Parametric Investigations on Continuous Wave Laser Polishing of Laser Directed Energy Deposited SS 316L Bulk Structures

Abstract

Laser Directed Energy Deposition (LDED) based metal additive manufacturing (MAM) built components have higher surface roughness resulting in the need for post-processing treatments. Laser polishing is one of the advanced post-processing techniques gaining significant attention to improve the surface quality of LDED built components. In the present work, the effect of continuous-wave laser polishing on the surface roughness of SS304L specimen manufactured by LDED is investigated. A thermo-physical model is developed to simulate the effect of laser polishing process parameters on the melt pool depth of the LDED built samples. The simulated melt pool depth is compared to experimentally measured melt pool depth and is found to be in good agreement. A maximum reduction of surface roughness from 21.3 µm to 9.0 µm (~ 57%) is achieved with laser polishing and the effect of process parameters on the surface roughness is investigated. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) mapping, and X-ray diffraction (XRD) are used to further characterise the laser polished surface. SEM-EDS analysis shows that the segregation is more evident in laser polished samples and XRD results show no extra peak generation due to laser polishing. The study paves a way to understand the effect of laser polishing on LDED built SS 304L structures.