ESSC & DUPLEX 2019

In numerous branches ferritic-martensitic steels are operated close to their application limits today. The advancement of thermal power generation efficiency for example was governed for decades by the further development of the ferritic-martensitic (FM) 9 - 12 Cr steel grades, which enabled a rise of appr. 120 °C in live steam temperature over a period of 60 years, but stagnates since the introduction of grade 92 in the 1990s. Since then all attempts to combine sufficient creep strength and increased steam oxidation resistance in new FM steels at temperatures beyond 620 °C failed. Furthermore the German “Energiewende” poses a lot of new challenges for structural high temperature materials, because operation modes change from mainly base load to flexible residual load compensation operation. Another example of such limitation are martensitic hot-working die steels applied for example in the production of automotive chassis parts from high strength TRIP and TWIP steels. The durability of such martensitic stamping tools is strongly limited because of both lacking mechanical long-term strength and oxidation resistance at temperatures exceeding 620 °C. These limitations are due to the conflict of complete martensitic transformation only being possible as long as the level of chromium is suitably low (< 12 wt.-%), while oxidation resistance beyond 620 °C necessitates Cr contents higher than 15 wt.-%. Low cost carbide / nitride strengthened martensitic steels thus seem to hit hard technological limits and alternatives are strongly desired. This paper describes the scientific background and technological properties of a new family of Laves phase strengthened, **Hi**gh **per**formance **Fer**ritic (HiperFer) stainless steels, under development at Forschungszentrum Jülich, Germany and designed for highest resistance against thermomechanical fatigue, fatigue crack propagation and creep as well as aqueous corrosion and steam oxidation. Microstructure, especially the role of plastic deformation for material strength, mechanical properties and application potentials will be addressed in detail.