ABSTRACT
Wire arc additive manufacturing (WAAM) is a direct energy deposition (DED) process that uses arc welding. It is a method of stacking beads made by melting metal wires with an arc heat source generated by a short-circuit current. Compared to other metal additive manufacturing methods, this process can be used to quickly produce large and complex-shaped metal parts. However, due to the multi-bead stacking method, the surface is highly curved and the dimensional errors are large; therefore, post-processing of the surface by cutting is required. Impellers, which are widely used in various industries, have complex shapes and high material consumption during cutting; therefore, the WAAM process can improve the manufacturing efficiency. In this study, a manufacturing process for an impeller with a diameter of 160 mm was developed by using the WAAM process. A 6-bladed fan-type impeller used for high-pressure fluid delivery was similarly modeled, and the product was additively manufactured using an Inconel 625 alloy wire. Manufacturing conditions that ensure productivity and quality or the product were determined through experimentation. Considering the post-processing of the WAAM-fabricated structure, the robot and tool paths of the impeller model were designed, and the error in the process coordinate system caused by attaching and detaching the workpiece between the two processes was reduced. Through the post-processing of the WAAM-fabricated structure, the production efficiency and process reliability were verified when the conventional manufacturing method and WAAM process were applied.
ABSTRACT
Several studies have been conducted to improve combat vehicle capabilities, such as the bulletproof performance of armor and fuel efficiency through weight reduction. Titanium alloys and ceramic materials are expensive and difficult to process; therefore, they can be applied only in specific locations. In addition, arc welding, which is relatively inexpensive compared with other welding processes, is widely used in industrial fields; however, because welding is often performed in multiple passes to join one part, the productivity is reduced. Therefore, in this study, mechanical properties were investigated according to production time and heat input by applying tandem pulse gas metal arc welding (GMAW) to increase productivity. The experimental data were obtained by varying the wire feeding speed. In addition, the current-voltage waveforms were measured, and the volume shift was analyzed by comparison with images captured using a high-speed camera. To analyze the mechanical properties of the tandem weld for the welding of high-hardness armor plates, the appearance (top bead and back bead), cross-section, hardness, tensile test, impact test, and spatter generation of the welded part were analyzed. The results show that all Tank-automotive and Armaments Command (TACOM) standards for the base material were met when the tandem wire feeding speed was 11 + 11 m/min, and the single-pass process increased production speed by a factor of more than 10. Tandem pulse GMAW is shown to be a viable option for improving productivity and maintaining high-quality welds for high-hardness materials.