Spattering effects during selective laser melting

Additive manufacturing using preplaced powder became a widely used processing method during the last few years to build complex and precise structures. The laser beam is often used as a heat source to selectively melt the powder and create the structure layer by layer. However, during the processing, imperfections can occur. The spattering, accumulation of powder particles, and denudation effects lead to a redistribution of the powder in the powder bed, a loss of powder, and agglomerations. These effects can alter the processing of the subsequent tracks and layers. On the one hand, the track dimensions can vary by varied amounts of available powder. On the other hand, the process can become unstable due to different powder surface geometries, agglomerates, and the resulting variation of energy absorption. Therefore, this work aims to explain spattering effects during powder-bed processing, which can be used for modification of the processing parameters for spatter prevention. High-speed-imaging was used to record the powder and spatter behavior during the laser powder-bed processing from different angles. It was observed that different kinds of spattering can occur. Melt pool spattering occurs due to melt instabilities, while powder particles seem to be accelerated by vapor induced gas movement, pressure waves, and the gas flow induced by the Bernoulli-effect.