The effects of geometry and laser power on the porosity and melt pool formation in additively manufactured 316L stainless steel

The present work investigates the effects of geometry and laser power on the porosity and melt pool formation for 316L stainless steel samples fabricated using the laser powder bed fusion (LPBF) technique. Both cylindrical and conical parts with the same heights were processed at a range of laser powers (60–70 W). An analytical model was used to select a suitable laser power, based on the established processing parameters, but also to predict the resultant melt pool dimensions. Based on the combination of experimental work and mathematical modelling, a novel geometrical factor is proposed, which was demonstrated to successfully improve the implemented model. A decrease in melt pool depths towards the building direction was determined in all the printed samples; this was however not predicted by the mathematical model. Furthermore, the variation in heat extraction exhibited by the conical and cylindrical parts allows the correlation between the melt pool dimensions and the geometrical factor. Finally, the influence of conical and cylindrical shapes on part hardness with increasing distance from the build plate was demonstrated; based on this comparison, it was determined that the cone geometries exhibit both a higher Vickers hardness and density.