LASER-WELDING IN A HIGH-PRESSURE GAS ENVIRONMENT

A study was undertaken to investigate the effect of a high pressure ga s environment on the laser welding mechanism, This was specifically re lated to high power CO2 lasers in the power range between 1.2 and 5 kW , A small high pressure chamber rated up to 150 bar was utilized for t he trials. Successful laser welding was completed up to a pressure of 50 bar in the pressurized helium environment. The chamber was modified to incorporate a high pressure transmissive zinc selenide window and internal focusing optics, The initial welds exhibited wide and shallow profiles indicating a loss of keyhole penetration welding, By filming the welding action the problem was found to be the formation of a pla sma approximately an order of magnitude larger than in normal atmosphe ric conditions. The solution was to implement a gas jet system and to use a higher power laser. The resulting welds in terms of penetration and quality were significantly improved.