A new approach for welding under hyperbaric conditions can be the application of laser beams. Welding experiments have been performed with CO2 and Nd:YAG lasers at elevated pressures. Deep penetration welding with CO2 laser radiation (λ = 10,6 ∼) is not possible at elevated pressure, since the appearing metal vapor plume shields the surface. The results of trials done with a Nd:YAG laser (λ = 1,06) show that it is possible to perform deep penetration welding up to an overpressure of 2 to 3 bar today. At higher pressures heat conduction welding can be performed. This pressure level can be extended by influencing the metal vapor plume. Nd:YAG laser radiation can be transmitted through optical fibers and therefore easily be guided below sea level. This has led to the development of a mobile Nd:YAG laser system which consists of a containerized Nd:YAG laser source, a fiber for beam transmission and a working head which is capable to be remotely controlled and operated at a pressure of up to 10 bar.
Laser beam welding is now an established technology for joining metallic materials. Some advantages in comparison to conventional thermal joining technologies are a low heat input and therefore low distortion and a smaller heat affected zone, high processing speeds and an automated process. These benefits may potentially be utilized for welding in hyperbaric conditions. The two mainly used laser sources for industrial applications are the CO2 and the Nd:YAG laser. Only with these types of lasers output powers in the multi kW region can be provided which are necessary to achieve reasonable results concerning penetration depth and welding speed.
For laser beam welding the beam is focused with a lens or a mirror optic onto the surface of the material.
