Martensitic creep-resistant P92 steel was deformed by different methods of severe plastic deformation such as rotation swaging, high-pressure sliding, and high-pressure torsion at room temperature. These methods imposed significantly different equivalent plastic strains of about 1-30. It was found that rotation swaging led to formation of heterogeneous microstructures with elongated grains where low-angle grain boundaries predominated. Other methods led to formation of ultrafine-grained (UFG) microstructures with high frequency of high-angle grain boundaries. Constant load tensile creep tests at 873 K and initial stresses in the range of 50 to 300 MPa revealed that the specimens processed by rotation swaging exhibited one order of magnitude lower minimum creep rate compared to standard P92 steel. By contrast, UFG P92 steel is significantly softer than standard P92 steel, but differences in their strengths decrease with increasing stress. Microstructural results suggest that creep behavior of P92 steel processed by severe plastic deformation is influenced by the frequency of high-angle grain boundaries and dynamic grain coarsening during creep.

Department of Materials Science Institute 1 University of Erlangen Nuremberg D 91058 Erlangen Germany

Department of Materials Science Kyushu Institute of Technology Kitakyushu 804 8550 Japan

Faculty of Materials Science and Technology Technical University of Ostrava 17 Listopadu 15 708 00 Ostrava Czech Republic

Institute of Physics of Materials Academy of Sciences of the Czech Republic Zizkova 22 616 62 Brno Czech Republic

Magnesium Research Center Kumamoto University Kumamoto 860 8555 Japan

Synchrotron Light Application Center Saga University Saga 840 8502 Japan

Technology Department Nagano Forging Co Ltd Nagano 381 0003 Japan

UJP PRAHA a s 156 10 Praha Zbraslav Czech Republic

World Premier International Research Initiative International Institute for Carbon Neutral Energy Research Kyushu University Fukuoka 819 0395 Japan

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