Additive Manufacturing: Alternative Processes (Beyond the Beam): Binder Jetting
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Additive Manufacturing Committee, TMS: Powder Materials Committee
Program Organizers: Paul Prichard, Kennametal Inc.; Matthew Dunstan, US Army Research Laboratory; Peeyush Nandwana, Oak Ridge National Laboratory; Nihan Tuncer, Desktop Metal; James Paramore, Texas A&M University

Monday 8:00 AM
February 24, 2020
Room: 7A
Location: San Diego Convention Ctr

Session Chair: Paul Prichard, Kennametal


8:00 AM  
Material Property Comparison of Parts Produced Using Binder Jet 3D Printing with Water and Gas Atomized Powders: Andrew Klein1; Kyle Myers1; 1ExOne
    As binder jet 3D printing continues to transition from a prototyping process to a production process for metals, cost and material properties become even more critical. By using gas atomized, spherical powders that are typically used in metal injection molding, binder jet 3D printers have been shown to produce parts that exceed MPIF Standard 35. By introducing water atomized powders or using wider powder distributions, the cost of the raw materials can be greatly reduced. Additionally, process setting flexibility can allow for the process speed and surface finish to be optimized for a given part. This paper will present mechanical properties, print time, and surface finish for gas and water atomized 316L powders.

8:20 AM  
Multifunctional Binder for Binder Jet Additive Manufacturing: Dustin Gilmer1; Lu Han2; Michelle Lehmann1; Amy Elliott2; Tomonori Saito2; 1The University of Tennessee; 2Oak Ridge National Laboratory
    Binder jet additive manufacturing utilizes an inkjet technology to deposit a polymer binder into a powder bed. The layers of powder are glued together, one layer at a time to form a part. The part is removed from the printer and cured in a low-temperature oven. Then, the green part is sintered and infiltrated in a high-temperature furnace. Green part properties including strength, porosity, and resolution significantly impact the final part properties. This study developed several novel polymer binders for binder jetting to improve green parts and final part properties. Particularly, novel polymer binders were developed for sand printing. The binder provides a very high strength of sand parts, stronger than unreinforced concrete. The binder can be washed, which is ideal for sand-casting molds and wash-out tooling, among others. The binder also has other functionalities that enhance the final part properties.

8:40 AM  
Multi-physics Modeling Fframework of Binder Jetting Process: Wenda Tan1; 1University of Utah
    In this work, a multi-physics modeling framework is presented to simulate the important phenomena that determine the process-microstructure relationship for the binder jetting products. In the first stage, a model that integrates a computational fluid dynamics (CFD) and discrete element method (DEM) is used to simulate the fluid dynamics of the binder droplets (high-speed impact, deformation, and imbibition) and the powder motion (due to the droplet impact). The model will predict the powder bed structure after the binder jetting process. In the second stage, a phase field model is used to simulate the particle coalescence and microstructure evolution during the sintering process. The model will predict the porosity and microstructure after the sintering process. This modeling framework will provide a useful approach for the physics understanding and/or process optimization for this process.

9:00 AM  
Evolution of Pore Distribution in the Binder Jetting of WC-Co: Paul Prichard1; 1Kennametal Inc.
    Binder jetting is an additive manufacturing process which uses drop on demand print technology to produce complex 3D objects. The organic binders must subsequently be removed, and the 3D objects sintered to near full density. The as-printed microstructures contain a wide distribution of porosity resulting from the printing process, powder packing arrangement and powder synthesis process. Print parameters such as droplet size, binder saturation percentage and layer thickness are the key parameters, which have an influence on the porosity size and distribution. The sintering process required to create full density components is dependent on the powder arrangement and the pore distribution in the as-printed structure. This presentation will discuss the relationship between the print parameters, pore size distribution and the resulting sintered microstructures.

9:20 AM  
Effects of Printing Parameters on Green and Final Part Density of Binder Jet Printed WC-Co: Katerina Kimes1; Pierangeli Rodriguez De Vecchis1; Danielle Brunetta1; Drew Elhassid2; Markus Chmielus1; 1Univ of Pittsburgh; 2General Carbide Corporation
    Tungsten carbide-cobalt (WC-Co) is a cermet material known for its excellent mechanical properties. Its microstructure is composed of hard, brittle carbide grains surrounded by a tough Co-matrix. Traditionally, WC-Co parts are shaped by pressing, extruding, or molding, resulting in low-density green parts held together by wax, later de-waxed and sintered. This process is restricted both by mass production and shape detail. Additive manufacturing, particularly binder jet-printing is an alternative to produce specific, highly complex shapes in a cost and time effective manner. Fine-particle WC-Co powder was provided by General Carbide Corporation and characterized as nearly-spherical agglomerates composed of nano-sized particles. The design of experiments method was employed to determine optimal parameters for powder bed packing and also for printing. Parts sintered and HIPed at General Carbide were analyzed for hardness and density. With optimal parameters, parts can be binder jet printed with mechanical properties and microstructures comparable to traditionally-manufactured parts.

