The development of a high-chromium, nickel-base consumable-filler metal 52XL-for nuclear applications

This paper describes a filler metal development project designed to identify a Ni-30Cr consumable that exhibits resistance to both weld solidification and ductility-dip cracking, and meets the performance requirements for applications in the nuclear power industry. Initially, computational modeling and small-scale laboratory melting experiments were used to identify compositions of interest. Wires were then produced and tested using a number of weldability tests, including cast pin tear testing, transverse varestraint testing, strain-to-fracture testing, and Gleeble hot ductility testing. Based on the results, a Ni-30Cr-8Fe-4Mo-4Ta-0.03C composition (designated FM 52XL) was identified that meets the design requirements of high resistance to both solidification and ductility-dip cracking. Extensive weldability testing of this new composition conducted by the Electric Power Research Institute showed that the new filler metal has superior weldability to other high Cr, Ni-base filler metals used in the nuclear power industry including FM 52MSS (ERNiCrFe-13) and FM 52i (ERNiCrFe-15). Extensive characterization of the solidification behavior and microstructure of this new filler metal is reported here. The nominal solidification temperature range of this filler metal is 150 degrees C. It forms about 1 vol% eutectic at the end of solidification. Ductility-dip cracking resistance is developed by formation of eutectic-type gamma/TaC, which strengthens the grain boundaries by a combination of boundary tortuosity and pinning, and is effective in resisting grain boundary sliding. This work demonstrates how a combination of computational modeling, small-scale solidification tests, and laboratory weldability testing can be used to economically develop a new filler metal with specific weldability and performance requirements.

Automated summary

This paper describes a filler metal development project that successfully developed a Ni-30Cr filler metal with high resistance to both weld solidification and ductility-dip cracking. Computational modeling and laboratory tests were used to identify the desired composition, and extensive weldability testing showed that the new filler metal outperformed other high Cr, Ni-based filler metals commonly used in the nuclear power industry. The solidification behavior and microstructure of the new filler metal were also characterized in detail.