Within the scope of the presented work the processing of AISI H11 (1.2343 or X37CrMoV5-1) tool steel powder modified by adding carbon black nanoparticles in varying concentrations by means of Laser Metal Deposition (LMD) is extensively investigated. On the basis of single weld track experiments, multi-layered cuboid-shaped samples made out of pure AISI H11 tool steel powder as well as modified tool steel powder mixtures were manufactured by applying various process parameters. The main scientific aim of the investigations was to achieve a basic understanding of the influence of the added carbon black nanoparticles on the resulting sample properties. For that purpose, the generated specimens were first analyzed with respect to relative density, inner defects, microstructure, Vickers hardness and chemical composition. Subsequently, the mechanical properties of post-heat-treated specimens were investigated, with the focus on the yield strength (Y_0.2%), by means of compression tests. We prove that by adding carbon black nanoparticles to the initial AISI H11 powder, the formation of martensitic and bainitic phases, as well as the precipitation of carbides at the grain boundaries, are enhanced. As a result, a significant increase of Vickers hardness and of the compression yield strength by up to 11% can be achieved in comparison to samples made out of the unmodified AISI H11 powder. Furthermore, it can be fundamentally demonstrated that the fabrication of parts with layer-specific variable hardness can be realized by the controlled changing of the powder mixtures used during the layer-by-layer manufacturing approach.

For cost-intensive products like automobiles, clients often wish to personalize their product, what forces the industry to create a large diversity of combinable parts. Additionally, the life cycles of many components become shorter. For highly-stressable parts, which are commonly manufactured by forging, the short changeover cycles result in expensive products, as the costs of tools must be offset by the sale of only a few parts. To reduce the tool cost, new, flexible processes have to be established in tool manufacturing. Laser-based additive manufacturing is noted for its high flexibility; notably, Laser Metal Deposition (LMD) is gaining increasing relevance in research, as it is already used for coating and repairing forming tools, this technology makes it possible to add material onto free-formed surfaces. Therefore, investigations are being conducted to qualify this process to produce forging tools. Due to the thermal processes which are required during additive manufacturing, the microstructure of the material differs from that of wrought material. This, in turn, affects the strategy of post heat treatment in order that the required mechanical properties for tools be attained. Within this manuscript, the influence of additive manufacturing on performance characteristics of hot work tool steel X37CrMoV5-1 (1.2343) is analyzed. To investigate the behavior of additively manufactured material during the process chain of tool manufacturing, properties for different states of a heat treatment are characterized by hardness and strength. It was shown that the strength of the additively manufactured material could be increased compared to wrought material by using a tailored heat treatment. The effects that cause this behavior are investigated by comparing the microstructure at different states of heat treatment.

Mass customization leads to very short product life cycles, so the costs of a tool have to be amortized with a low number of workpieces. Especially for highly loaded tools, like those for forging, that leads to expensive products. Therefore more economical production processes for tool manufacturing have to be investigated. As laser additive manufacturing is already used for the production of moulds for injection moulding, this technology maybe could also improve the forging tool production. Within this paper laser metal deposition, which is industrially used for tool repair, will be investigated for the use in tool manufacturing. Therefore a mechanical characterization of parts built with different laser process parameters out of the hot work tool steel 1.2709 is made by upsetting tests and hardness measurements. So the influence of the additive manufacturing process on the hardness distribution is analysed.