Evolution of residual stress behavior in selective laser melting (SLM) of 316L stainless steel through preheating and in-situ re-scanning techniques

The premature fractures, cracks, distortions, and delamination in selective laser melting manufactured components are among the most prominent challenges. These issues in selective laser melting manufactured components restrict their widespread application. Residual stresses are among the most common reasons for these behaviors. Post processing techniques are therefore used for most of the selective laser melting fabricated components to either eliminate or decrease these stresses. However, this increases the production time and fabrication costs. Therefore, in process techniques to reduce these residual stresses are of paramount importance in promoting the largescale production of metallic components. In this paper, a finite element method-based investigation of preheating and in-situ rescanning techniques during selective laser melting of 316L stainless steel is presented. The influence of various preheating temperatures on the final residual stress profile was observed. Similarly, the variations in residual stresses with different rescanning parameters were also investigated. Both baseplate and powder bed preheating procedures were observed to have considerable effects on the residual stresses. The residual stresses were significantly decreased with increasing preheating temperatures. Baseplate and powder bed preheating at 400 °C were observed to have decreased the residual stresses from 353.57 MPa (stress values without preheating or rescanning) to 27 MPa and 30 MPa, respectively. In-situ rescanning was also observed to be beneficial in decreasing the stresses in SLM fabricated components. However, their influence is relatively smaller in comparison with the preheating. No significant influence of rescanning on the stress distribution was also observed.