Enhancement of tensile properties and isotropy of wire arc additive manufactured alloy 625 via thermomechanical process

Abstract

We developed a wire-arc additive manufacturing system and designed the thermomechanical process to enhanced the mechanical properties of Inconel 625 deposit. Thin-wall deposits were built using various scan speeds, and the obtained microstructure was predicted via thermal-history simulations. The microstructures of the thin-wall deposits were largely identical regardless of the process parameters. Furthermore, thick-wall deposits were manufactured using the process parameters established from the thin-wall manufacturing process. Multidirectional hot forging and aging treatments were applied to improve the tensile properties and isotropy. Hot forging dynamically recrystallized the microstructure. As the forging ratio and number of cycles increased, the grain size and anisotropy of the tensile properties decreased. Furthermore, as aging treatment was performed at 650 °C for 12 h after forging, the γ’’ phase was not precipitated effectively; however, in the case of aging for 24 h, sufficient γ’’ phases were formed, enhancing the tensile properties of the deposits. Thus, we obtained wire-arc additive manufactured deposits with excellent tensile properties, where the yield strength and ultimate tensile strength are 492 and 930 MPa, similar to those of conventionally manufactured Inconel 625 alloys.