SusChEM: Sustainable material use in laser deposition: integrating experimental design, environmental impact assessment and economic evaluation

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1605392 Schoebubg, Julie M.Conventional methods used to fabricate metallic components generally require casting or wrought fabrication processes such as extrusion or forging. Secondary machining steps are generally necessary in order to achieve specified surface finish, dimensional accuracy and geometrical complexity. But machining wastes both material, i.e., the scrap material removed from the bulk part (machining chips), and energy, rendering conventional methods highly inefficient from a sustainability perspective. As an alternative, direct metal deposition techniques are being explored, which create solid metal parts by melting metal powder and depositing material only where it is wanted, thus fabricating the component by adding, rather than subtracting material. This change in fabrication strategy is intended to inherently reduce both energy requirements and material waste by avoiding (or reducing) the extent of secondary machining required. However, the actual deposition efficiency, i.e., fraction of feedstock material that actually becomes part of the consolidated component, has been demonstrated to be as low as ~5%. In practice, the remainder of the powder is generally not reused, and becomes waste (waste powder), just like the machining chips. Consequently, these direct metal deposition processes also present critical issues in terms of sustainability. This research program has three primary research objectives: to formulate a quantitative assessment framework for environmental impact assessment and economic evaluation of direct metal deposition technologies, to utilize this framework to guide the experimental design space for utilizing waste powder and machining chips as alternative feedstock materials in direct metal deposition, and to implement the experimental design, including carefully controlled component fabrication, coupled with in-depth characterization and testing. This research incorporates various assessment and evaluation tools into a quantitative assessment framework that captures the experimental variables associated with direct metal deposition, especially when utilizing alternative feedstock materials. This framework will be formulated so that it is integrated with and therefore guides the experimental design space, rather than being carried out after all the experimental parameters have been rigidly defined, as is the current norm for assessment studies. Overall, the research will advance the understanding of the performance-sustainability-economics trade-off space for direct metal deposition. Direct metal deposition is a relatively new technology that is promoted to be cost effective and sustainable, due to its ability to create parts through addition, rather than subtraction, of material. Yet the process currently has limitations in materials utilization, but moreover appears to be sufficiently robust to potentially overcome these limitations through the utilization of alternative feedstock materials. From a broad perspective, these topics present a foundational opportunity to highlight trade-offs between performance, sustainability and economics, and furthermore to promote the incorporation of sustainability and economic assessment early in the design process.