Analysis of microstructure and mechanical properties of micro-plasma arc-welding-based additive manufacturing

Wire arc additive manufacturing (WAAM) is an emerging additive manufacturing (AM) process that gained considerable interest due to its high deposition rate and flexibility in build scales. Low heat input, reduced thermal gradient, refined grains structure and optimal molten pool are required in producing more high-quality WAAM parts. Integrating a micro-plasma arc welding (MPAW) system with less or equal to 20A current is a significant consideration in WAAM technology to improve its quality. This study fabricated a single-pass multilayer structure with MPAW-based WAAM, and the effect on macro-microstructure and tensile strength has been thoroughly investigated. The results show that excessive heat at the end of layer deposition leads to deteriorated structure and irregular geometrical shapes. Owing to the WAAM process that experiences repeated heating and cooling, the bottom structure has the highest tensile strength and microhardness due to the fine dimple structure form. The observed microstructure shows that the grain size at the top wall is larger than that at the bottom due to more rapid cooling at the bottom. Based on the study outcome, the study provides a better understanding of the morphological, microstructure, and mechanical properties of samples fabricated using MPAW-based WAAM process.