Supersolidus liquid phase sintering of water-atomized low-alloy steel in binder jetting additive manufacturing.

This work investigates the feasibility of net shape manufacturing of parts using water-atomized (WA) low-alloy steel with comparable densities to conventional powder metallurgy parts via binder jetting additive manufacturing (BJAM) and supersolidus liquid phase sintering (SLPS). In this study, a modified water-atomized powder grade with similar composition as MPIF FL-4405 was printed and pressure-less sintered under a 95% N2-5% H2 atmosphere. Combinations of two different sintering schedules (direct-sintering and step-sintering) and three different heating rates (1, 3, and 5 °C/min) were applied to study the densification, shrinkage, and microstructural evolution of BJAM parts. This study demonstrated that, although the green density of the BJAM samples was ∼42% of the theoretical density, the sintered parts experienced large linear shrinkage up to ∼25% and reached ∼97% density without compromising shape fidelity. This was ascribed to a more homogeneous pore distribution throughout the part before ramping up to the SLPS region. The synergistic effects of carbon residue, the slow heating rate, and the additional isothermal holding stage at the solid-phase sintering region were determined to be the key factors for sintering BJAM WA low-alloy steel powders with resulting minimal entrapped porosity and good shape fidelity.

Powder Reuse Cycles in Electron Beam Powder Bed Fusion-Variation of Powder Characteristics.

A path to lowering the economic barrier associated with the high cost of metal additively manufactured components is to reduce the waste via powder reuse (powder cycled back into the process) and recycling (powder chemically, physically, or thermally processed to recover the original properties) strategies. In electron beam powder bed fusion, there is a possibility of reusing 95-98% of the powder that is not melted. However, there is a lack of systematic studies focusing on quantifying the variation of powder properties induced by number of reuse cycles. This work compares the influence of multiple reuse cycles, as well as powder blends created from reused powder, on various powder characteristics such as the morphology, size distribution, flow properties, packing properties, and chemical composition (oxygen and nitrogen content). It was found that there is an increase in measured response in powder size distribution, tapped density, Hausner ratio, Carr index, basic flow energy, specific energy, dynamic angle of repose, oxygen, and nitrogen content, while the bulk density remained largely unchanged.

Data related to the effect of specimen geometry and orientation on tensile properties of Ti-6Al-4V manufactured by electron beam powder bed fusion.

Additive manufacturing quality assessment often relies on tensile testing as the preferred methodology to qualify builds and materials. The data included in this article provides additional supporting information on our manuscript (Shanbhag et al., 2021) on the effect of specimen geometry and orientation on tensile properties of Ti-6Al-4V manufactured by electron beam powder bed fusion. As such, the data in brief provides in-depth details on the tensile specimen specifications, the tensile specimen build layout and replicate notations, and the tensile testing datasets. The information presented herein complements the manuscript.

Data related to architectural bone parameters and the relationship to Ti lattice design for powder bed fusion additive manufacturing.

The data included in this article provides additional supporting information on our publication (McGregor et al. [1]) on the review of the natural lattice architecture in human bone and its implication towards titanium (Ti) lattice design for laser powder bed fusion and electron beam powder bed fusion. For this work, X-ray computed tomography was deployed to understand and visualize a Ti-6Al-4V lattice structure manufactured by laser powder bed fusion. This manuscript includes details about the manufacturing of the lattice structure using laser powder bed fusion and computed tomography methods used for analyzing the lattice structure. Additionally, a comprehensive literature review was conducted to understand how lattice parameters are controlled in additively manufactured Ti and Ti-alloy parts aimed at replacing or augmenting human bone. From this literature review, lattice design information was collected and is summarized in tabular form in this manuscript.

Data related to the experimental design for powder bed binder jetting additive manufacturing of silicone.

The data included in this article provides additional supporting information on our recent publication (Liravi et al., 2018 [1]) on a novel hybrid additive manufacturing (AM) method for fabrication of three-dimensional (3D) structures from silicone powder. A design of experiments (DoE) study has been carried out to optimize the geometrical fidelity of AM-made parts. This manuscript includes the details of a multi-level factorial DOE and the response optimization results. The variation in the temperature of powder-bed when exposed to heat is plotted as well. Furthermore, the effect of blending ratio of two parts of silicone binder on its curing speed was investigated by conducting DSC tests on a silicone binder with 100:2 precursor to curing agent ratio. The hardness of parts fabricated with non-optimum printing conditions are included and compared.

Data related to the sinter structure analysis of titanium structures fabricated via binder jetting additive manufacturing.

The adoption of metal binder jetting additive manufacturing (AM) for functional parts relies on a deep understanding between the materials, the design aspects, the additive manufacturing process and sintering. This work focuses on the relationship between sintering theory and process outcomes. The data included in this article provides additional supporting information on the authors' recent publication (Wheat et al., 2018 [1]) on the sinter structure analysis of commercially pure titanium parts manufactured using powder bed binder jetting additive manufacturing. For this work, commercially pure titanium was deployed to study the effect of powder size distributions on green and sintered part qualities (bulk density, relative density, particle size, pore size, sinter neck size). This manuscript includes the overall computed tomography visualization methods and results for the green and sintered samples using uni- and bi-modal powders. Moreover, the effective particle and pore size for the different batches of powder are presented.

Effect of glycerol concentrations on the mechanical properties of additive manufactured porous calcium polyphosphate structures for bone substitute applications.

This article addresses the effects of glycerol (GLY) concentrations on the mechanical properties of calcium polyphosphate (CPP) bone substitute structures manufactured using binder jetting additive manufacturing. To achieve this goal, nine types of water-based binder solutions were prepared with 10, 12.5, and 15 wt % GLY liquid-binding agent, mixed, respectively, with 0, 0.75, and 1.5 wt % ethylene glycol diacetate (EGD) flow enhancer. The print quality of each of the solutions was established quantitatively using an image processing algorithm. The print quality analysis narrowed down the solutions to three batches containing 1.5 wt % EGD and variable amount of GLY. These solutions were used to manufacture porous CPP bone substitute samples, which were characterized physically to determine shrinkage, porosity, microstructure, and compression strength. The 12.5 wt % GLY, 1.5 wt % EGD solution resulted in the highest mechanical strength after sintering (34.6 ± 5.8 MPa), illustrating similar mechanical properties when compared to previous studies (33.9 ± 6.3 MPa) of additively manufactured CPP bone substitutes using a commercially available binder. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 828-835, 2017.

Optical design and Initial Results from The National Institute of Standards and Technology's AMMT/TEMPS Facility.

The National Institute of Standards and Technology's (NIST) Physical Measurement and Engineering Laboratories are jointly developing the Additive Manufacturing Measurement Testbed (AMMT)/ Temperature and Emittance of Melts, Powders and Solids (TEMPS) facilities. These facilities will be co-located on an open architecture laser-based powder bed fusion system allowing users full access to the system's operation parameters. This will provide users with access to machine-independent monitoring and control of the powder bed fusion process. In this paper there will be emphasis on the AMMT, which incorporates in-line visible light collection optics for monitoring and feedback control of the powder bed fusion process. We shall present an overview of the AMMT/TEMPS program and its goals. The optical and mechanical design of the open architecture powder-bed fusion system and the AMMT will also be described. In addition, preliminary measurement results from the system along with the current status of the system will be described.