PowderMet          AMPM          Special Interest

032 - Development of a New Generation of Machining Additives that Optimizes Machinability and Mechanical Properties of Powder Metallurgy Components
Carl Blais, Laval University

Machinability of PM steel components is significantly lower than that of wrought steels due to the presence of residual porosity and the heterogeneity of their microstructure. Machinability issues, constitute a significant portion of the overall production costs of PM steel parts. The most popular strategy for improving their machinability involves admixing a chemical compound, such as MnS, MoS2 or BN-h, to the base powder. These machinability enhancers improve the machining behavior of PM steels by decreasing the cutting forces involved with chip formation and by lubricating the surface of the cutting tool, which in return reduce both flank wear and crater wear. This presentation highlights of a novel approach for developing machinability enhancers engineered to maximize machinability of PM without affecting mechanical properties nor corrosion resistance. Comparison with commercial machining additives is presented in terms of both machinability and mechanical properties.

044 - New Machinability Enhancing Additive for PM Steels
Carl Blais, Laval University

Despite the popularity of the powder metallurgy (PM) process for manufacturing near net shape components, a significant number of PM parts requires machining operations for geometrical conformance. However, the presence of porosity in the typical microstructure of PM parts greatly reduces their machining behaviour, thereby requiring the use of additives to improve it. The ideal machinability enhancing additive would be one that, on top of considerably increasing machinability, is chemically neutral, cost-effective, and has no detrimental effect on mechanical properties. Based on these criteria, work was carried out to develop a novel chemical compound that suites these requirements. The performances of this new material were characterized in terms of machinability, mechanical properties, and corrosion resistance and compared with the properties of the samples containing different commercially available additives. The results confirm the high effectiveness of the new additive to increase the machinability of PM steel parts without affecting corrosion resistance nor mechanical properties.

031 - Development of New Additive Systems for the Machining of Highly-Alloyed PM Steels
Mark J Dougan, AMES S.A.

Although press-and-sinter is considered to be a net-shape process, a significant proportion of parts require finish machining operations, either to reach tolerances or forms not directly achievable via uniaxial compaction. Such operations raise part cost, and hence improvements in machinability are sought to maximise productivity and cutting-tool life. MnS is routinely added to PM steels to facilitate machining, but has disadvantages including increased susceptibility to corrosion,  furnace damage, and limited effectiveness in highly-alloyed or heat treated steels. This paper presents a study of the effect of some new additives and combinations on the drilling and turning of highly-alloyed PM steel in comparison with both MnS and a commercial premix with machinability enhancers. On the basis of laboratory testing one additive system was selected for industrial production trials in which improved performance was demonstrated.

145 - Calcium Melt Delivery for Centrifugal, Close Coupled, and Free Fall Gas Atomization Processes for Production of Calcium Powders
Trevor Riedemann, Ames Laboratory

Aluminum/Calcium composite conductors as a candidate for overhead power transmission have been demonstrated on a laboratory scale. In order to provide feedstock powder for the project and to demonstrate that atomization of pure calcium metal is feasible, centrifugal, close coupled and free-fall methods have been applied.  The practical aspect of calcium powder production is the delivery of the calcium melt on, or into, the atomization disc or die. Discussion of developments for the melting and melt feeding system configurations for each method will be discussed.   This work has been supported by US-DOE-OE through Ames lab contract DE-AC02-07CH11358.

153 - Influence of Impurities in Gas Atomized Aluminum Powder on Strength and Electrical Conductivity of Deformation Processed Wires for Metal-Metal Composites
Dustin Hickman, Iowa State University

The electrical and mechanical properties of heavily deformed pure Al wire at different levels of purity are well established for Al ingot, as a starting material. However, new research is underway utilizing Al-matrix bi-metallic (Al/Ca) metal-metal composites (MMCs) for increased strength and electrical conductivity that has a matrix phase  made from Al powders. However, there is a modicum of material property data for wires made from Al metal powders with differing levels of purity for after consolidation and deformation to final diameter. Thus, this research explores the microstructure evolution and related properties of Al metal powder compared to ingot Al; of varying impurity constituents: iron, silicon, and oxides. The wires have sustained axisymmetric deformation through warm indirect extrusion and subsequent wire drawing to varying levels of deformation. Support from USDOE-Office of Electricity through Ames Laboratory under contract no. DE-AC02-07CH11358.

117-R - High Temperature Mechanical Properties of Gamma-TiAl Fabricated via Electron Beam Melting Additive Manufacturing
Patxi Fernandez-Zelaia, Oak Ridge National Laboratory

Titanium aluminides offer excellent high temperature specific strength however have been traditionally challenging to manufacturing. Recent advances in additive manufacturing (AM) have enabled successful processing of this material system via electron beam melting (EBM). However, limited work is available in the existing literature focusing on high temperature creep behavior of additively manufacturing TiAl. In this work we present recent results on the time-dependent behavior of EBM AM TiAl in both the as-fabricated and heat treated states. The structure-property relationships are discussed as well as implications of the results on applications for elevated temperature service conditions.

