Fiber laser welding characteristics of commercially pure zirconium (R60702) and structure-mechanics-corrosion performances of the joint

Zirconium and its alloys are mainly applied in the nuclear industries due to the small absorption cross section of thermal neutron, good mechanical performances, and favorable corrosion resistance. Fiber laser bead-on-plate welding of 1.12-mm thick commercially pure zirconium (R60702) plate was studied in this paper. Weld width ratio R_w was taken to evaluate the effects of primary welding parameters on weld morphologies. It was found that the value of R_w should be higher than 0.8 to prevent the pore defect, and lower than 0.95 to avoid the concave crater. And then welding experiments based on quadratic regression orthogonal design were conducted to figure out the relationship between R_w and primary welding parameters. With the increasing of laser power, the maximum R_w was shifted along the direction of more positive defocusing distance or higher welding speed. Afterwards, the microstructure, mechanical properties, and electrochemical corrosion resistance of welded joint and base metal were studied. And most importantly, the corrosion resistance of fiber laser welded joint was qualitatively better than that of base metal in 20% (volume fraction) acetic acid solution, owing to the martensitic transformation occurred in fusion zone (FZ) and heat affected zone (HAZ).