Laser welding of refractory metals

Welding of thick section refractory metals is difficult with conventional a rc processes but can be accommodated with high-intensity-beam sources such as the electron or laser beam. High-laser-beam irradiance is necessary to a chieve deep penetration of refractory metals. Consequently, a focused beam of high power and beam quality is required. A 500 W diode pumped Nd:YAG was used to perform bead-on-plate tests on 2 mm sheets of rhenium and tungsten . The welds were sectioned and analyzed for profile and porosity. Results i ndicate the difficulty in using high-irradiance beams to weld rhenium and t ungsten. Microhardness measurements indicate no significant decrease in har dness in the fusion zone. However, the presence of cracks tended to produce a slight decrease in the hardness measurements. (C) 2001 Laser Institute o f America.