Determination of residual stress for Inconel 718 samples fabricated through different scanning strategies in selective laser melting

Abstract

Selective laser melting (SLM) technique is a widely adopted fabrication procedure in metal additive manufacturing. One of the reasons for the extensive usage of SLM is the material freedom which it offers; therefore, Nickel alloy IN718 metal components were fabricated for this study. However, like in any manufacturing process, physical defects are evident in SLM fabricated parts. The origin of these defects can be attributed to the variation in the process parameters. For any physical components fabricated using the SLM technique, various stresses are developed due to the thermal gradients during the fabrication process. The developed stresses are hence termed as residual stresses. These stresses can be detrimental to the mechanical properties of the part. Residual stresses lead to warping of the part during the fabrication process, thereby leading to failure of the component. Therefore, it is necessary to investigate the effect of change in process parameters on the residual stresses. Although each process parameter has its effect on the overall properties and residual stresses, to limit the scope of the study, the scan strategy is the only parameter that is varied. Scan strategies adopted here are checkered, stripes scan strategy, FO1, and customized scan strategy, where the angle between the consecutive layers has been changed consistently at an angle of 67° . In this study, the residual stresses are measured using the contour deflection method. Based on the results, various levels of residual stresses were observed for different scan strategies. It was concluded that a more uniform scan strategy results in less residual stress.