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Abstract:

Selective Laser Melting (SLM) is an Additive Ma nufacturing technique in which a product is built up in a layer-by-layer fashion, by melting me tal powder particles using a high power laser. It enables the production of complex threedimens ional parts with high density. As SLM is a re latively new manufacturing process, many obstacles have to be overcome and the goal of this wor k is to address some of the process ’ limitations and mainly to broaden the mate rials palette. Four different mater ials, divided in two material groups were pro cessed in this work. The first part desc ribes the work on two aluminum alloys, a cast aluminum alloy A360.0 and a wrough t aluminum alloy 7075. The second part handles the process capabilities of two types of tool st eel: a low-carbon maraging steel 18Ni300, and a high-carbon M2 High Speed Steel.The primary goal of this thesis is to p roduce nearly-fully dense parts in all f our materials. Along the way, barriers need t o be overcome that characterize the SLM process, b ut prohibit it from reaching a higher technology r eadiness level, like thermal stresses, cracks and poor dimensional accuracy. Cracks a re eliminated by the use of either baseplate pre-heating, or addition of alloying pow ders (e.g. silicon), depending on the or igin of the crack formation. The influence of ¨the composition, size and morphology of base ¨powder material is shown to be detrimental f or the final part quality. After proper powder selection, the production of nearly-fu ll dense parts can be achieved after opt imization of scan parameters like laser power , scan speed, scan spacing and layer thicknes s. Laser re-melting as an additional scan str ategy can increase the part density and impro ve the top surface roughness significantly.Furthermore, a preliminary experiment of singl e track scans offers a great amount of information and defines a process window, in which a stable melt pool is formed. Mater ial characterization in terms of mechanical p roperties and microstructure are conducted to ¨compare the quality of as-built SLM parts to conv entionally produced and heat treated parts.