Stress corrosion crack growth in type 316 stainless steel in Supercritical water

A crack growth rate test on a compact tension specimen of Type 316 (UNS S31600) stainless steel was conducted in pure water under both subcritical and supercritical conditions. The crack growth rate during the test was measured using the reversed direct current potential drop technique. Under subcritical conditions, crack growth increased between 288 degrees C and 360 degrees C by a factor of 2. Shifting the water condition from subcritical to supercritical at 400 degrees C significantly reduced the stress corrosion crack growth rate. The crack growth rate was further suppressed by temperature increases to 450 degrees C and 500 degrees C under supercritical conditions. In addition, the effect of dissolved oxygen was to lower the crack growth rate compared to the deaerated case. The drop in crack growth rate with temperature is hypothesized to be due to crack blunting caused by rapid oxidation.