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Powder Development and Characterization for Additive Manufacturing of FeMnAlC Alloy Steel

Description:

TECHNOLOGY AREA(S): Materials 

OBJECTIVE: This project seeks the development of an additive powder with the same composition as the lightweight armor steel, FeMnAl, for future repair of components made of this steel, and design of new components. 

DESCRIPTION: FeMnAl is a lightweight, high-strength steel alloy with Fe-28Mn-9.5Al-1Si-0.5Mo-0.9Cdeveloped for armor applications. The Army is interested in using this steel to reduce weight in a variety of ground vehicle platforms. While a high-alloy steel, it is a single phase, with age-hardenability. This means there are fewer concerns with rapid solidification, as martensite cannot form, and heat treatment can be used to control the hardness of the final part. Similarly, there is growth in the development of additive manufacturing repair techniques for ground vehicles. However, there is not currently a similar high-alloy steel powder available. Additive repairs requires compatibility with this high alloy steel, which in turn requires unique powder compositions. The unique chemistry of this alloy is expected to be challenging, and require innovative processes to manufacturing in powder form. This steel has been produced via traditional metal manufacturing techniques, in both cast and wrought forms. No attempt has been made to develop a powder form of this material. 

PHASE I: In Phase I, the small business will assess the capability to make high alloy powders near this composition. This powder will be compatible with Directed Energy Deposition, with a powder size of 60 to 125µm. Compositional validation will be required. High rating will be placed on compositional evaluation using wet chemistry methods, due to known limitations of optical emission and spark spectroscopy for this composition. Feasibility of process will be demonstrated by production of a small batch of powder of the intended composition. Deliverables shall include materials data and physical powder samples. 

PHASE II: In Phase II, the small business will improve processing to make powder within compositional tolerances, targeting uniformity throughout the batch. This phase will include characterization of the powder produced by various metrics [Slotwinski], and manufacture of test articles, such as density, hardness, and metallographic samples. The final deliverable will include: • Composition testing results • Material test results • Documentation of powder characteristics (size distribution, particle density, particle morphology, particle crystalline phases) 

PHASE III: In the final Phase of the project, the contractor will determine capability to produce the powder in larger scales, and develop a strategy for qualification. The final powder should easily transition to customers interested in light weighting, particularly in wear-sensitive regions. Powder would be made available to Programs of Record, such as PdM Abrams, for purchase and use for repair of their systems in which FeMnAl has been integrated. It may also be used in future design of specific components with significant weight restrictions. 

REFERENCES: 

1: Zimmerman, B, Allen, E., "Analysis of the Potential Impact of Additive Manufacturing on Army Logistics", Naval Postgraduate School Monterey Ca, (Dec 2013). http://www.dtic.mil/get-tr-doc/pdf?AD=ADA620821

2:  Slotwinski, J.A., et. al. "Characterization of Metal Powders Used For Additive Manufacturing", J. Rsch. NIST (2014). https://nvlpubs.nist.gov/nistpubs/jres/119/jres.119.018.pdf

3:  Howell, R.A. "Microstructural influence on dynamic properties of age hardenable FeMnAl alloys", Missouri University of Science and Technology (2009). http://scholarsmine.mst.edu/doctoral_dissertations/1940/

4:  "DoD Additive Roadmap" https://www.americamakes.us/our_work/technology-roadmap/

5:  University of Loughborough, "About Directed Energy Manufacturing" http://www.lboro.ac.uk/research/amrg/about/the7categoriesofadditivemanufacturing/directedenergydeposition/

KEYWORDS: Steel, Additive Manufacturing, Powder Metallurgy, Metallic Alloys 

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