Process stability and limits of agglomerating 316L powder in laser powder bed fusion of metals

Process stability and maximum productivity are fundamental requirements for laser powder bed fusion of metals (PBF-LB\ M). The influence of particle size distribution and process parameters have been investigated in many studies. However, these findings are limited to spreadable powder. For agglomerating powders, due to a large number of fine particles, recoating is not possible with a conventional recoater. To overcome this obstacle, an ultrasonically excited recoating system was developed, in previous work. The processing of such powder is desirable, as the yield of atomization can be increased by about 24 %. To evaluate the process stability and limits, single beads and volume bodies were manufactured. A stable process window, reaching a high relative density, was determined. A critical influence of the O2 concentration in the build chamber and the vibration amplitude of the ultrasonic recoater was found. The productivity is limited by the process induced powder-movement, due to the formation of a powder wall.