抄録
SCC resistance of nickel-base alloy, Alloy 600, in high temperature pressurized water environments was evaluated by the cyclic crack growth tests of high stress ratio.
Three kinds of materials with different heat treatments namely annealed, sensitized and thermally treated alloys were tested and it was found that the effect of enviroment on the fatigue crack propagation rate became remarkable under a high stress ratio (R) and that sensitized and annealed materials showed higher crack growth rates compared to the thermally treated one.
The fracture mode of the materials tested was intergranular when the effect of environment on the fatigue crack growth rate was observed. From these results the effect of environments can be considered to be caused by SCC. Cyclic KISCC values evaluated made clear that the thermally treated material gave a higher KISCC. value compared to the annealed and sensitized materials.
With the high stress ratio cyclic crack growth test in the environment, the SCC resistance of nickel base alloy can be estimated quantitatively within a short period which is less than a fifteenth of the time that is required for the normal double U-bend test.
