PSI - Issue 54

Daniel F.O. Braga et al. / Procedia Structural Integrity 54 (2024) 568–574

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2 Daniel F.O. Braga et al. / Structural Integrity Procedia 00 (2023) 000–000 opportunity to bridge the gap between intricate, highly customized parts and production efficiency, ensuring that the future of metal AM not only unlocks unbounded creative design possibilities but also accelerates manufacturing processes, addressing the growing demand for cost-effective, high-quality components across diverse industries.

Nomenclature CCD Central Composite Design DoE Design of Experiments DED Direct Energy Deposition DIC Digital Image Correlation LMD Laser Melting Deposition SLM Selective Laser Melting UTS Ultimate Tensile Strength

Graf et al. (2015), manufactured Inconel 718 turbine blades, with a combined process of SLM and LMD, demonstrating the feasibility of this production approach. Prior to demonstrator manufacturing, microstruc tural analysis was conducted in Ti-6Al-4V, manufactured with the same apporach, showing good metallur gical bonding between LMD single layers and to the SLM part, with no visible cracks at the boundary and in the adjacent microstructure. The combined process chain, resulted in a significant decrease in manufac turing time ( ≈ 61.4 %), but temperature and part cooling control during LMD process was shown to be challenging regarding melt pool dimensions and process stability. As advantages of employing this manu facturing approach, the authors list, the part complexity flexibility, with complexity provided by the SLM process, the ability to employ dissimilar material manufacturing through LMD and the increase in build rate, which improves production scale. Beyond manufacturing of high-low geometric complexity parts, Petrat et al. (2016) demonstrated the use of this approach to repair SLM components through LMD, and Petrat et al. (2018) demonstrated the integration of electronics onto components manufactured with this hybrid SLM, LMD approach. Uhlmann et al. (2019) studied Inconel 718 manufactured through SLM and LMD, and the effect of heat treatment on these hybrid components, as a way of mitigating the dissimilarities due to the different thermal signatures of SLM and LMD. The uniformity of the structures that underwent heat treatment improved, but some microstructure dissimilarity induced by each additive manufacturing process still remains. Metal AM adoption has expanded significantly with the development of AM processes, materials, inspec tion methods, and further knowledge on the properties of components manufactured with these processes. Vafadar et al. (2021) reviews metal AM and lists the adoption by sector, where it is stated that industrial machines makes up 20 % of the adoption. Within those, tools and moulds are a significant application and have led to significant research effort on tool steel AM. Braga et al. (2021) demonstrated LMD as a tool die repair process by depositing H13 tool steel on an H13 tool steel substrate. The deposited material showed significant increase in hardness and wear resistance, regarding the substrate material, due to formation of a finer grain structure and an α ’-martensitic matrix during the solidification process. Mazur et al. (2016) stud ied the SLM H13 tool steel for injection mould tooling with conformal cooling channels and internal lattice structures. These tools are shown to have improved thermal management and reduced cycle-times, however present some challenges in manufacturing. A compromise between dimensional accuracy and porosity was found when process parameters resulted in energy densities of 80 J/mm 3 and laser power of 175 W. Design considerations for trusses and cooling channels are also given, such as the use self-supporting profile cooling channels in detriment of standard circular profiles which result in higher dimensional accuracy, especially where the arc section approaches horizontal inclination. This work uses Design of Experiments (DoE) to study hybrid SLM LMD manufacturing process and optimize it towards tensile strength. The ultimate goal is to enable the development of high demanding