Konrad Bartkowiak, S. P. Edwardson, G. Dearden, K. G. Watkins
Laser Group, Department of Engineering, University of Liverpool, Brownlow Street.
Liverpool L69 3GH, UK
Abstract: Laser forming is an emerging technology which shows great potential for direct manufacture, prototyping and a means of alignment and distortion removal. An industry sector where its use is under consideration is aerospace, in particular for the forming of high strength aerospace alloys such as Ti-6Al-4V. This paper includes a multiple pass 2D laser forming comparative study on titanium alloy Ti-6Al-4V using two different types of Nd:YAG laser, pulsed (fibre delivered to an x-y stage) and CW (fibre delivered to a 6 axis robot). The use of Nd:YAG lasers for the laser forming of this material is being investigated as the need for absorptive coatings may be eliminated (costly and difficult to apply and remove). Key to the industrial acceptance of laser forming of this material is the development of cost-effective systems that avoid the detrimental diffusion of oxygen into the surface at elevated temperatures. To this end samples were processed in different atmospheres, in air and in argon (oxygen suppression), for the argon atmosphere two methods were investigated. The first employed a specially developed shroud delivery nozzle for the robot system. The second employed a controlled atmosphere chamber (<2ppm O2). The cumulative bend angle at a number of processing conditions was recorded and a comparison made. The effects of laser forming on the material properties of the titanium alloy were also investigated; factors studied were the depth of transformed zones, total thickness of test coupons at various number of passes, microstructures formed and the microhardness of the heated section.