Development of an ultrasonically excited recoating process in laser powder bed fusion to process non-spreadable 316L powder

Part quality in laser powder bed fusion is influenced by the uniformity and density of the powder layer. As a result, requirements for the powder regarding spreadability and flowability are restrictive. Many researchers reported recoating defects for cohesive and agglomerating powders. However, the processing of such powders is highly desirable since e.g. surface roughness can be reduced. Therefore, we propose a novel ultrasonically excited recoater system to process such powder. In order to qualify the new recoater system, five different geometries with various amplitudes and recoating velocities were evaluated and compared to a conventional system. The defect rate, determined with a camera and AI-based analysis, the deposited mass and segregation along the recoated distance and the powder layer density of the resulting powder bed were analyzed. A process window and optimal geometry could be identified. It was possible to reduce segregation to a minimum, while maintaining a smooth, dense layer.