Structural integrity of direct metal laser sintered parts subjected to thermal and finishing treatments

Direct Metal Laser Sintering (DMLS) is a rapid manufacturing technology that is starting to be used for the manufacturing of functional components. Therefore, properties of DMLS manufactured parts must be carefully analyzed to determine if they satisfy technical requirements under fatigue conditions. In this work, the structural integrity of Maraging Steel, Inconel 718 and CoCr alloy DMLS parts subjected to different thermal and finishing (shot peening and surface polishing) treatments has been characterized in order to determine the optimum stabilization treatment with regard to structural integrity. For this characterization, surface residual stresses, microstructure, porosity and hardness of the parts have been studied. In general, DMLS process origins detrimental surface tensile stresses in Inconel 718 and CoCr alloy components whereas in Maraging Steel parts DMLS results in light surface compressive stresses that improve in general with the application of subsequent thermal and mechanical treatments. Moreover, surface polishing homogenizes the final stresses resulting, besides, in very compressive surface residual stresses.