Irradiated microstructure of alloy 800H

Austenitic alloy 800H has the same basic composition as INCOLOY alloy 800 (Fe–20Cr–32Ni) but with significantly higher creep-rupture strength due to a required 60 μm minimum grain size. It is one of the high temperature candidate alloys being considered for Generation IV nuclear reactor systems. The radiation resistance of 800H has not been previously studied. This work provides information on the microstructural changes in 800H after irradiation using 5.0 MeV Ni ions at 500 °C to 5 and 50 dpa. Following irradiation, changes in microstructure and phase stability were studied using transmission electron microscopy (TEM). At a dose of 50 dpa, no voids were found and the density and size of the faulted loops were measured to be 2.3 × 1016 cm−3 and 8.4 nm, respectively. There are fine precipitates distributed in 800H with an average size approximately 6 nm and a density greater than 9.1 × 1015 cm−3. The high Ni content and the presence of precipitates are believed to be responsible for the resistance to void formation at dose up to 50 dpa.