Additive Manufacturing: Beyond the Beam III: Binder Jetting
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Powder Materials Committee, TMS: Additive Manufacturing Committee
Program Organizers: Brady Butler, US Army Research Laboratory; Peeyush Nandwana, Oak Ridge National Laboratory; James Paramore, US Army Research Laboratory; Nihan Tuncer, Desktop Metal; Markus Chmielus, University of Pittsburgh; Paul Prichard, Kennametal Inc.

Monday 8:30 AM
February 28, 2022
Room: 263C
Location: Anaheim Convention Center

Session Chair: Peeyush Nandwana, Oak Ridge National Laboratory

8:30 AM  
3D Binder-jet Printed Metal Filters: Aaron Acierno1; Teddi Sedlar1; Eric Rhodes1; Markus Chmielus1; 1University of Pittsburgh
    Reusable and self-sterilizing 3D-printed porous metal structures seek the potential to become a reliable and sustainable source of filtration, not only in emergency situations such as during the COVID-19 pandemic through usage of N95 mask filters, but also as air filters in HVAC systems. In order to quantify important microstructural characteristics of these filters, the 3D pore networks were characterized using micro X-ray computed tomography (MicroCT), and pressure drop and particle filtration was tested and compared to different metal powders and post-processing heat treatment conditions. Additionally, 2D cross-section image sequences were considered to predict filtration characteristics and pressure drop. It is seen that anisotropic permeability provides the capability for further filtration tailoring as elucidated through porosity characterization. In this talk, we discuss how processing parameters affect the 3D microstructure and filtration characteristics for subsequent sets of starting powders.

8:50 AM  
Binder Jet Additive Manufactured H13: Microstructure Evolution and Properties: Peeyush Nandwana1; Rangasayee Kannan1; Kinga Unocic1; 1Oak Ridge National Laboratory
    Binder jet additive manufacturing (BJAM) has the potential for industry adoption for tooling and heavy-duty engine applications owing to low capital costs and scalability. The near net shaping enabled by BJAM can enable the use of difficult to machine materials for heavy duty pistons. We have used supersolidus liquid phase sintering (SLPS) to densify H13 steel fabricated via BJAM followed by hot isostatic pressing (HIP) to reduce the porosity in the sintered parts. Microstructural evolution during SLPS and the underlying mechanisms will be presented. We show that abnormal grain growth can occur during sintering whereas the solidification of liquid formed during SLPS can result in solute segregation. Further, the impact of post processing steps such as HIP and heat treatment on the resulting microstructure and tensile properties will be discussed.

9:10 AM  
Impact of Grain Boundary Mobility on Decreasing Porosity in Metal Binder Jetting of Free-sintering Low-alloy Steel: Stephen House1; Pedro De Souza-Ciacco1; Javier Carreno1; Jackeline Vicente-Vazquez1; Calixto Garcia1; 1University of Pittsburgh
    Metal Binder Jetting (MBJ) Additive Manufacturing (AM) involves the deposition of metal powder layer-by-layer, held together by a polymeric glue/binder. The printed part is then sintered to its final shape and density. Minimizing residual porosity remains a key issue for MBJ – particularly for applications with high-cycle-time fatigue (e.g., automotive) – compared to Laser Powder Bed Fusion, a more-established AM technique. The dual-phased Free-Sintering Low-Alloy (FSLA) steel is designed for enhanced diffusion at the sintering temperature to promote high densities, and its microstructure can be tailored by post-sintering heat treatment to produce a wide range of mechanical properties. Herein we present our investigation of the microstructural characteristics of the FSLA system and the impact of grain boundary mobility on decreasing the porosity of MBJ-printed components. By employing nano- to micro-scale characterization (S/TEM, SEM, EBSD, micro-indentation) and modeling, we show how 98% of the theoretical density of ferrite can be achieved.

9:30 AM  
Droplet-powder Interactions in Binder Jetting: From Droplet to Line to Layer to Part: Nathan Crane1; Trenton Colton1; Colton Inkley1; 1Brigham Young University
    Binder jetting (BJ) defines part geometry by inkjet printing binder into a thin layer of loose powder. The interactions of the droplets with the powder influence the final quality of the parts. For example, powder rearrangement, balling, and bleeding can generate defects that remain in the final part. Yet, the complex interactions in the printing process remain relatively poorly understood. This work utilizes an open binder jetting platform to systematically compare the parameters that allow for successful formation of different geometries from lines to 3D parts in a fine 316 SS powder. The impact of printing on geometry formation, surface roughness, and effective saturation are reported. These results show that information from simple primitives fail to predict 3D part behavior. Optimization of printing parameters such as droplet/line spacing can improve surface quality, reduce defects, and optimize printing speeds.

9:50 AM Break

10:10 AM  
Print Parameter Effects on Porosity Distribution in Binder Jetting of WC-Co: Paul Prichard1; Hadi Miyanaji1; Zhuqing Wang1; 1Kennametal Inc.
    Cemented tungsten carbide is an important industrial material, which is typically manufactured into metal cutting tooling and wear components by conventional powder processes. However, complex cemented tungsten carbide components with unique features can be additively manufactured by the binder jetting, which is more suitable than energy beam processes for producing non-weldable materials. The interrelationship between powder flowability and printing parameters determines the size, orientation, and distribution of porosity. These characteristics affect the powder flowable and the energy absorbed during the binder droplet impact. The jetting of binder into a powder bed has been shown to introduce porosity due to powder particle ejection. In addition, an excessive amount of binder may produce binder pooling to create large voids, which may not be easily closed during sintering. This presentation will discuss the interaction between powder characteristics, print parameters and binder fluid characteristics which create porosity during printing and sintered product.