Numerical and experimental investigation on formation of surface structures in laser remelting for additive-manufactured Inconel 718

Abstract

The surface roughness of additive manufactured parts is usually high and not satisfactory for any aimed application. Surface structuring by laser remelting (WaveShape) is a novel laser-based process in which surface structures are mainly created or deleted by reallocation of molten material. Since fundamental aspects of the formation of surface structure in laser remelting are neither fully understood nor completely covered by current models, an enhanced FEM model was developed. Numerical results based on this FEM model suggest that fundamental factors in the formation of surface structures are deformations of the melt pool surface due to changes in the volume of molten material and due to temporal, localized vapor pressure. Based on single track experiments on prepared Inconel 718 specimen, the numerical calculations have been evaluated for a Nd:YAG laser beam source, with a beam diameter of 250 μm, using scan speeds from 25 mm/s to 200 mm/s and a sinusoidal modulation of laser power between 20 W and 225 W. The good agreement of numerical calculations and experimental results indicate that essential effects in surface structure formation were successfully identified. Marangoni convection seems to have virtually no or just a small impact on the formation of surface structures in laser remelting.