Liquation cracking resistance and microstructural characteristics leading to low susceptibility in borated stainless steels for neutron absorbers

Abstract

This study presents a comprehensive investigation of liquation cracking resistance in Borated Stainless Steels (BSSs) within the compositional range of ASTM A887 grade. Thermomechanical simulation was utilized to evaluate their hot cracking characteristics, providing valuable insights into the microstructural aspects. Cylindrical specimens were prepared from the three types of hot-rolled BSS sheets with varying boron content. The Gleeble simulator was employed to conduct on-heating and on-cooling hot ductility tests, specifically replicating the thermal cycles of the weld heat-affected zone, with a focus on the partially melted zone. The reduction in area was quantified as a measure of ductility, and in-depth microstructural analysis was conducted to unveil the underlying mechanisms contributing to liquation cracking susceptibility. BSSs corresponding to 304B3, B4, and B5 generally exhibited a lower brittle temperature range, and an increase in boron content was found to slightly reduce cracking susceptibility. This research clarifies the issues of low liquation cracking susceptibility in BSSs, offering valuable insights that significantly enhance their industrial performance as neutron absorbers in disposal of used nuclear fuel and nuclear power plants.