A comprehensive study on the influence of the scan pattern in two porosity levels and surface roughness on the fatigue behavior of laser powder bed fusion manufactured specimens made of steel H13

Abstract

As a developing and immature technique, additive manufacturing (AM) shows some limitations: depending on material and process parameters so far, it usually results in parts with residual porosity, high residual stresses and a surface with a certain level of roughness. Due to its weaknesses and high production costs, AM is more preferably used when the fabricated parts have a high geometry complexity, the material used is very expensive, or the parts can offer additional performance. In order to allocate AM further in industry, a better understanding of the not well-investigated fatigue behavior is necessary. This work focuses on the influences of some general process parameters including laser power, scan speed, scan pattern and postmachining on the resulting fatigue properties of H13 tool steel specimens generated through powder bed fusion (PBF) technique. Results reveal that scan patterns influence fatigue properties by affecting the largest porous defect size and microstructure thus matrix strength. The degree of porosity or roughness resulting from the energy input and postmachining has a significant inferior impact on the fatigue strength. Neither porosity nor tensile properties show a single direct mathematic correlation with the fatigue properties.

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“…In the case of the outer side of the pipe wall for samples 1 and 3, the value of this parameter is above 330 µm, while for sample 2 it is significantly below this value. According to the authors of [42], the higher roughness with the maximal height S z on the underside is caused by the incompletely removed support structure, which is more severe than the intrinsic surface roughness and is the main reason for the crack initiation. The S q parameter, comparing the samples from the inside, remained at the same level and oscillated around the value of 30 µm.…”