Microstructural evolution of welded austenitic stainless steels irradiated in the spectrally-tailored ORR experiment at 400°C

Abstract

Microstructural evolution of austenitic stainless steels and their welds has been examined after spectrally-tailored neutron irradiation. JPCA and 316W, containing 0.24 and 0.08 wt% of titanium, respectively, were electron-beam welded. TEM disks taken from these weld joints were irradiated in the ORR (Oak Ridge Research Reactor), to 7.4 dpa and almost 100 appm He. Base metal specimens of 316R with very low titanium content (0.005 wt%) were also irradiated. Specimens were examined by precision immersion densitometry before TEM observation. Only the 316R base metal showed measurable swelling by density change. Cavity swelling, determined by TEM observations in the base metals, was 0.29% for 316R, 0.06% for 316W and 0.03% for JPCA. Titanium effectively suppressed the cavity swelling of the base metals. The cellular microstructure of fusion zone remained after this irradiation both in JPCA and 316W with uniform distribution of cavities. Welding did not degrade the swelling resistance as measured either by immersion densitometry or TEM.