Additive Manufacturing of Metals: Microstructure, Properties and Alloy Development: High Temperature and Refractory Materials
Program Organizers: Prashanth Konda Gokuldoss, Tallinn University of Technology; Jurgen Eckert, Erich Schmid Institute of Materials Science; Zhi Wang, South China University of Technology

Wednesday 8:00 AM
October 12, 2022
Room: 301
Location: David L. Lawrence Convention Center

Session Chair: Farahnaz Haftlang, Pohang University of Science and Technology; Veeraraghavan Sundar, Ues Inc.


8:00 AM  
Temporary Coating to Improve Part Integrity and Post-Sintering Surface Roughness of Binder Jet Printed Tungsten Carbide-Cobalt Parts: Pierangeli Rodriguez De Vecchis1; Katerina Kimes2; Drew Elhassid3; Markus Chmielus1; 1University of Pittsburgh; 2Desktop Metal; 3General Carbide
    Traditionally, tungsten carbide-cobalt (WC-Co) parts are manufactured by powder injection molding (PIM), but Binder Jet Printing (BJP) allows to create custom-shapes and complex geometries. Even though BJP of WC-Co has been achieved, the process is not ideal. The intrinsic complexity of WC-Co powders results in low-density (~20%) green parts, which tend to crack during handling before sintering and result in deformed parts after densification. This project proposes to evaluate three coatings (ExOne solvent binder 04, Cerita 983 runner wax from Paramelt Inc. and PIM Paraffin wax) that would protect the green part and ensure better integrity after sintering. Average surface roughness (Ra) performed via optical profilometry was chosen to evaluate distortion of the printed part. Results showed a significant reduction of Ra and its variation in all orientations for binder-coated samples in comparison with non-coated samples. Additionally, Archimedes density, volumetric shrinkage, microstructural characterization, and Rockwell A hardness were also compared.

8:20 AM  
Fabrication of Molybdenum Based Refractory Alloys Using Additive Manufacturing: Christopher Ledford1; Patxi Fernandez-Zelaia1; Michael Kirka1; 1Oak Ridge National Laboratory
    Molybdenum based refractory materials are well suited to benefit from the layer-by-layer processing advantages that come from additive manufacturing. Nonetheless, obtaining high density and defect free material is a nontrivial task which requires high processing temperatures along with clean inert environments. Here we present our work on the processing of various molybdenum based refractory alloys using additive manufacturing to produce fully dense, crack-free material. In addition, we investigate the resulting process-sensitive microstructures and corresponding property relationships.

8:40 AM  Cancelled
Laser Powder Bed Fusion of Platinum-based Alloys for Industrial High Temperature Structural Applications: Biao Cai1; Selassie Dorvlo2; Ian Campbell2; Moataz Attallah1; Parastoo Jamshidi1; 1University of Birmingham; 2Cookson Gold
    Additive manufacturing (AM) of platinum alloys is of great interest for the production of structural components for high temperature industrial and space applications in aggressive atmospheres due to their creep resistance and outstanding chemical stability, oxidation and corrosion resistance1. In this study for the first time the potential for AM of Pt-Rh10wt% alloy for industrial applications was investigated. Laser Powder Bed Fusion (LPBF) was used to manufacture the test specimens, characterising the density, hardness, ultimate tensile testing and oxidation rate at high temperature. The study illustrated the successful manufacture of Pt-Rh10 parts with porosity level as low as ~ 0.1% after AM process optimisation. It was found that the LPBFed parts outperform that of the cast Pt-Rh10 in terms of the mechanical performance. Assessment of the oxidation rate at high temperature of 1550°C demonstrated low level of weight change confirming their acceptable oxidation rate for final use at high temperatures.

9:00 AM  
Printability and Defects in W & W -alloys by Directed Energy Deposition: Amaranth Karra1; Maarten de Boer1; Bryan Webler1; 1Carnegie Mellon University
    This study examines microstructure and mechanical properties of pure tungsten and tungsten alloys additively manufactured by powder-feed directed energy deposition additive manufacturing. Cubes were deposited on a refractory metal baseplate. The layer height was experimentally decided as a function of powder, travel speed, and powder feed rate by the quantification of already printed cubes. The microstructure and cracking of the tungsten & tungsten alloy cubes was also assessed and the cause for porosity in the samples using DED process was studied. Results showed how alloying and process parameter selection can lead to reduction in defects during direct energy deposition of tungsten and its alloys.

9:20 AM  
A Direct Laser Deposition Investigation of Microstructure-Processing-Property Relationships in NbVZr-based Alloys: Katharine Padilla1; Mu Li1; Zhaohan Zhang1; Rohan Mishra1; Katharine Flores1; 1Washington University in St. Louis
    Many studies of refractory complex concentrated alloys (RCCA) focus on identifying equiatomic, single-phase solid solution alloys with high ductility and other favorable mechanical properties. However, multiphase alloys offer an additional degree of design flexibility and the potential for superior performance. In this work, we apply direct laser deposition as a rapid method to investigate the microstructure-laser processing-mechanical property relationship in NbVZr-based alloys. In NbVZr microstructural libraries synthesized under a wide range of heating and cooling rates, we observe BCC dendrites separated by two Laves phases, cubic C15 and hexagonal C14, which grow finer with decreasing heat input. Dendrite size, spacing, and morphology are correlated with laser power and travel speed. Nanoindentation experiments are performed to investigate the relationship between microstructure and mechanical properties. The same technique will be used for NbVZrMx compositional libraries, where we explore the added effects of composition variations to structure-processing-property relationships.

