Thermal fatigue behavior of low activation ferrite-martensite steels

Components like test blankets of the thermonuclear fusion reactor ITER or like DEMO-blankets are subjected during service to alternating thermal and mechanical stresses as a consequence of the pulsed reactor operation. Of particular concern is the fatigue endurance of reduced activation ferrite-martensite steels like the Japanese F82H mod. and the German OPTIFER IV, compared to martensitic steel for the next European torus (MANET TI), as reference material, under cyclic strains and stresses produced by typical temperature changes. Into self developed thermal cycling fatigue test rigs variable strain rates are applied to these materials, due to the constant heating rate and variable temperature changes. Thermal fatigue behavior of ferrite-martensite MANET II, including dwell times, will be reported. On the other hand F82H mod. as well as OPTIFER IV samples are thermal cyclically tested in different as received conditions and the the results are compared to those of MANET II samples after the three-step reference annealing. (C) 1998 Elsevier Science B.V. All rights reserved.