3D printing of large-scale components of titanium alloys under open atmosphere

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Titanium alloys are light in weight and exhibit high strength and toughness, even at high temperatures. Thus, they are widely used in key sectors, such as automotive, offshore, medical and especially aerospace industry. The most widely used titanium alloy is Ti6Al4V. It accounts worldwide for more than 50% of all titanium usage, of which more than 80% is used in aerospace (Alcisto et al., 2011; Donachie, 2000; Majumdar and Manna, 2012; Dragolich and DiMatteo, 1994). Ti6Al4V can be 3D printed with laser radiation with both the LPBF (laser powder bed fusion) and the DED (directed energy deposition) process, but still now, there is the necessity of a process chamber filled with inert gas in order to prevent oxidation. The main limitations of using a process chamber are the limited ability to produce large scale parts and the high energy and resource consumption, e.g. inert gases. In this work, we demonstrate 3D printing of large-scale and oxidation-free components out of Ti6Al4V under open atmosphere conditions with DED by using local gas shielding. Large-scale parts with neither bonding defects nor cracks and a porosity lower than 0.1% are achieved. The printed material shows tensile strength of up to approx. 1270 MPa and yield strength of up to 1170 MPa, which are significantly higher than the relevant specifications. For demonstrating the technology, a pylon bracket of about half-a-meter in length for mounting the turbojet engine to the wing of an airplane has been printed. We anticipate our assay to be a starting point for 3D printing materials susceptible to oxidation under open atmosphere in the future.