Plates of unoxidized copper and 304 stainless steel were successfully butt welded to each other using a continuous wave CO2 laser with argon, helium and air as cover gases. The position of the laser beam with respect to the joint interface and the type of cover gas used were determined to be important factors affecting weld quality. It was very important to have the laser beam exactly at the interface in order to produce acceptable welds.
The welds made with compressed air and ambient air as the cover gas exhibited excessive porosity whereas argon as the cover gas yielded welds with cracks. The helium welds were found to be crack free and did not show pores.
Microstructural evaluation of the weld was carried out with the help of an electron microprobe analyzer. It revealed considerable interdiffusion of copper into the stainless steel fusion zone and the components of the steel into the copper zone. Copper rich particles were also observed in the stainless steel fusion zone and iron rich zones were observed in the copper region, probably as a result of non-equilibrium phase transformations associated with the laser welding process.