Metal Additive Manufacturing Conference 2018

Selective Laser Melting (SLM) is a metal additive manufacturing process widely used in industry for its extraordinary versatility to geometry and minimum waste of material. Mechanical properties of SLM objects depend strongly on the process parameters such as power, scanning speed, hatch space and scanning strategy. Working on these latter parameters, the material can be porous or fully-dense. However, the high thermal gradients which are characteristic of this process induce complex distributions of residual stresses and defects such as micro-crack formation. Both have a negative impact on the geometry and mechanical properties of SLM samples. In the literature, the well-known solution proposed in order to reduce these thermal stresses present in SLM parts is a post-heat treatment. Another possible post-treatment which is mechanical can bypass several of these difficulties. Indeed, the Surface Mechanical Attrition Treatment (SMAT) has a local impact on the sample, thanks to the generation of a nanocrystalline layer on the sample surface provided by severe plastic deformation via multidirectional and random shot impacts. The global mechanical properties of the SLM sample are thus widely improved. The motivation of the present paper is to examine the effect of SMAT on mechanical and surface properties of AISI 316L stainless steel manufactured by SLM. The post-treated samples were characterized by Optical Microscopy (OM), Scanning Electron Microscopy (SEM), surface roughness and micro-hardness measurement techniques. In addition, X-ray diffraction (XRD) method was used to investigate the residual stress present at the surface of the untreated and treated samples.