Influence of pulsed current GTAW-WAAM process parameters on the single layer bead geometry and multi bead multi-layer deposition of a nickel-based superalloy

Abstract

Wire + arc additive manufacturing (WAAM) is a state-of-the-art and highly efficient technique utilized to produce near net-shaped products on a large scale, employing a layer-by-layer approach. This research used pulsed current mode welding for single-layer bead-on-plate experiments to optimise the process parameters for WAAM of Hastelloy C-276. The effect of process parameters including pulsed current, pulsed frequency, and pulse duty cycle was systematically investigated on the weld appearance, depth of penetration, layer width, and layer height. The optimisation of single layer experimental runs was conducted using Box-Behnken designs (BBD) and the response surface method to construct several regression models. An analysis of variance was employed to validate the accuracy of both the measured and generated models. The BBD results indicate that interactions have a more significant impact on the peak current parameter than the resulting impact of pulse duty cycle and frequency. Validation tests were performed on the model with the optimal process variables that were identified, and its mechanical and metallurgical properties were analysed. Macrostructure and microstructural analysis of the single layer showed that the specified process parameters led to acceptable base metal fusion and bead is free from cracking. There was a considerable decrease in elemental segregation while using the pulse mode technique. Finer grain structure and reduced microsegregation enhance the hardness. Further residual stress (RS) at weld bead and base plate was 213 MPa and -240 MPa. Nonhomogeneous heat transfer during welding affects RS compressive and tensile characteristics. WAAM printing quality requires precise control of LH, LW, and DOP. This research aimed to propose suitable parameter values for manufacturing WAAM component for usage in chemical processing, nuclear, marine, and industrial settings by using unique pulsing features.