Nanoparticle-Coated X2CrNiMo17-12-2 Powder for Additive Manufacturing - Part I: Surface, Flowability, and Optical Properties of SiC, Si, and Si3N4 Coated Metal Powders

The coating of metal powders with nanoparticles renders the possibility to improve powder bed fusion of metals using a laser beams (PBF-LB/M) from the powder side of view. The literature indicates that nanoparticle coatings not only improve mechanical properties of final parts but also decrease manufacturing costs through higher process efficiencies. Herein, coatings of X2CrNiMo17-12-2 with silicon, silicon carbide, and silicon nitride are presented using different particle sizes of 65-200 nm and different coating surface coverages, which lead to homogeneous and stable coatings. A scale-up and process parameter variations demonstrate the reproducibility of the process and also the relevance of the used processes for commercial applications. The main finding of this study is that the surface roughness due to nanoparticle coating is related directly to the powder flowability measured with the ring shear tester as a property function. In addition, for similar coating structures, the nanoparticle material influences the flowability due to the nature of its Hamaker constant. However, the reflectance of coated metal powders is dependent on the reflection of the coating material, the induced surface structure, and the amount of coated particles. These relationships might be transferred to improvements in the PBF-LB/M process.