using the tools and evaluating results are also needed. This presentation will review the work being done to improve predictive capabilities of PM.