Wire-arc directed energy deposition with in situ molten-bead rolling for stable high-speed fabrication

The application of wire-arc directed energy deposition (DED) for the fabrication of large-scale metallic components has been steadily expanding. However, the process is limited by the melting and solidification behavior of the molten pool, making it difficult to maintain consistent bead height and width under high-speed deposition conditions. To address this limitation, a high-precision and high-speed roller-integrated wire-arc DED (RIWA-DED) process is proposed, in which the deposited bead is directly compressed by a roller within the liquidus–solidus temperature range in the peripheral region of the arc heat source. A compact roller module mounted directly on the welding torch was developed to induce real-time mechanical deformation prior to complete solidification, enabling precise control of bead geometry without the need for external pressing equipment. High-speed imaging and load analysis were conducted to elucidate the interaction mechanism between the roller and the molten pool and to analyze the pressurization behavior according to major process parameters. The results show that roller compression effectively stabilizes molten pool behavior, thereby suppressing bead humping and reducing surface waviness in the deposited layers. To verify the mechanical reliability of the process, the microstructure, hardness variation, and tensile properties of deposited structures with and without roller compression were compared. Under optimized conditions, multilayer deposition experiments successfully fabricated a turbine blade structure with a height of approximately 120 mm consisting of more than 90 layers, demonstrating improved surface quality and reduced geometric irregularities. In addition, the RIWA-DED process enabled high-speed deposition while significantly reducing surface waviness and minimizing the machining allowance required for post-processing. These results demonstrate that the RIWA-DED process provides a practical solution for large-scale metal additive manufacturing by simultaneously improving geometric accuracy and deposition efficiency while reducing post-processing requirements.