Design of low-Ni martensitic steels with novel cryogenic impact toughness exceeding 190 J

This study aimed to develop steels with reasonable material costs to replace Fe-9Ni (wt.%) steel, which is suitable for cryogenic applications. To this end, a newly designed Fe-2Mn-5Ni-0.1C steel was treated by quenching-tempering (QT) and quenching-lamellarizing-tempering (QLT); subsequently, the microstructural evolutions and resultant impact absorbed energy were systematically investigated. At -196 degrees C, the QLT-processed steel exhibited a higher impact absorbed energy (similar to 193 J) than the QT-processed steel (similar to 168 J), and it was similar to that of Fe-9Ni steel. The excellent impact absorbed energy of the QLT-processed sample was attributed to the high damage tolerance afforded by the active transformation-induced plasticity from the retained austenite and the pronounced plastic deformation of the soft martensitic matrix due to double-step tempering.

Automated summary

This study aimed to develop cost-effective steels for cryogenic applications by investigating the microstructural evolutions and impact absorbed energy of a newly designed Fe-2Mn-5Ni-0.1C steel treated with quenching-tempering (QT) and quenching-lamellarizing-tempering (QLT) processes. The QLT-processed steel exhibited a higher impact absorbed energy than the QT-processed steel and Fe-9Ni steel at -196 degrees C, thanks to the active transformation-induced plasticity from retained austenite and pronounced plastic deformation of the soft martensitic matrix due to double-step tempering.