Fiber laser welding of dissimilar metal combinations for fuel irradiation capsule fabrication

Abstract

This study was carried out to obtain sound welds and to select a most suitable binary metal joint among three different dissimilar binary metal combinations such as zirconium to tantalum material, molybdenum to tantalum, and titanium to tantalum joints for the instrumented nuclear fuel irradiation testing using fiber laser welding process. To do this, metallography and micro-focus X-radiography method was employed to optimize the experimental data. From the weld bead appearance, penetration depth and bead width as well as weld defects standpoint, zirconium to tantalum joint is suggested for the circumferential joining between a seal tube and a sensor sheath. The optimized welding parameters based on zirconium to tantalum joint are suggested as well. This work was carried out to obtain the optimum welding parameters and to select a most suitable dissimilar metal combination for joining of seal tube to temperature sensor in the fuel irradiation testing. Fiber laser welding system with 150W pulsed and 50 ㎛ SI optical fiber transmission was set up to weld between the instrumented seal tube and the temperature sensor for the fuel irradiation testing. A joint of dissimilar binary metal combination of zirconium to tantalum was selected for seal tube to sensor joining in terms of penetration and sound welds, in which welding parameters optimized by metallography and micro-focus X-radiography method were employed. The laser power was found to have the most dominant effect on the welds among welding parameters used in this experiment.