The effect of powder reuse on the surface chemical composition of the Scalmalloy powder in Powder Bed Fusion – Laser Beam process

The powder quality is one of the main factors to be considered in laser powder bedfusion (PBF-LB/M) production closely connected with the performance of the finalcomponent. Only powders with spherical particles, a low percentage of satellites, anarrow particle size distribution, controlled internal defects and a strongly limitedsurface oxide layer are acceptable for PBF-LB/M production. Gas atomisation is themain production method that permits to achieve the restrictive standards of thePBF-LB/M powder; however, it is energy-intensive and characterised by limited pro-ductivity. These considerations justify the key role of the reuse of the unmeltedmetal powder in obtaining a more sustainable PBF-LB/M process. Nevertheless, thereuse of the powder leads to significant changes in the particle morphology, particlesize distribution and surface chemical composition, which can compromise the bulkproperties. Powder surface oxide is one of the most impactful problems for the PBF-LB/M production, and Al-based alloys are particularly prone to this phenomenon.With the aim to study the effect of the powder reuse, a surface chemical analysis ongas atomised Scalmalloy powder was performed through the X-ray photoelectronspectroscopy investigation before and after seven jobs with 32 h as overall buildtime. Results obtained for virgin and recycled Scalmalloy powders revealed remark-able differences in depth and composition of the surface oxide layer. The 57%increase in the oxide layer thickness and the formation of carbides during PBF-LB/Mproduction can have harmful effects on bulk properties.