Study of hybrid additive manufacturing based on pulse laser wire depositing and milling

The hybrid additive manufacturing which involves direct metal deposition and high-speed milling has been considered as an effective process to make high performance products with well surface finish. Research that have been reported indicate that continuous energy sources can lead to intolerable residual stress and distortion even after the parts are processed by machine tools. Therefore, a hybrid additive manufacturing machine tool based on pulse laser wire depositing is established taking advantage of its intensive exposure. The designed work area of the hybrid AM machine tool is 50 mm × 50 mm × 100 mm. On this basis, a set of preliminary experiments are carried out to study the performance of the proposed hybrid AM process. Both the substrate and the wire are stainless steel (SUS304), and the wire diameter is 0.6 mm. Depositing trails were kept by oxide film since shield gas is not used during the deposition. Results show that stabilization of the process has a strong impact on both the surface finish and the microstructure. Moreover, experiment results indicate that wire feeding performance is the critical factor influencing the product performance due to the small weld pool size and the rapid melting and solidifying. Typical macrodefects of the fused welding and the exclusive flaw of additive manufacturing are detected. Microstructures show that column grains less than 1 μm dominate the deposition zone, where the column grains grew in the direction of depositing on the middle layers and along the curvature direction on the top surface. A thin wall about 0.5 mm wide is milled, and the result shows that the surface of the bead is greatly improved and no defects are detected after the thin wall is cut. However, the trapezoid cross section indicates that a further study on cutting is still demanded.