Multi-layer additive manufacturing on nickel-based superalloy by optimization of pulsed mode process parameters of single-layer bead geometry

Abstract

Recent advancements in the wire arc additive manufacturing (WAAM) process for nickel-based superalloys have had a substantial impact on metal additive manufacturing industries such as aerospace, energy, and construction. The input process parameters influence the WAAM part's dimensional accuracy, process stability, and other critical impacts. The quality of each weld layers in WAAM can be controlled by various process parameters. In this study, a single-layer bead was deposited from Hastelloy C-22 using the pulsed mode gas tungsten arc welding (PC-GTAW) process. The chosen input process parameters include pulse frequency (X1), peak current (X2), and pulse on time (X3). The design of experiments (DoE) statistical quality tool was used to optimize the parameters, and the response surface m`ethodology (RSM) technique was used to develop the design matrix. The experiments were conducted based on central composite design (CCD), and their resulting responses bead width (Y1), height (Y2), and depth of penetration (Y3) were evaluated using optical microscopy. The results of the geometrical analysis have revealed a significant correlation between the characteristics of the layer and the parameters of the process. The analysis of variance (ANOVA) method was employed to verify the validity of the actual and predicted models. The model was experimentally validated using the established optimal process parameters, and the mechanical and metallurgical performance was evaluated. The microstructure of the single-layer exhibits equiaxed, cellular, and columnar structures at various regions. The pulse mode process was found to effectively reduce elemental segregation, improve the microstructure, and enhance the mechanical properties of the weld layer. The multi-layer experiments were carried out using the optimal process parameters of a single layer. According to metallographic investigations, the multi-layer that has been deposited exhibits a lack of cracks and porosity. This study provides new insights into the stabilized properties necessary to achieve optimal process parameters and metallurgical characteristics in the robust wire arc additive manufacturing of Hastelloy C-22.