Non-Isothermal In-Reactor Creep of Nickel Alloys Inconel 706 and PE-16

The results of in-reactor step temperature change experiments conducted on two nickel alloys, PE-16 and Inconel 706, were evaluated to determine the creep behavior under non-isothermal conditions. The effect of the temperature changes was found to differ significantly between the two alloys. Following a step temperature change, the creep rate of PE-16 adjusted to the rate found in isothermal tests at the new temperature. In contrast, for Inconel 706, a reduction in irradiation temperature from 540 to 425°C produced a 300% increase in creep above that measured at 540°C in isothermal tests. The Inconel 706 in-reactor creep response to temperature changes was attributed to the dissolution of the γ″ phase and the subsequent loss of precipitation strengthening at temperatures below 500°C.