Recrystallization behavior and tensile properties of laser metal deposited Inconel 718 upon in-situ ultrasonic impact peening and heat treatment

Abstract

Due to the lack of mechanical compaction, the overall properties of metal parts produced by laser-based additive manufacturing are lower than those of traditional wrought parts. This thus limits the potential of additive manufacturing (AM) techniques in the producing critical structural components. The integration of in-situ ultrasonic impact peening (UIP) with metal AM processes has demonstrated promising results in improving the mechanical properties. In this work, the influence of in-situ layerwise UIP on the recrystallization behavior and tensile properties are investigated for Inconel 718 parts fabricated by the novel hybrid manufacturing process combining laser metal deposition (LMD) and UIP. Also, post heat treatments with different solid solution treatment (ST) temperatures are carried out to investigate the role of heat treatment in material recrystallization, as well as the related mechanical properties. The results demonstrate that a proper combination of in situ UIP and heat treatment significantly facilitates recrystallization refinement and enhances the mechanical properties. Under the optimal 1180 °C ST + age condition, the part manufactured by LMD + UIP hybrid process shows a yield strength (YS) of 977 MPa, ultimate tensile strength (UTS) of 1240 MPa, and tensile modulus of 209 GPa, representing the increases of 28%, 15%, and 67%, respectively, compared with LMD parts made without in-situ UIP.