118 - Processing of MoTiC Alloys Through Electron Beam Melting
Michael Kirka, Oak Ridge National Laboratory

The processing of refractory metals via additive manufacturing (AM) presents an opportunity to significantly open the geometry beyond what has been capable through conventional techniques for refractory metals. Among the key challenges in processing refractory metals such as pure molybdenum and tungsten through AM is the ability to fabricate these materials in high quality, fully dense, and crack free forms. Much of the literature has reported on the processing tungsten and molybdenum through selective laser melting and electron beam melting, however, the hypothesis for the presence of cracking has been attributed to a number of items including the presence of absorbed oxygen in the feedstock powder. Further, studies have indicated the ability to process these materials in high quality, however, the presence or limits on allowable oxygen content in the feedstock have not been significantly investigated. Here we will report on how the accumulation of oxygen through controlled means degrades the processing of molybdenum and/or tungsten when utilizing optimized processing parameters for producing high quality material through electron beam melting. Through this work, insight in the impact of absorbed oxygen to defects such as cracking will be discussed.  

113 - Elevated Temperature Mechanical Properties of Additively Manufactured Refractory Metals
Christopher Ledford, Oak Ridge National Laboratory

Refractory metals exhibit desirable high melting temperatures but are challenging to process via traditional routes. Due to the ability to impose high preheat conditions, thereby mitigating against thermal stresses, electron beam melting (EBM) additive manufacturing (AM) is a promising technology for processing these materials defect-free. In this work we present recent results focusing on both process-structure and structure-property relationships for pure molybdenum and tungsten. Discussion will include implications for high temperature applications and future directions in particular alloy selection.

082 - Using Virtual Reality Technology to Explore Metal Additive Manufacturing  Education
Tejesh Dube, Indiana University - Purdue University Indianapolis

To increase awareness and demonstrate the functionality of metal 3D printing process, we developed a virtual reality (VR) module to simulate the laser powder bed fusion (L-PBF) process. VR has been increasingly used in industry and academia to enhance the overall impact and can provide a much more intuitive link between the computer and the human participants including rapid prototyping, manufacturing, scientific visualization, engineering, and education. The advantage of using the medium of VR for this application is that it really immerses users into a real-world experience. That experience can vitally onboard users with a real metal 3D printing process, after experimenting within a safe environment.

158 - In-Situ Dynamic Thermal Control of Hybrid Manufacturing Processes
Kyle Saleeby, Oak Ridge National Laboratory

Hybrid Manufacturing is the combination of additive (deposition) and subtractive (machining) capabilities within the same manufacturing build volume. This combination of manufacturing technologies enables rapid production of complex geometry with functional, finished surfaces. However, the process of iteratively interleaving additive and machining processes results in severe thermal cycling, influencing material properties of the final component. This research investigates the use of in-situ process monitoring to dynamically control the thermal profile of components produced with Hybrid manufacturing. In-situ thermal image analysis and real-time process information is cohesively managed in a digital architecture, enabling process feedback control of a commercial hybrid manufacturing system. Desired thermal profiles are selected as a setpoint and monitored during production of selected geometries. Two components are produced with dynamic thermal management against an open-loop control. The resulting material properties are compared to evaluate improvement when dynamic thermal control is enabled.

159 - A New Software Tool for Layer-Wise Quality Control in Powder Bed Technologies
Vincent Paquit, Oak Ridge National Laboratory

Additive manufacturing (AM) technologies use a sequence of spatiotemporal events to produce complex geometries, one layer at a time. This process can be observed in real time in its entirety using in-situ monitoring technologies to create a digital twin of the component, digital twin that can then be analyzed to gain a greater understanding of the process-structure-property relationships resulting in unpredictable and nonuniform part quality. This data driven methodology has shown very promising results in commercial applications, paving the way for a new certification and qualification approach for AM components. However, the approach requires specialized tools to analyze the data and to provide reliable quality assurance at every step of the manufacturing process. In this presentation, the authors will discuss a software tool developed at the ORNL Manufacturing Demonstration Facility (MDF) called Peregrine that provides artificial intelligence-based image analysis of in-situ data collected on powder bed technologies for real time quality control. The tool uses machine and camera agnostic algorithms for autonomous detection, classification, and localization of layer-wise powder bed anomalies. Using a novel Convolutional Neural Network architecture, the algorithm is able to return pixel-wise anomaly predictions at the native resolution of the imaging system. Accumulating the layer-wise results over the entire height of each component, the tool builds a 3D defect map that can be visualized to appreciate the quality of the component and to establish a correlation between manufacturing intents and outcome.

