Statistical modelling and optimisation of WAAM-CMT parameters for enhanced tensile strength of ERNiCr-3 nickel-based superalloy

This study investigates the influence of current (130–150 A), welding speed (180–300 mm/min), and interlayer cooling time (30–90 s) on the ultimate tensile strength of ERNiCr-3 nickel-based superalloy fabricated via cold metal transfer-based wire arc additive manufacturing (WAAM-CMT). A three-factor, five-level central composite design with response surface methodology was employed, comprising 20 experimental runs. Horizontal tensile specimens were extracted from multi-layer builds and tested. Analysis of variance revealed that interlayer cooling time is the most significant parameter (p = 0.0002), followed by quadratic effects of current and welding speed. A quadratic regression model was developed (R² = 0.9642), validated by normal probability and correlation plots. Optimal parameters (140.574 A, 239.311 mm/min, 66.391 s) yielded a maximum ultimate tensile strength (UTS) of 592.205 MPa. Microstructural characterisation using OM, SEM, and EDS showed that optimal conditions produce a defect-free cellular-dendritic microstructure with fine secondary dendrite arm spacing and discontinuous elemental segregation. Fractography confirmed ductile-dominated failure. This work provides a statistically validated empirical model for predicting UTS of WAAM-CMT ERNiCr-3 deposits.