Development of New Ferritic/Martensitic Steels for Fusion Applications

Martensitic steels are considered for structural applications for fusion power plants, but they are limited by strength to operating temperatures below 550-600degC. For increased plant efficiency, steels for >650degC service are sought. Based on the science of precipitate strengthening, a thermomechanical treatment (TMT) was developed that respectively increased strength at 700degC of commercial nitrogen-containing steels and new steels designed for the TMT to 80 and 200% greater than for commercial steels with a conventional heat treatment. Precipitates in the steels after the TMT were up to eight-times smaller at a number density four orders of magnitude greater