Porosity distribution of 316 L stainless steel in laser powder bed fusion additive manufacturing due to spatial variation

Abstract

Laser powder bed fusion (LPBF) is at the forefront of the additive manufacturing industry due to its ability to generate intricate and accurate objects layer-by-layer. However, maintaining low porosity (i.e., minimizing defects) remains a significant challenge. This study investigates the influence of spatial variations on porosity, independent of processing parameters, by fabricating SS316L cubes at various locations on the build platform with both identical and varying processing parameters (laser power and scan speed). Changes in printing location affect the incident angle between the surface normal and the laser, potentially leading to laser spot distortion and altered effective energy input. This, in turn, can influence the porosity of the printed part. Additionally, improper inert gas flow can hinder spatter removal, further increasing porosity. We demonstrate that, regardless of processing parameters, spatial variations on the build platform significantly impact porosity distribution. Our findings, consistent with existing literature, highlight the importance of optimizing both build location and processing parameters to achieve low porosity, particularly at the platform's periphery. By analyzing the optimal build locations and parameter combinations, this work provides valuable insights for LPBF practitioners seeking to minimize porosity and improve printing outcomes at peripheral regions.