Residual Stress Analysis of Additively Manufactured and Post Processed Inconel 718

The aim of the present work is to assess the impact of postprocessing on the residual stress distribution of additively manufactured Inconel 718 alloy. The samples were manufactured through laser–powder–bed–fusion (LPBF) and subjected to a combination of heat treatments and shot peening. The microstructural changes were studied using SEM/EDS and the residual stress profile was measured in all the conditions using XRD diffraction technique. It was seen that residual stress present in the as built condition was tensile in nature, whereas the postprocessed samples were found to contain compressive stresses. The tensile residual stress is primarily caused by the temperature gradients arising due to the repeated heating—cooling cycle in the printing process. This stress becomes compressive stress when the samples are subjected to shot peening, due to the strain hardened layers introduced by the impact of the repeated bombardment of balls. Additionally, the presence of multiple phases in the heat-treated samples also contribute to the overall stress depths.