Effect of Environmental Variables on the Stress Corrosion Cracking of Inconel 600 Steam Generator Tubing

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Abstract
Pressurized water reactor steam generator tubing fabricated from Inconel 600 with processing histories typical of past and current production methods has been evaluated for stress corrosion cracking susceptibility. Quantitative relationships between failure times and the various factors that affect the susceptibility are being developed. These variables include stress, strain, strain rate, environment, and temperature. Constant extension rate tests have been employed to simulate material subjected to active deformation produced by denting and to provide data on crack velocities. Reverse tube U-bend specimens provide failure time versus temperature relationships in service-related environments for determining the service life expectancy of tubing that was no longer actively denting. Constant load and cyclic load tests have also been conducted. Initial results indicate that semilog Arrhenius relationships with temperature exist in the crack propagation stage and possibly crack in the initiation stage, which may make it possible to evaluate various heats of material and heat treatments with short-term high temperature tests.