Multiple-material selective laser melting process development : advancements in the deposition and characterization of multiple-material interfaces

Selective Laser Melting (SLM) is an Additive Manufacturing (AM) technology capable of producing fully dense, high strength parts with complex geometries. However, it currently can only produce parts using a single material. Researchers are working to develop nozzle-based powder deposition mechanisms to enable multiple materials in SLM. This would allow for an added level of design complexity and the matching of material properties to the functional requirements of a part. Nozzle-based powder deposition, however, has several issues that need to be improved and scanning strategies for bonding the different materials together at interfaces need to be developed. Additionally, there is a need for characterization of fabricated multiple-material interfaces to better understand what is occurring during scanning across these boundaries. This dissertation first develops a powder deposition and leveling system used to fix the geometrical inaccuracy and material contamination issues from current iterations of multiple-material deposition systems. Full deposition of a multi-layer, multiple-material powder bed with minimal material contamination is demonstrated. Using the system’s newly established ability, scanning strategies and parameters are developed for fabricating copper-nickel multiple-material parts. Several different lasers are employed to understand the effects of laser power on the quality of bonding at the multiple-material interface. Fabricated parts are characterized using microscopic imaging and energy dispersive spectroscopy techniques to quantify part density, identify porosity formation, and detect if alloying occurred at the multiple-material interface. Large area alloying of copper and nickel is achieved, producing 99.5% dense multiple-material parts. Lastly, a high-level machine design for a next-generation multiple-material SLM machine is provided based on the findings and results of this dissertation’s work to enable and expand subsequent research in the future.