Experimental analysis of spatter generation and melt-pool behavior during the powder bed laser beam melting process

The experimental analysis of spatter formation was carried out on an instrumented SLM set-up allowing the quantification of spatter ejections and possible correlation with melt-pool behavior. Considering nearly similar SLM conditions than those carried out on SLM machines, an increase of large spatters (> 80 mu m) with volume energy density (VED) was clearly demonstrated on a 316L stainless steel, which was attributed to the recoil pressure applied on the melt-pool by the metal vaporization and the resulting high velocity vapor plume. In a second step, much lower spattering was shown on Al-12Si powder beds than on 316L ones. Fast camera analysis of powder beds indicated that droplet formation was mostly initiated in the powder-bed near the melt-pool interface. On Al-12 Si alloys, such droplets were directly incorporated in the MP without being ejected upwards as spatters like on 316L. Last, it was shown that a strong reduction of spattering was possible even on 316L, with the use of low VED combined with larger spots (approximate to 0.5 mm), allowing to melt sufficiently deep layers in conduction regime and ensure adequate dilution between layers.