Influence of in-situ hammering on microstructural, mechanical and residual stress behaviour of inconel 718 during wire arc additive manufacturing

Metal additive manufacturing primarily produces functional metal parts in various industries. The direct energy deposition (DED) method involves melting wire-shaped raw material to create parts. Wire arc additive manufacturing (WAAM) is a DED process that makes large components. However, residual stress remains a significant challenge, especially in the WAAM of Inconel 718 components. To minimize this problem, this study introduces and investigates the influence of in-situ hammering (IsH) of WAAMed IN718 specimens. In this research work, the mechanical properties and microstructure characterization of IN718 were methodically investigated by X-ray diffraction, optical microscope, micro-hardness and compression testing of both as-deposited (AD) and IsH specimens. The results showed that IsH specimens produced small, uniform grains due to plastic deformation. In contrast, AD specimens produced large and columnar grains along the deposition direction due to thermal gradients and solidification patterns. Also, fewer but larger grain boundaries appear in AD samples, whereas in IsH samples, grain boundaries appear more numerous and finer. The IsH component’s overall compressive strength, yield stress and micro-hardness reached 1414.2 MPa, 718.1 MPa and 231.23 ± 1 HV, respectively, 2.1%, 42.02% and 3.2% higher than the AD component. Also, the IsH process reduces the micro-strain and compressive residual stress by 52.6% and 44.1%, respectively, compared to the AD component. This improvement in microstructure characterization and mechanical properties suggests that IsH is a promising in-process solution that will help improve the reliability and lifecycle of WAAM-manufactured Inconel 718 components, making it an essential choice for aerospace and high-temperature applications.