Optimization of the hot-wire laser additive manufacturing process

This thesis investigates the optimization of the hot wire laser additive manufacturing (HWLAM) process with a focus on Inconel 718 deposition. HWLAM is a wire-based directed energy deposition technique that combines laser power with resistive wire preheating to improve energy efficiency and deposition stability. Compared to conventional wire laser additive manufacturing (WLAM), the introduction of current as an additional process parameter significantly affects heat input, material flow, and final part quality. In this study, four key process parameters (laser power, current, scanning speed, and wire feeding speed) were systematically examined to evaluate their influence on bead geometry, overall surface quality, and microstructural characteristics. The objective of this work is to define stable process windows that enable defect-free and dimensionally accurate bead production. A mathematical model was first established to calculate the theoretical wire linear energy required for complete melting of IN718 wire. Guided by this model, a comprehensive set of experiments was performed using a robotized manufacturing cell. In total, 142 parameter sets and around 450 depositions were tested, applying both coarse and fine process mapping strategies. Each deposition was characterized in terms of bead geometry, surface quality, and process defects, while microstructural analyses provided additional insights into dilution, contact angle, and grain morphology. The results show that successful manufacturing is achieved within a process window centered around the calculated wire linear energy of 8.7 J/mm. It is observed that joule heating should be used as a supplementary source in terms of energy proportions. Introduction of joule heating as additional heat source resulted in smoother depositions. Additionally, much faster deposition rates were achieved using significantly less laser energy than with the WLAM process. This reduces both energy consumption and production time.