Research and development in the field of metal-based additive manufacturing are advancing steadily every year. In order to increase the efficiency of powder bed fusion of metals using a laser beam system (PBF LB/M), machine manufacturers have implemented extensive optimizations with regard to the laser systems and build volumes. However, the optimization of metallic powder materials using nanoparticle additives enables an additional improvement of the laser–material interaction. In this work, tool steel 1.2709 powder was coated with silicon carbide (SiC), few-layer graphene (FLG), and iron oxide black (IOB) on a nanometer scale. Subsequently, the feedstock material and the modified powder materials were analyzed concerning the reflectance of the laser radiation and processed by PBF-LB/M in a systematic and consistent procedure to evaluate the impact of the nano-additivation on the process efficiency and mechanical properties. As a result, an increased build rate is achieved, exhibiting a relative density of 99.9% for FLG/1.2709 due to a decreased reflectance of this modified powder material. Furthermore, FLG/1.2709 provides hardness values after precipitation hardening with only aging comparable to the original 1.2709 material and is higher than the SiC- and IOB-coated material. Additionally, the IOB coating tends to promote oxide-formation and lack-of-fusion defects.

Powder bed fusion of metals using a laser beam system (PBF-LB/M) of highly complex and filigree parts made of tool steels is becoming more important for many industrial applications and scientific investigations. To achieve high density and sufficient chemical homogeneity, pre-alloyed gas-atomized spherical powder feedstock is used. For high-performance materials such as tool steels, the number of commercially available starting powders is limited due to the susceptibility to crack formation in carbon-bearing steels. Furthermore, scientific alloy development in combination with gas-atomization is a cost-intensive process which requires high experimental effort. To overcome these drawbacks, this investigation describes the adaption of a hot work tool steel for crack-free PBF-LB/M-fabrication without any preheating as well as an alternative alloying strategy which implies the individual admixing of low-cost aspherical elemental powders and ferroalloy particles with gas-atomized pure iron powder. It is shown that the PBF-LB/M-fabrication of this powder mixture is technically feasible, even though the partly irregular-shaped powder particles reduce the flowability and the laser reflectance compared to a gas-atomized reference powder. Moreover, some high-melting alloying ingredients of the admixed powder remain unmolten within the microstructure. To analyze the laser energy input in detail, the second part of the investigation focuses on the characterization of the individual laser light reflectance of the admixed alloy, the gas-atomized reference powder and the individual alloying elements and ferroalloys.