Authors:
Jonathan Blackburn
Laser Processing Research Centre, The University of Manchester, Manchester M60 1QD, United Kingdom

Chris Allen
Paul Hilton
TWI Ltd., Granta Park, Abington, Cambridge CB21 6AL, United Kingdom

Lin Li
Laser Processing Research Centre, The University of Manchester, Manchester M60 1QD, United Kingdom

The increasing utilization of titanium alloys in the aerospace industry, a direct result of socioeconomic pressures, has created the need for a production process which can produce high quality near-net-shape titanium alloy components. Keyhole laser welding is a joining technology which could be utilized for this requirement. In general, when laser welding titanium alloys, a jet of inert gas, directed at the region of the laser beam/material interaction point is utilized to achieve the weld quality required. A statistical study has been performed in order to determine the optimum position and flow rate of this directed gas jet, with respect to reducing the weld metal porosity and optimizing the weld profile, for autogeneous Nd:YAG laser welding of 3.25 mm thickness Ti-2.5Cu and Ti-6Al-4V. As a result, butt welds have been reproducibly made with a quality that exceeds the most stringent aerospace weld quality criteria. High speed imaging and spectroscopic analysis of the welding process have revealed that, when correctly set-up, the directed inert gas jet disperses the formation of excited metal vapor above the keyhole and also significantly changes the hydrodynamic behavior of the weld pool.