PWSCC susceptibility of cast stainless steel and nickel based alloy of dissimilar metal butt welds

Constant load tests for estimating the crack growth rate at the initiation stage and slow strain rate tests for PWSCC susceptibility and activation energy estimation were carried out using a specimen with dissimilar metal butt welds in simulated PWR primary water to evaluate the PWSCC susceptibility of nickel based alloy of dissimilar metal butt welds (welding cast stainless steel and alloy 600 using the 82 and 132 alloys) used in pressurized water reactors. No clear differences in activation energy and crack growth rate at the initiation stage were observed between the 82 and 132 alloys. Higher PWSCC susceptibility was observed in the 132 alloy than 82 alloys. Crack growth rates at the initiation stage of dissimilar metal butt welds were several times lower than that of alloy 600 matching metal welds. These results might suggest that dissimilar metal butt welds do not adversely affect the PWSCC crack growth rate at the initiation stage. The crack depth of dissimilar metal butt welds at the 290degC part was evaluated from the activation energy and crack growth rate at the initiation stage and crack depth of dissimilar metal butt welds at the 320degC part. As a result, it was concluded that the dissimilar metal butt welds at the 290degC part still remained at the initiation stage. (author)