Effect of laser polishing on fatigue behavior of additively manufactured IN718

Abstract

This study investigates the effect of laser-polishing on the fatigue behavior of Inconel 718 fabricated using laser powder bed fusion process. Three different conditions including as-built and laser-polished using two different process parameters are considered. Uniaxial tension- compression fatigue tests are conducted in strain-controlled mode to examine the fatigue behavior for each condition. In addition, surface roughness measurements and fractography using optical microscopy and porosity measurements using the X-ray computed tomography are also performed for all conditions. The results indicate that laser-polishing alone does not improve fatigue performance, even though it can significantly reduce surface roughness. The beneficial effects of the smoother surfaces may have been countered by the volumetric defects close to the surface induced by laser-polishing. The fracture surfaces also reveal that fatigue cracks are initiated from the defects close to the surface, and therefore, fatigue behavior is not improved.