Experimental and analytical investigations of the removal of spatters by various process gases during the powder bed fusion of metals using a laser beam

The powder bed fusion of metals using a laser beam (PBF-LB/M) is increasingly being utilized in industrial applications. This is due to several advantages over conventional manufacturing processes when it comes to the fabrication of complex part designs. However, the process still poses various challenges that have to be overcome. One of these challenges is the formation of a significant amount of spatters and fumes. These could attenuate the laser beam or decrease the powder reusability. To lower their negative impact on the process and the mechanical properties of the parts, a process gas flow is used in PBF-LB/M to remove these by-products from the processing zone. This study was, therefore, dedicated to investigating the potential of various gases on the removal of spatters. The focus was placed on argon, helium, and their mixtures. After theoretical considerations determining the range of applicable gas flow velocities, the experimental results unveiled the real spread of spatters over the powder bed and their characteristics. Whilst the removal of spatters was found to be worse for an argon-helium gas mixture at comparable gas flow velocities, increasing the velocity turned out to be a proper measure to enhance the removal for low-density gases. At this flow condition, the use of the argon-helium gas mixture led to a similar removal of spatters and the creation of a lower spatter mass in total (reduced to 40%) compared to argon.