Ultrasonic micro-forging post-treatment assisted laser directed energy deposition approach to manufacture high-strength Hastelloy X superalloy

Abstract To broaden the applications of Hastelloy X superalloy manufactured by laser directed energy deposition (DED-L), ultrasonic micro-forge treatment (UMT) assisted DED-L was developed to print Hastelloy X components with improved mechanical properties. In this study, the residual stress and mechanical properties of the non-UMT- and UMT-treated samples are compared, and the microstructure was examined to reveal the root cause. During additive manufacturing, the sample structure recrystallized from columnar grains to equiaxial grains, which exhibited much finer structures after UMT. The impact toughness, ductility, tensile strength, and microhardness of the superalloy increased after UMT. During the UMT process, the dislocation pileups appeared and offered hinderance to the dislocations moving within it, thereby improving the mechanical strengthening of the Hastelloy X superalloy.