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The layer-by-layer principle of additive manufacturing technology laser powder bed fusion (LPBF) opens up completely new possibilities in the design and manufacturing of lightweight and efficient gear components. For example, integration of contour conform cooling and lubrication channels into gear components can increase their service life and reduce lubricant consumption. Steels for quenching and tempering and case hardening steels are commonly used materials for gear components. However, the availability of these alloys for LPBF processing is still limited. In particular, the 30CrNiMo8 steel for quenching and tempering is frequently used for gear wheels. This specific alloy is largely unknown regarding LPBF processing and remains challenging, because of its susceptibility to cracking and the high temperature gradients that occur during the LPBF process. Therefore, this study focuses on the LPBF processing of 30CrNiMo8 powder material including process parameter evaluation and material characterization. Additionally, effects of the heat treatment on the resulting microstructure and mechanical properties were investigated. Within this study the 30CrNiMo8 has been processed successfully with a density of well above 99.5% leading to promising mechanical properties. A more homogenous microstructure has been achieved with quenching and tempering, compared to the as-build state.

Purpose For geometries exhibiting overhanging surfaces, support structures are needed to dissipate process heat and to minimize geometrical distortions attributed to internal stresses. The use of support structures is often time- and cost-consuming. For this reason, this study aims to propose an approach which minimizes the use of such structures. Design/methodology/approach For minimizing the use of support structures, process parameters in combination with a contour-like exposure strategy are developed to realize support-less overhanging structures of less than 35°. These parameters are implemented in a shell-core strategy, which follows the idea of applying different processing strategies to the critical (overhanging) shell and the uncritical core of the part. Thereby, the core is processed with standard parameters, aiming a dense material. On the critical shell, optimized processing parameters are applied, reaching good results in terms of surface quality, especially at extreme overhang situations. Findings The results show that the selective laser melting (SLM) technology is able to realize support-less overhanging surfaces by choosing suitable scan strategies and process parameters. Particularly good results are always obtained when the exposure direction of the shell is parallel to the contour of the sample. Originality/value The validity of the results is demonstrated through the successful reproduction of the build strategy on two commercial SLM machines, reaching support-free builds of surfaces with an angle to the horizontal of less than or equal to 30°.

To achieve a certain visual quality or acceptable surface appearance in injection-molded components, a higher mold surface temperature is needed. In order to achieve this, injection molds can be dynamically tempered by integrating an active heating and cooling process inside the mold halves. This heating and cooling of the mold halves becomes more efficient when the temperature change occurs closer to the mold surface. Complex channels that carry cold or hot liquids can be manufactured close to the mold surface by using the layer by layer principle of additive manufacturing. Laser powder bed fusion (L-PBF), as an additive manufacturing process, has special advantages; in particular, so-called hybrid tools can be manufactured. For example, complex tool inserts with conformal cooling channels can be additively built on simple, machined baseplates. This paper outlines the thermal simulation carried out to optimize the injection molding process by use of dynamic conformal cooling. Based on the results of this simulation, a mold with conformal cooling channels was designed and additively manufactured in maraging steel (1.2709) and then experimentally tested.

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