Thermo-mechanical modelling of the wire arc based additively manufactured Inconel 625 superalloy

Abstract

In the as-printed state, additive manufacture of Inconel 625 employing the cold metal transfer (CMT)-wire arc additive manufacturing (WAAM) technique presents various issues due to complex residual stress. The residual stress may cause cracks and build failures. The residual stress evolution of Inconel 625 alloy was studied using Finite Element (FE) thermo-mechanical simulation implemented in Abaqus software. Residual strains and distortion in WAAM parts are two major impediments to the widespread adoption of this technology. Understanding the thermomechanical behaviour caused by the CMT-WAAM method is still a difficult task that must account for the influence of both process and material factors. Eleven beads on plate trial were carried out on Inconel 625 substrate for the process parameter optimization for wire feed rate of 12 m/min and constant torch speed of 650 mm/min. A sound welded 12 root pass additive bead layers with lateral overlap of 1/3 of bead width is fabricated at an optimum value of heat input per unit length (Q)=200.97j/mm. A complex thermal history with several reheating and cooling peaks is clearly demonstrated with the help of the proposed numerical model. Validation of the proposed numerical model is obtained with thermocouple data obtained experimentally. The predicted residual tensile stresses upon removing the clamps clearly shows that the stresses are reduced by 50% when compared with the residual stress distributions with the clamps still holding the base plate. Validation of the proposed numerical model is obtained with thermocouple data obtained experimentally. It has been found that the distortion profile shows quadratic type of variation within the deposited bead and linear type variation along the edge of the substrate.