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Metal Powder Based Additive Manufacturing for use in Portable System in an Expeditionary Environment

Description:

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Advanced Infrastructure & Advanced Manufacturing, Sustainment & Logistics OBJECTIVE: Develop a metal powder based additive manufacturing system suitable for deployment in expeditionary environments to manufacture complex metal components with minimal post processing requirements to support contested logistics scenarios. DESCRIPTION: The current state of the art utilizes conventional manufacturing technologies such as computer numerical controlled (CNC) machine tools such as mills, lathes, and plasma cutters, which are augmented by various manually operated metal working machines to fabricate metal components. Depending on the component, this process can involve numerous steps to achieve complex features necessary to meet specifications. Additionally, operators require significant skill levels to operate these machines effectively and efficiently in order to rapidly produce components. This all adds up to cumbersome, inefficient approaches to sustain materiel in the field. Compared to conventional manufacturing technologies, additive manufacturing (AM) is the revolutionary process of creating three-dimensional objects by the successive addition of material which starts with a digital model, usually generated by computer-aided design (CAD)1. AM introduces a new design paradigm that allows the fabrication of geometrically complex parts that cannot be produced by traditional manufacturing and assembly methods2. Furthermore, AM can expedite fabrication of complex components which require extensive skills and many operations to achieve using conventional methods, reducing time to product and therefore the buy-to-fly ratio3. One particular AM process is Metal Powder Bed Fusion (PBF), which, per internal government research, may be ideal to manufacture complex metal components to enable agile sustainment of armaments systems in expeditionary environments. While metal PBF may be the optimal AM process for DoD mission needs, it comes with many risks and challenges. First and foremost, the high surface-to-volume ratio of powder particles coupled with the reactive nature of these metals means that special care must be taken when handling them. Powder explosions are unfortunately still a regular occurrence internationally and these often result in serious injury and loss of life4. Therefore, minimizing handling of powdered metal materials is essential to safe operations. Possible approaches include but are not limited to automation of part excavation and powder reclamation and/or use of material cartridges to eliminate manual powder loading. Another challenge is the requirement for an inert atmosphere for the PBF process. The role of the inert atmosphere during powder bed fusion (PBF) is to remove the process by-products and the air that is initially present in the process chamber5. By today’s standard, Argon is most common with laser processing. Nitrogen is also an option which could minimize logistical burdens by allowing use of a Nitrogen generator but, thus far, this option limits print quality for certain materials5. One possible approach to overcome this challenge might entail process development to utilize vacuum in place of gas to achieve the inert atmosphere, which has had success with electron beam processing. PHASE I: Research, modeling, and simulation of novel approaches to improve PBF machine processes, design, and other considerations including but not limited to safe powder storage, handling, and processing to reduce or eliminate exposure to powder materials during material loading or unloading and part excavation, alternative strategies to inert chambers to decrease dependence on process gases, and increased survivability of equipment during transport over rugged terrain (MIL-STD 810). Collaboration between government, industry, and academia will further develop and refine requirements. Develop a test plan for mechanical properties and metallurgy to establish a baseline upon which improvements can be made through process development in follow-on work. PHASE II: Development and engineering of metal PBF AM equipment resulting in a functional prototype which meets requirements developed during Phase I and is proven through extensive testing. Test results must prove that the developed machine can operate in austere conditions with maximum operator/facility safety and minimal logistics requirements while surviving exposure to the military field environment. Testing of materials to determine baseline mechanical and metallurgical properties should be executed and well documented. PHASE III DUAL USE APPLICATIONS: The development of metal PBF AM machines to meet this mission requirement will augment sustainment capabilities in austere conditions with more rapid technologies able to produce a broader spectrum of components when compared to the current state of the art. Additionally, this effort has potential for applications in the oil and gas industry to enable enhanced facility and equipment sustainment on-site which can allow continued operations and sustained production rates. Follow-on work should focus on certifying materials through process development to produce qualified application-critical weapon system components. REFERENCES: 1. American Society for Testing and Materials, ASTM ISO/ASTM52900-21 Additive Manufacturing – General Principles – Fundamentals and Vocabulary, https://www.astm.org/f3177-21.html (accessed 31 OCT 2022). 2. McCarthy, D.L. & Williams, C.B.. (2012). Creating complex hollow metal geometries using additive manufacturing and electro forming. 23rd Annual International Solid Freeform Fabrication Symposium – An Additive Manufacturing Conference, SFF 2012. 108-120. 3. Rasiya, Gulnaaz & Shukla, Abhinav & Saran, Karan. (2021). Additive Manufacturing-A Review. Materials Today: Proceedings. 47. 4. Benson, J.M.. (2012). Safety considerations when handling metal powders. Journal of the Southern African Institute of Mining and Metallurgy. 112. 563-575. 5. Pauzon, Camille & Hryha, Eduard & Forêt, Pierre & Nyborg, Lars. (2019). Effect of argon and nitrogen atmospheres on the properties of stainless steel 316 L parts produced by laser-powder bed fusion. Materials & Design. 179. 107873. KEYWORDS: additive, manufacturing, laser, electron, beam, metal, powder, expeditionary
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