Additive Manufacturing of Refractory Metallic Materials: Additive Manufacturing of Ta-based, Mo-based, and W-based Alloys
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Additive Manufacturing Committee
Program Organizers: Antonio Ramirez, Ohio State University; Jeffrey Sowards, NASA Marshall Space Flight Center; Omar Mireles, NASA; Eric Lass, University of Tennessee-Knoxville; Faramarz Zarandi, RTX Corporation; Matthew Osborne, Global Advanced Metals; Joao Oliveira, Faculdade Ciencias Tecnologias
Wednesday 2:00 PM
March 22, 2023
Room: 24A
Location: SDCC
Session Chair: Jeffrey Sowards , NASA MFSC; Matt Osbourne , Global Advanced Metals
2:00 PM Invited
Influence of Dislocation Structures on Mechanical Response in Additively-manufactured Ta-2.5%W Across Length Scales: Kaila Bertsch1; Marissa Linne1; Stephen Burke1; Riley Wraith1; Joseph McKeown1; Hye-Sook Park1; 1Lawrence Livermore National Laboratory
Tantalum-tungsten alloys are of increasing research interest for applications such as hypersonics, plasma-facing reactor components, and rocket nozzles due to their high melting temperatures and balance of ductility and strength. Additive manufacturing (AM) offers the geometrical flexibility for potential rapid prototyping of these alloys. However, AM can induce distinctive microstructures that influence material performance, ranging from microcracks and pores to dislocation structures, whose effects remain poorly understood. In this work, the mechanical performance of AM and wrought Ta-2.5%W materials were evaluated under uniaxial tension via in situ SEM straining, demonstrating higher yield strength in AM material but similar failure characteristics. The microstructures were further characterized ex situ via SEM, EBSD, EDS, and TEM before and after loading to analyze the microstructural evolution throughout deformation and failure. By linking observations across length scales, new insights were gained regarding the influence of AM defects, segregation, and particularly dislocation structures on mechanical response.
2:30 PM
Characterizing the High Temperature Mechanical Performance and Microstructure of Additively Manufactured Tantalum and Tungsten Alloys: Sharon Park1; Mo-Rigen He1; Gianna Valentino2; Kevin Hemker1; 1Johns Hopkins University; 2JHU Applied Physics Laboratory
Advances in additive manufacturing (AM) hold considerable promise in the fabrication and implementation of refractory-based components via near-net-shape processing, but manufacturing refractories with laser-based techniques is not without its challenges. Moreover, the characterization of refractory high-temperature properties is rare, much less for those made via AM. Here, we investigate the process-microstructure-properties relationships for laser powder bed fusion of tungsten and tantalum alloys characterized at elevated temperatures (~1000C). Initial high-temperature tension testing of tantalum showed the typical behavior of decreasing strength and elongation with increasing temperature. However, an anomalous strain hardening behavior was observed at 400C, resulting in a ~9% increase in the tensile strength compared to ambient temperature. Detailed electron microscopy is ongoing to understand the non-uniform and highly anisotropic AM microstructure impact on the mechanical properties. A similar study will be extended to tungsten alloys to present a mechanistic understanding of AM refractory performance at high temperatures.
2:50 PM
Elucidating the Porosity-Cracking Tradeoff in Laser-based
Additive Manufacturing of Refractory Metals: Gianna Valentino1; Robert Mueller1; Alex Lark1; Li Ma1; Ian McCue2; 1Johns Hopkins Applied Physics Laboratory; 2Northwestern University
Advances in additive manufacturing (AM) promise to be a game-changer in the fabrication and implementation of refractory-based components via near-net-shape processing. However, the high melting temperatures of refractories necessitate the redevelopment of AM processing parameters compared to traditional AM metals (e.g., superalloys, steels). In this study, we develop AM laser parameters for tungsten and tantalum alloys and characterize their mechanical behavior to understand the processing-structure-property relationships. Computational fluid dynamics simulations are used to inform a subset of AM laser parameters that are manufactured and characterized for porosity and underlying microstructure. While low porosity is typically a key metric for success in most AM processing, the results presented here will discuss the need to balance maximizing bulk material density while also minimizing cracking from steep thermal gradients. Although still in its infancy, a study to fabricate refractory graded materials is ongoing and the results will be discussed for thermal management.
3:10 PM Cancelled
Study of Printability and Melt Pool Geometry in W & W -alloys by Laser Powder Bed Fusion: 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 laser powder bed fusion additive manufacturing. Cubes were deposited on a refractory metal baseplate and in an inert atmosphere. The microstructure and cracking of the tungsten & tungsten alloy cubes was also assessed and the cause for porosity in the samples using LPBF process was studied. Furthermore, powderless single beads from different refractory materials were used to understand the melt pool geometry and laser absorptivity. Results showed how alloying and process parameter selection can lead to reduction in defects during laser powder bed fusion of tungsten and its alloys as well as the effects of thermal properties on the melt pool geometries of refractory metals.
3:30 PM Break
3:50 PM Invited
Enabling Future Concepts in Nuclear Energy through the Use of Additive Manufacturing on Titanium – Zirconium – Molybdenum Alloy: John Carpenter1; Michael Brand1; Rose Bloom1; Robin Montoya Pacheco1; 1Los Alamos National Laboratory
Microreactors are currently of interest to the nuclear energy field as a means to provide ‘portable’ power. In order to make these reactors inherently safe, a coreblock is used to provide structural stability. Current coreblock solutions (ex. steels) limit operating temperatures to 600-700°C. The use of titanium – zirconium – molybdenum (TZM) alloys could allow for a substantial increase (2-3X) in operating temperature and, thereby, increasing energy output. Notably, TZM is difficult to form, machine and join. Hence, we are looking at additive manufacturing (AM) as a method to create near-net-shape components with complex geometries. Literature on AM of TZM is available indicating that densities of 99.7% have been achieved. In this work we aim to improve upon this density through a concerted process parameter development effort coupled with mechanical testing in order to identify process-structure-property relationships optimized for nuclear energy applications.
4:20 PM
Development of Molybdenum Alloys for Use with Powder Blown Laser Directed Energy Deposition Additive Manufacturing: Nathaniel Lies1; 1Georgia Institute of Technology
Molybdenum and its alloys are receiving increasing attention for their high strength and impressive thermal properties. With their main detractor being oxidation and difficulty producing parts, Mo is an excellent candidate for atmosphere-controlled 3D printing. This work explores advancements in using laser directed energy deposition (LDED) additive manufacturing to print pure Mo along with first steps towards Mo alloys specifically developed for 3D processes. Vacuum arc melting (VAM) is used to produce new compositions which are mechanically tested and evaluated for use in 3D systems. Emphasis is placed on the search for inoculants and alloying additions that increase ductility while retaining strength at high temperatures.