9:40 AM  
Laser Powder Bed Fusion of Pure Nb Powder and Nb+WC Powder Blend: Ana Sofia d'Oliveira1; Eloisa Cardozo1; Moataz Attallah2; 1Universidade Federal do Paraná; 2University of Birmingham
    A study was performed to investigate the impact of Laser Powder Bed Fusion (LPBF) parameters on the densification of pure Nb powder and Nb+2.5 Wt.%WC powder blend. Both materials have good processability, as confirmed by the lack of structural defects when the parameters are optimised. The presence of WC particles led to a reduction in the cracking density. Increasing both scan velocity and laser power resulted in a hardness increase in pure Niobium builds due to oxygen pickup. However, processing the Nb+2.5wt% WC blend led to a different response due to the process parameters. The hardness showed a reduction of 20% on builds processed with Nb+2.5wt%WC, compared with the pure Nb. The hardness development was associated with the effect of the dissociation of the carbide, as well as the lack of solid solution hardening effect expected due to the full solubility of W in Nb and the formation of carbides.

10:00 AM Break

10:20 AM  
Microstructure and Mechanical Properties of Co-based Superalloy with γ/γ' Microstructure Fabricated by Laser Powder-bed Fusion: Hyeji Im1; Chuan Liu1; Carelyn Campbell2; David Dunand1; 1Northwestern University; 2NIST
    Cobalt-based superalloys with high tungsten content can operate at higher temperatures as compared to Ni-based superalloys, thus improving efficiency of gas turbines and jet engines. Additively-manufactured Co-based superalloys can help overcome the challenges of poor machinability and difficulties casting complex, thin-walled geometries. However, cracking during additive fabrication is a significant barrier for further development. A set of prototype Co-base superalloys (Co-Ni-Al-W) were chosen using CALPHAD-based thermodynamic predictions to minimize the freezing range and maximize the γ' fraction for the given alloy system. The prototype alloys were fabricated via laser powder-bed fusion and heat-treated. Microstructural characterization after laser melting and heat treatments demonstrated a crack-free, fully-dense alloy. We present evolution of γ' precipitation on aging and mechanical properties. This research was funded through the U.S. Department of Commerce, National Institute of Standards and Technology (NIST) via award 70NANB14H012 as part of the Center for Hierarchical Material Design (CHiMaD).

10:40 AM  Cancelled
Sintering Process Optimization for FeCrAl and FeCrAl/Binder Composites for Use in Material Extrusion Additive Manufacturing: Amrita Lall1; Zachary Kennedy1; Josef Christ1; Saumyadeep Jana1; 1Pacific Northwest National Laboratory
    Iron-chromium-aluminum (FeCrAl) alloys are ferritic stainless-steels are used in several high-temperature applications because of their superior mechanical properties, corrosion, and oxidation resistance, due to the formation of a protective alumina film. Fabrication of FeCrAl alloy parts by metal extrusion additive manufacturing (MEAM) is a novel concept, allowing efficient manufacturing of complex designs, and thus warrants a comprehensive study of the densification/sintering process. In the current research, sintering studies were performed on gas-atomized FeCrAl powder, consisting of 19-23.5% Cr, 4.5-5.5% Al, by wt.%, and FeCrAl/polymeric-binder composites by varying time, temperature, and environment. Vertical dilatometer was used to find the sintering temperature range and consequently, furnace sintering trials were conducted at temperatures up to 1400C, for up to 24 hours in various environments. Effect of varying sintering parameters and binder chemistry on sintering kinetics, densification, and microstructure was analyzed using Optical and SEM imaging, EDS/ EBSD scans, XRD, TEM and density measurements.

11:00 AM  
Suitability of CoCrFeMn(Ni3Al)x High Entropy Alloys for Additive Manufacturing: Zachary Sims1; Aurelien Perron1; Alfred Amon1; Hunter Henderson1; Michael Thompson2; Max Neveau2; Orlando Rios2; Scott McCall1; 1Lawrence Livermore National Laboratory; 2University of Tennessee Knoxville
     High entropy alloys design continues to be a focus of metallurgical research targeted at next generation applications. The complex manufacturing processes needed to produce these materials remain a barrier to adoption. Additive manufacturing is emerging as a strong candidate for achieving net shape geometry. Expanding the number of families assessed for suitability to additive manufacturing is a key step towards realizing the potential of high entropy materials in application to achieve increased strength, higher corrosion resistance, and better elevated temperature performance compared to contemporary materials. The CoCrFeMn(Ni3Al)x alloy family is tunable to single phase or dual phase with varying (Ni3Al)x additions and heat-treatment. The results of CALPHAD modeling, laser traces, hardness measurements, phase compositions, and microstructural analysis will demonstrate that the CoCrFeMn(Ni3Al)x family is compatible with additive manufacturing.This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.