**Experimental Investigation of the Influence of Wire Arc Additive Manufacturing on the Machinability of Titanium Parts**

#### **Unai Alonso 1,\*, Fernando Veiga 2, Alfredo Suárez 2 and Teresa Artaza 2**

1 Department of Mechanical Engineering, University of the Basque Country (UPV/EHU), 48013 Bilbao, Spain


 Received: 6 December 2019; Accepted: 20 December 2019; Published: 22 December 2019

**Abstract:** The manufacturing of titanium airframe parts involves significant machining and low buy-to-fly ratios. Production costs could be greatly reduced by the combination of an additive manufacturing (AM) process followed by a finishing machining operation. Among the different AM alternatives, wire arc additive manufacturing (WAAM) offers deposition rates of kg/h and could be the key for the production of parts of several meters economically. In this study, the influence of the manufacturing process of Ti6Al4V alloy on both its material properties and machinability is investigated. First, the mechanical properties of a workpiece obtained by WAAM were compared to those in a conventional laminated plate. Then, drilling tests were carried out in both materials. The results showed that WAAM leads to a higher hardness than laminated Ti6Al4V and satisfies the requirements of the standard in terms of mechanical properties. As a consequence, higher cutting forces, shorter chips, and lower burr height were observed for the workpieces produced by AM. Furthermore, a metallographic analysis of the chip cross-sectional area also showed that a serrated chip formation is also present during drilling of Ti6Al4V produced by WAAM. The gathered information can be used to improve the competitiveness of the manufacturing of aircraft structures in terms of production time and cost.

**Keywords:** WAAM; titanium; mechanical properties; drilling; chip geometry; cutting forces; hole quality
