Combination of laser keyhole and conduction welding: Dissimilar laser welding of niobium and Ti-6Al-4V

• With a single laser pulse, melting ratio of Ti-6Al-4V is 8 times greater than Nb.
• In laser welding of Ti-6Al-4V/Nb conduction and keyhole modes occur simultaneously.
• In pulsed laser welding of Ti-6Al-4V/Nb keyhole forms 0.92 ms after pulse start.
• A circular melt pool forms on niobium while it’s shape is elliptical in Ti-6Al-4V.
• HSI shows Ti-6Al-4V melt pool does not freeze while Nb solidifies between pulses.

Pulsed Nd:YAG laser welding of pure niobium plate to titanium alloy Ti-6Al-4V sheet in butt joint is studied regarding the laser/metal interaction modes. To obtain the optimized process parameters in dissimilar welding of Ti-6Al-4V/Nb, the melting ratio of laser beam energy for each weld counterpart is evaluated experimentally. Different laser welding modes of keyhole and conduction are predicted regarding the absorbed energy from the similar laser pulses on each weld counterpart. Laser keyhole and conduction welding were observed simultaneously through direct visualization of laser interaction with dissimilar metals using High Speed Imaging (HSI) system.