Fatigue and Creep-Fatigue Behavior of Irradiated and Unirradiated Type 308 Stainless Steel Weld Metal at Elevated Temperatures

Results from elevated temperature, strain controlled fatigue tests with and without hold periods at peak tensile strain on specimens cut from Type 304 stainless steel plates welded using Type 308 stainless weld wire with controlled residual elements (CRE) are reported. Specimens were irradiated to fluences of 0.1 to 1.1 × 10²² neutrons (n)/cm², E > 0.1 MeV at 450 and 600°C, while the postirradiation test temperature was 482 and 593°C respectively. Irradiation reduced the fatigue life of the weld metal at 593°C by about one half in the low cycle region (> 5 000 cycles to fail), but cyclic life was equivalent or slightly superior to the unirradiated material in the higher cycle region (> 10 000 cycles to fail). At 482°C and at the lower fluence, the fatigue behavior of the irradiated specimens was almost equivalent in the low cycle region and superior in the high cycle region. Introducing tensile hold periods at the peak strain of each fatigue cycle of the 593°C tests resulted in reductions in the fatigue life but at a much lesser rate than the base (parent) metal. Irradiation further reduced the life of the hold time tests. Hold periods had no significant effect at 482°C. Orientation effects were seen in all weld metal tests with the parallel orientation (specimen axis parallel to the weld seam) showing a superiority in cyclic life over those taken transverse to the welding direction.