Laser Finishing of the Multi-Scale Surface Structure of Additive Manufactured Parts

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The goal of this research is to improve surface finish and mechanical properties (e.g. fatigue life) of additively manufactured metallic parts through the application of laser remelting. The crucial need for research on improving the surface finish of additively manufactured parts and characterizing the impact of the process on part performance has been identified by several technology roadmaps published in 2015 and 2016. The laser remelting process on which this proposal is focused presents significant, yet unexplored opportunities for smoothing and functionally improving additively manufactured parts, and it can be integrated into existing laser-based additive manufacturing equipment creating a process that improves the as-built surface finish.Both the primary powder-based laser additive manufacturing process and the secondary laser remelting process (to fully incorporate partially melted powder particles, reduce porosity, and smooth the surface) will be studied in this integrated project. The collaborative structure of the proposed research brings together expertise in the primary build process (University of Bremen, Germany) and expertise in the laser finishing process (University of Wisconsin-Madison, USA). The new understanding of surface topography and property outcomes will expand the potential of additive manufacturing by reducing the manufacturing limitations.The scientific contribution of this work can be summarized into three parts: (1) providing fundamental understanding and description of the multi-scale surface topography created by powder-bed laser additive manufacturing and how this relates to the process parameters and feedstock, (2) understanding the physical phenomena behind laser remelting of these surfaces for smoothing and creating appropriate models, and (3) understanding the impact that this smoothing has on the performance of the surface as compared to the as-built part (e.g. fatigue life).The proposed research will contribute to the movement toward mass customization by giving designers a new level of freedom to create unique, customer specific, high quality parts at a reasonable cost. This project achieves this by focusing on laser-based processes that can build a part and finish it in the same machine, opening up opportunities for customized manufacturing of high performance products. The fundamental models created will form a foundation for pursuing similar improvements in the additive manufacturing of polymeric parts, directed powder methods, and multi-material processes. These models can also be fed back upstream to improve additive manufacturing design software such that design engineers will have more awareness of and control over the final outcomes. Further societal impact will result from, integrating the knowledge gained in this project into undergraduate and graduate courses, training the future workforce, increasing the participation of students from underrepresented groups, and outreach to the public.