Selective laser melting (SLM) of AISI 316L—impact of laser power, layer thickness, and hatch spacing on roughness, density, and microhardness at constant input energy density

TLDR

Selective laser melting (SLM) process parameters significantly influence the resulting workpiece characteristics. This study investigates the effect of varying laser power, layer thickness, and hatch spacing on AISI 316L parts produced by SLM. By adjusting scanning speed to keep input energy density constant, the authors evaluated the impact of laser power, layer thickness, and hatch spacing at two energy density levels. The results show that constant energy density combined with varying laser parameters causes substantial changes in roughness, density, and microhardness, and that selecting optimal laser power, layer thickness, and hatch spacing can improve density and microhardness, with microhardness correlating with relative density up to 99.9%.

Abstract

Abstract In selective laser melting (SLM) the variation of process parameters significantly impacts the resulting workpiece characteristics. In this study, AISI 316L was manufactured by SLM with varying laser power, layer thickness, and hatch spacing. Contrary to most studies, the input energy density was kept constant for all variations by adjusting the scanning speed. The varied parameters were evaluated at two different input energy densities. The investigations reveal that a constant energy density with varying laser parameters results into considerable differences of the workpieces’ roughness, density, and microhardness. The density and the microhardness of the manufactured components can be improved by selecting appropriate parameters of the laser power, the layer thickness, and the hatch spacing. For this reason, the input energy density alone is no indicator for the resulting workpiece characteristics, but rather the ratio of scanning speed, layer thickness, or hatch spacing to laser power. Furthermore, it was found that the microhardness of an additively manufactured material correlates with its relative density. In the parameter study presented in this paper, relative densities of the additively manufactured workpieces of up to 99.9% were achieved.