Enhancing fatigue life of additive manufactured parts with electrospark deposition post-processing

Abstract

Metal additive manufacturing processes allow for the production of highly dense parts with increased geometric freedom and less waste than traditional manufacturing techniques. However, one of the biggest challenges in using these parts is the relatively high surface roughness inherent to the manufacturing process. This roughness negatively affects fatigue properties and necessitates the use of post-processing surface treatments. Several methods are presented for improving local surface properties of laser powder bed fusion parts using electrospark deposition (ESD), hammer peening and heat-treatment processes. An optimized surface roughness reduction of 82% and near-surface hardness increase of 85% is obtained. Post-processed Hastelloy X parts reach > 107 cycles during fatigue testing at 350 MPa, in comparison to failure at 105 cycles in the as-built condition. The improvement in mechanical properties obtained with a combined ESD and peening process shows potential for the selective enhancement of critical surface regions in additive manufactured parts.