Effect of strain rate on the stress corrosion cracking of TP439 stainless steel in water vapor environment at 500 ℃

The effect of water vapor on the stress corrosion cracking (SCC) behavior of TP439 stainless steel at 500 °C was investigated using slow strain rate tensile tests at three strain rates of 2 × 10 –5 /s, 2 × 10 –6 /s, and 2 × 10 –7 /s. Air was selected as a comparative blank test environment for the water vapor environment. The results showed that the tensile strength of the specimens increased significantly in air when the strain rate was decreased from 2 × 10 –5 /s to 2 × 10 –7 /s, while it decreased in water vapor. Dynamic strain aging (DSA) and SCC are the main factors contributing to the difference in tensile strength of the specimens in air and water vapor. The SCC of TP439 stainless steel in water vapor at 500 °C occurs at a strain rate of 2 × 10 –7 /s or even lower. Based on the SCC susceptibility index and SEM observation of specimen fracture, TP439 stainless steel exhibits a slight transgranular SCC in water vapor with low SCC susceptibility.