Comparison of laser and electron beam welding

Electron beam and laser beam welding are very similar. Both are processes with a high beam intensity which are responsible for a deep welding effect. However, these processes employ different absorption mechanisms. The electrons, accelerated in an electron gun, lose their energy by scattering and ionisation of the material. A typical absorption length for 100 keV electrons in steel is of the order of 50 mym. The degree of absorption is more than 70%. The interaction between a laser beam and material (e.g. steel) is due to the inverse "Bremsstrahlung". Usually the degree of absorption for Co2-Lasers at metallic surfaces is less then 10%. But if the laser intensity is high enough, a laser induced plasma takes place at the interaction area. With the development of this plasma the degree of absorption will increase the nearly 100%. However, the different between laser and electron beam welding can be explained by looking at beam and plasma characteristics.