Abstract
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.
Highlights
The particle size distribution (PSD) of the feedstock powder exhibited a monomodal distribution with a x50,3 of 31.8 μm, a small span of 0.94
In contrast to the microstructures obtained after solution annealing and precipitation hardening, the fine cellular microstructure previously formed during the PBF-LB/M densification is still present after aging (490 ◦ C, 6 h) for all investigated samples (Figure 14e–h)
The subsequent examination of the relative density, build rate, hardness, and microstructure under consideration of different heat-treatment methodologies allows the determination of production efficiency
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The modification of commercially available powder feedstocks by nanoparticle additivation has been addressed multiple times in the scientific literature, as depicted This enables more efficient process control and can promote the processing of dense and defect-free components with improved mechanical properties. Sehrt et al [13] processed Al2 O3 nanoparticles on feedstock material tool steel (1.2709) and Hastelloy X (2.4665) and investigated the melt pool dynamics and microstructural properties. Both nanocomposites show a significant improvement of mechanical properties. By applying 0.1 wt.% of carbon nanoparticles on the surface of pure copper particles, a relative density of 98% could be achieved while using more efficient process parameters due to an increased absorption. Mechanical properties, such as tensile strength and YS, could be increased by 56 MPa and 79 MPa, respectively
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