Electrical Current-Assisted Low-Plasticity Burnishing of Inconel 718 Built by Laser Powder Bed Fusion: Surface Integrity and Fatigue Life Analysis

Low-plasticity burnishing (LPB) is usually used for finishing of material to enhance service performance by improving the roughness and inducing compressive residual stress to surface and underneath layers. However, processing of nickel-based superalloys by burnishing is usually challenging because of resistance of material against plastic deformation. Therefore, the material should be burnished following multiple pass that results increase of production time. In the present work, a plausible solution, namely electric-current-assisted burnishing (ECAB), is introduced to be used as post-treatment for Inconel 718 material produced by laser powder bed fusion process. The surface integrity aspects, i.e., roughness, hardness, residual stress, microstructure change and fatigue life after LPB and ECAB under different pass number, were compared by as-built material to identify the efficiency of the introduced methodology. The results indicated that for conventionally burnished sample, after second pass, no more improvement in fatigue life of the sample is observed and even it decreases at third pass. On the other hand, it was found that for the ECABed samples, after only a single pass, the fatigue life and surface integrity aspects reach maximum values of conventionally burnished sample implying ECAB causes reduction of production time to one third. Moreover, it was found that in contrast to conventional burnishing process, in ECAB process, due to electroplasticity effect, contribution of pass number in improvement of fatigue life and surface integrity will be more substantial where continuous enhancement is seen up to three pass. Current is applied to the process, the pass number is more influential fatigue life and surface integrity aspects are.