Laser Beam Welding of Titanium and Nickel Based Super-Alloys in Sub-Atmospheric Pressure

The Laser welding process is increasingly being considered for joining Titanium and Nickel based super-alloys for aerospace components. Recent advancement in solid state laser technology, such as high power Fiber and Disk lasers, has resulted in large improvements over conventional CO₂ and lamp pumped Nd:YAG laser technology in term of beam quality, electrical efficiency, power scalability, reliability and lifetime. One advantage of using lasers for welding in a vacuum is that only the component to be welded needs to be enclosed in a vacuum chamber, whilst the laser beam delivery optics can be mounted outside the vacuum chamber. The laser beam is then transmitted into this small vacuum chamber by use of a transparent window mounted in the top of the vacuum chamber. This paper describes laser welding trials on 0.250” thick coupons of the alloys Ti6Al4V and Inconel 718. A small vacuum chamber was built, and a sub-atmospheric pressure of around 0.07 mm Hg could be achieved, which is similar to that of industrial Electron beam welding vacuum chambers. The paper also describes a comparison between laser beam welding in atmospheric and sub-atmospheric pressure.