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Dissertation
Year: 2022 Publisher: Liège Université de Liège (ULiège)
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Laser Powder Bed Fusion (LPBF) process allows powders of different materials to be selectively melted together. However, the unsintered powders are mixed together and therefore cannot be used anymore. To reduce waste, a method to separate powders presents a great interest. The goal of this thesis is to find and design a method to separate two powder mixes: 316L/CuCrZr and M300/CuCrZr. The difficulty lies in similar powder properties, such as density, particle size distribution and electrical resistivity. After discussion on different separation methods, the focus will be on magnetic separation process. For the 316L/CuCrZr couple, it appears that 316L shows a ferromagnetic behaviour only for smallest particles. This heterogeneous magnetic property makes a separation by magnetism difficult to achieve. On the other side, since M300 presents strong ferromagnetic behaviour, while CuCrZr a non-magnetic one, a magnetic-based separation is considered for this couple. A prototype is developed, based on free-fall separation and powered by an ultrasonic device. Some issues are raised and system parameters are discussed to find an optimal solution for the separation process.
powder --- aerosint --- metal --- maraging --- M300 --- 316L --- CuCrZr --- magnetic separation --- additive manufacturing --- powder bed fusion --- laser --- Ingénierie, informatique & technologie > Ingénierie civile
Dissertation
Year: 2022 Publisher: Liège Université de Liège (ULiège)
Abstract | Keywords | Export | Availability | Bookmark
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Additive manufacturing, or 3D printing, has largely developed in the last 5-10 years and a lot of companies were created by coming up with ingenious and new processes, Aerosint is one of them. Aerosint has developed the first Laser Powder Bed Fusion printing head that allows to print two materials at the same time. In this work, some thermal properties of pure and bi-material parts are studied. The pure metallic parts are made out of CuCrZr and Maraging steel M300 and the bi-metallic parts are made out of a both. The evolution of the thermal diffusivity is studied for the as built printed parts and for two aging treatments, one at 520°C during 45 min and one at 520°C during 6h. Then the augmentation in diffusivity induced by the addition of copper on the steel is studied. After that a measurement of the evolution of the contact resistance between the two metals is led. Finally, a short study of the evolution of the grain size in the copper alloy is done thanks to the ASTM E112 standard. The results show that for the CuCrZr the diffusivity is 3 times higher after 45 min of aging and stays stable after (from 30 to around 90 mm^2/s). For the M300 the diffusivity is multiplied by 1.1 for a heat treatment of 45 min and by 1.3 for a heat treatment of 6 hours (from 4.5 to 5.5 mm^2/s to 6.5 mm^2/s), so for the steel alloy the aging does not do much, at least in terms of diffusivity. The bi-material part has around 1.8 times better diffusivity than the steel alone for the as-built part and for the heat treated parts it is around 2.3 times better. The contact resistance drops down to around 10% of its as built value after 45 min of heat treatment and then goes up again to around 15 of its as built value after 6h of heat treatment (from 1.5 x 10^(−5) to 1.7 x 10^(−6) m^2K/W). The use of ASTM E112 says that the grain size does not change during the heat treatments and stays at around 6.
Additive manufacturing --- Aerosint --- Bi-material --- CuCrZr --- M300 --- Thermal diffusivity --- Thermal contact resistance --- Ingénierie, informatique & technologie > Ingénierie chimique
Dissertation
Year: 2022 Publisher: Liège Université de Liège (ULiège)
Abstract | Keywords | Export | Availability | Bookmark
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This master thesis consists of developing an automated powder transfer system for industrial additive manufacturing printers. Current systems only allow a limited amount of powder to be loaded into additive manufacturing printers. Therefore, it is necessary to interrupt the additive manufacturing process so that an operator can reload the powder in the printers. This interruption is counterproductive and can also impact the quality of the printed part as it disturbs its thermal balance. A system will therefore be developed to load the powder in an automated manner.
3D printers --- Sizing --- Additive manufacturing --- Powder transfer --- Transfer system --- Aerosint --- Automated transfer --- Sizing pneumatic system --- Pneumatic conveying --- Dilute phase --- Dense phase --- Feeding --- Cyclone --- Settling chamber --- Filtration --- Blower --- Saltation velocity --- Solid loading ratio --- Stairmand geometry --- Tri-clamp --- Flow simulation --- Particles simulation --- Grafcet --- Bosch structure --- Pipeline pressure drop --- Filtration pressure drop --- pressure drop --- Prusa --- Mechanical --- Engineering --- Solidworks --- Ingénierie, informatique & technologie > Ingénierie mécanique
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