004 - Titanium Atomization Technology; Developments Spanning Over 60 years
James Sears, Amaero Additive Manufacturing

Over the course of the last 60 years there have been many developments in the techniques used to atomize Titanium alloys. The reasons for using powder Titanium (PM-TI) for part fabrication has been well established, i.e., the associated reduction in fabrication costs (e.g., reduction in Buy-to-Fly ratio). A major impediment to a wider acceptance for the use of PM Ti has been the high cost of powder production, especially due the shift to finer particle sizes. The original need for fine powder was the result of demand from the MIM industry due to developments of Titanium applications. Now, with the recent focus on Additive Manufacturing, especially Laser Powder Bed Fusion (LPBF), the market for fine Titanium alloy powder has steadily increased. The historical developments in Titanium atomization will be discussed and how it relates to in increased demand from the MIM and AM industries.

114-R - Microstructure and Mechanical Properties of FSLA Steel Produced By The Binder Jet Process
Thomas Murphy, FAPMI, Hoeganaes Corporation

An alloy, called FSLA (free-sintering low-alloy), was designed and implemented for use with binder jet printing.  This work focuses on various heat treatments that can be utilized with the alloy to produce a range of properties for various applications. . The microstructure of the alloy can be varied post-sintering, by heat treatment, to give a wide range of mechanical properties that are suitable for automotive components. The alloy constituents are formulated, so that upon cooling from the sintering temperature, the transformation products allow the alloy to reach the required mechanical properties. The hardenability of the alloy is such that ultimate tensile strengths in excess of 1000 MPa can be obtained by inter-critically annealing the material and air cooling.  Various heat treatments and their corresponding mechanical properties will be reviewed.

228 - A Modified 7068 Aluminum Alloy Designed for Laser Powder Bed Fusion
Brandon Fields, University of California, Irvine

Many additively manufactured alloys exhibit higher strengths when compared to compositionally identical alloys processed via conventional processing routes. However, this enhancement is not observed in 7xxx series Aluminum alloys. These alloys exhibit two complications when printed via Laser-Powder-Bed-Fusion: significant evaporation of strengthening elements from the melt pool and crack formation due to hot tearing during solidification. To address these issues, we have designed and developed a modified Al-7068 alloy with increased alloying accounting for evaporation; in addition, TiC nanoparticles dispersed within the powder eliminate dendritic solidification and restrict grain growth, thus avoiding hot tearing. Printing parameters are optimized for minimum porosity. Trends in alloying elements’ evaporation with laser energy density are quantified using inductively-coupled-plasma mass-spectrometry. The microstructure and mechanical behavior in as-printed and T6-heat-treated conditions are characterized using x-ray diffraction and scanning electron microscopy. The experimental work was complemented by CALPHAD phase stability calculations.

517 - Sustainable Production of Inert Gas Atomised Metal Powders
Paul Davies, Sandvik Additive Manufacturing

The sustainability of inert gas atomised metal powder production is a key factor in supporting the important message that Powder Metallurgy is a green technology. Especially, when applied to the advanced manufacturing technologies of Metal Injection Moulding (MIM) & additive manufacturing, compared with alternative manufacturing technologies. The principal process steps of inert gas atomised metal powder production are analysed, in terms of energy consumption and carbon footprint, while factoring efficiencies, to provide a sustainable low-impact production process. A powder production process that utilizes renewable energy sources and incorporates recycled raw materials, low levels of waste generation and efficient supply chains & logistics. The life cycle of metal powders are reviewed, from raw materials, to gas atomised powder production, consolidated components in service and at end of life.

Pedro Cotait, Rio Tinto Metal Powders

518 - Environment Benefits of Sustainable Hardfacing Coatings
Zhang Zhe, Oerlikon Metco (US) Inc.

Historical focus on the economic impact of wear, has considered the cost of the part or tool replacement versus protecting its surfaces.  If the tool is cheap to manufacture and can be replaced easily without too much effort, then a coating or hardfacing wasn’t a consideration.  Increasingly environmental impact is front-and-center of business strategies and decision making. 
This paper details the environmental benefits in wear reduction, through the use of green and sustainably processed hard phases within a readily applied hardfacing.  Calculations are based on the environmental cost of replacing the raw material in bar-form, compared with carbon dioxide usage of conventional hardfacing material.  Data is used that calculates carbon dioxide use when using conventionally; mined, processed and converted Tungsten Carbides to those sustainably processed.  By reducing wear, the manufacturing carbon foot-print of the sustainable Hardfacing was determined to be about 30 times lower than that of steel.
These carbon benefits are then considered as a function of the mass of hardfacing used and comparisons to equivalent greenhouse and carbon dioxide emissions created by mainstream use.  It further compares the carbon sequestered as a function of acers of forest per annum.