| Abstract Scope |
Ferritic/martensitic FeCrAl steels are one of the most promising candidate materials for advanced nuclear energy systems, particularly those operating at much higher temperatures and harsher environments than the current light water reactors. This is due to FeCrAl excellent thermal properties and dimensional stability. In modern nanostructured ferritic alloys, refined grain and oxide particle sizes significantly contribute to the radiation tolerance in fast reactor applications. Consequently, techniques such as laser beam welding and electron-beam welding are preferred due to their narrow heat affected zones.
Laser welding of Kanthal APMT FeCrAl alloy was conducted using a high-power multi-process laser welding system. To study the feasibility of laser beam welding, various single-sided laser weld techniques were tested. A simple fixture was applied to control thermal distortion during the welding process. Post-weld heating at 300 °C was applied to reduce crack formation. The effects of laser power and welding travel speed on the weldability of FeCrAl alloys were investigated. Microstructure of the welds were analyzed using optical microscope, scanning electron microscope, and transmission electron microscope.
The results prove that laser beam welding of Kanthal APMT FeCrAl alloy is feasible. The welding tests demonstrate that high-quality welds can be achieved using optimized laser welding parameters together with post-weld heating. Microstructural characterization indicates the formation of welding cracks is associated with thermal stress during laser welding due to large cooling rates and aluminum segregation. By releasing the constraint in the thickness direction of the sample and integrating a post-weld heating process, cracking can be successfully restricted. |