# Wire Arc Additive and High-Temperature Subtractive Manufacturing of Ti-6 Al-4V
## 4 High-Temperature Cutting of the Titanium Alloy Object Built by WAAM
### Effect of Tool Wear Progression on Cutting Force  
We demonstrated that the initial cutting force could be reduced by about 23% when the heating temperature was 300 \({}^{\circ}\)C compared to room temperature. We then milled the Ti-6 Al-4V fabricated object at 300 \({}^{\circ}\)C using IH and investigated the changes in tool wear and cutting force as the cutting distance progressed. The heating temperature was set to 300 \({}^{\circ}\)C and compared with the case at room temperature. The fabricated object was first heated to about 500 \({}^{\circ}\)C, and then cooled to 300 \({}^{\circ}\)C before the cutting was conducted. A  
Figure 12: Cutting force transition affected by the heating temperature. (**a**) R.T.; (**b**) 50 \({}^{\circ}\)C; (**c**) 100 \({}^{\circ}\)C; (**d**) 150 \({}^{\circ}\)C; (**e**) 200 \({}^{\circ}\)C; (**f**) 250 \({}^{\circ}\)C; (**g**) 300 \({}^{\circ}\)C.  
Figure 13: Effect of workpiece temperature on cutting force of WAM Ti-6 Al-4V. total of nine paths were performed, and tool wear and cutting force were measured at the third, sixth, and ninth paths. When the feed rate was 0.15 mm/tooth, the cutting length after three passes was about 14 m; at six passes, about 28 m; and at nine passes about 42 m. We alternated the feed direction, and the center of the tool was located on the left side of the workpiece. Then the milling was performed on the down-cut side, where the chipping of the tool is suppressed. Figure 14 presents one example of an image captured by the thermal camera (FLIR, T650 sc). With the camera, we were able to measure the temperature distribution and the maximum temperature in the frame. The maximum temperature near the tool edge was considered the cutting temperature. The spatial resolution of the thermal camera was 0.68 mrad. The cutting temperature was 158 \({}^{\circ}\)C on the third pass, 179 \({}^{\circ}\)C on the sixth pass, and 187 \({}^{\circ}\)C on the ninth pass when the workpiece temperature was room temperature. When heated to 300 \({}^{\circ}\)C, the cutting temperature was 530 \({}^{\circ}\)C on the third pass, 538 \({}^{\circ}\)C on the sixth pass, and 581 \({}^{\circ}\)C on the ninth pass. Figure 15 shows the transition of the cutting force of each pass. The light blue indicates the cutting force when milling at room temperature, and the orange represents the cutting force at 300 \({}^{\circ}\)C. Even when the number of cutting passes increased, the cutting force did not increase much. However, the cutting force at room temperature was around 900 N, smaller than at 300 \({}^{\circ}\)C when the cutting force was around 1000 N.  
Figures 16 and 17 show the flank wear width during milling at room temperature and 300 \({}^{\circ}\)C, respectively. There is no photograph for the 6 th pass at 300 \({}^{\circ}\)C, because the whole view was not recorded. When milling at room temperature, the flank wear width increased to 0.33 mm, 0.46 mm, and 0.65 mm in steps of three passes. In contrast, it increased to  
Figure 14: Example of the thermal image during the milling. Figure 15: Transition of cutting force of the fabricated object at 300 \({}^{\circ}\)C and room temperature. (**a**) Third pass; (**b**) Sixth pass; (**c**) Ninth pass. 0.63 mm, 0.72 mm, and 0.87 mm when the workpiece was heated to 300 \({}^{\circ}\)C. Wear width was larger during high-temperature milling in all paths. Figures 18 and 19 show enlarged tool flanks on the third and ninth paths at room temperature and 300 \({}^{\circ}\)C, respectively. Only the boundary wear grew during room-temperature milling, but both boundary and flank wear increased during high-temperature milling. It should be noted that tool wear at 300 \({}^{\circ}\)C was almost comparable to the case after the ninth pass at room temperature.