9:40 AM Break

10:00 AM  
Processing Parameters for H13 Utilizing Binder Jet Additive Manufacturing: Dustin Gilmer1; Tomonori Saito1; Peeyush Nandwana2; Amy Elliott2; 1University of Tennessee Knoxville/Oak Ridge National Laboratory Bredesen Center; 2Oak Ridge National Laboratory
    Binder jet additive manufacturing (AM) is a growing field that presents large upsides in the production of metal parts. By utilizing powder metallurgy and the binder jet AM process, it is possible to create near net shaped parts, and binder jet has been shown to maintain higher productivity and lower operation costs than other metal AM methods. H13 is a tool steel that is utilized to create many hot working tools for manufacturing. Traditionally, binder jetting H13 parts that meet chemical specifications has been challenging due to the addition of carbon by the binder. One way to combat this challenge is to create parts utilizing minimal binder, but the low content of binder often leads to parts that break before they can be sintered. Thus, careful balancing between binder content and carbon pickup must be made. In this study, Oak Ridge National Laboratory researched processing parameters to minimize carbon pickup and to produce viable preforms for handling.

10:20 AM  
3D-printing and Consolidation of 316L Stainless Steel Powder Components: Ifeanyichukwu Olumor1; Geuntak Lee1; Eugene Olevsky1; 1Mechanical Engineering, San Diego State University
    A unique binder jetting method is employed in printing 316L stainless steel components with the aim of improving both the green density of printed parts and subsequently sintered components. In this method, a water-soluble binder is premixed with 316L stainless steel powder before printing. During printing, water is jetted unto the powder/binder mixture to selectively activate the binder, layer by layer. The effects of printing parameters such as layer height, roller speed, shaking speed, powder/binder ratio and amount of jetted water (nozzle temperature) on the green density and sintered components are investigated. Results show that layer height and nozzle temperature affect the density and dimensional accuracy of the green compact. Results show that on reducing layer height, green density increases. However, the dimensional accuracy of the printed samples decreases, especially in the Z-direction.

10:40 AM  
Effect of Print Parameters on Dimensional Accuracy and Sintering Behavior of Binder Jet 3D Printed Water and Gas Atomized Inconel 625: Runbo Jiang1; Lorenzo Monteil1; Katerina Kimes1; Markus Chmielus1; 1University of Pittsburgh
    Binder jet 3D-printing (BJ3DP) is a solid-state powder bed additive manufacturing process. Powder bed additive manufacturing in general has seen remarkable growth in recent years due to its ability to produce metal components with complex geometries and feature with minimal lead time and waste material. The aim of this research is to investigate the relation between process parameters in BJ3DP and the properties of coupons with the same geometry. Binder saturation was determined as the most important factor affecting green density out of five printing parameters, including oscillation speed, recoat speed, roller traverse speed, and roller rotation speed for water atomized Inconel 625 alloy through fractional factorial design of experiment. Detailed examination of the effect of binder saturation was performed on both irregular water atomized and spherical gas atomized powders. The green density, dimensional accuracy, sintered density, shrinkage and mechanical properties was investigated.

11:00 AM  
The Effect of Sintering Condition on the Microstructure Evolution of Binder-jet Printed IN625 Alloy: Amir Mostafaei1; Chuyuan Zheng2; Pierangeli Rodriguez2; Ian Nettleship2; Markus Chmielus2; 1Carnegie Mellon University; 2University of Pittsburgh
    Binder-jet 3D printing (BJ3DP) of IN625 provides a greater degree of freedom in shaping than traditional manufacturing. However, remnant porosity in sintered material is damaging to properties such as fatigue strength. It is assumed that the remnant pore population is determined by the initial defects introduced by BJ3DP and the inability of pressureless sintering to remove them. A quantitative study including the evolution in pore size distribution and pore shape during supersolidus sintering and subsolidus sintering was performed on gas-atomized IN625 samples printed with three different particle size distributions (PSD). The results showed that large pore sections were preferentially eliminated at short times during supersolidus sintering but not subsolidus sintering. This was attributed to viscous particle rearrangement. In addition, micro-CT of the as-printed green bodies was used to visualize the pore network in 3D and demonstrated that the packing defects introduced by printing can be controlled by tuning the PSD.

11:20 AM  
Effect of Print Processing Parameters on the Green Part Properties and Densification Behavior in Binder Jet 3D Printed Co-Cr Biomaterials: Amir Mostafaei1; Anthony Rollett1; 1Carnegie Mellon University
    Casting was a traditional manufacturing method for Co-Cr biomaterials to produce implants and partial dentures and the fabrication of complex geometry with overhang structure and internal microchannels is challenging when using traditional manufacturing methods. Binder jetting is a process of joining powdered materials using a polymeric binder followed by post-processing including curing and densification steps. Here, Co-Cr biomaterial is used to 3D-print parts with various print process parameters such as binder saturation and layer thickness followed by sintering process. Sintering temperature and holding time affect linear shrinkage, densification and pore evolution. A database of microstructure evolution such as grain and pore intercept length, pore separation, surface area per unit volume and number of pore sections per unit area will be developed to better understand sintering kinetics, microstructural evolution and, finally, sintering mechanisms of binder jetted Co-Cr biomaterials.