Environment assisted cracking of 308L weld metal in high temperature water

Abstract

• The environmental enhancement factor of 308 L weld metal reached a value of 50 when the frequency was decreased to 0.00001 Hz. • The 308 L weld metal showed excellent SCC resistance regardless of the thermal aging or water chemistry. • No preference of the γ/δ crack path and no elevated EAC either with thermal aging or in oxidizing water was attributed to the no sensitization of the γ/δ boundaries before and after thermal aging. The environment assisted cracking (EAC) behavior, including stress corrosion cracking (SCC) and corrosion fatigue (CF), of a low carbon 308 L stainless steel weld metal was evaluated in high temperature water. The effects of thermal aging (400 °C for 10,000 h) on the crack growth rate (CGR) are discussed. Experimental results reveal an environmental acceleration effect on CGRs with decreasing loading frequency, and the environmental enhancement factor reached a value of 50 when the frequency was decreased to 0.00001 Hz. The 308 L weld metal showed excellent SCC resistance regardless of the thermal aging or water chemistry, which is related to the low carbon content and well-controlled duplex microstructure. After thermal aging, the ferrite/austenite (γ/δ) phase boundaries show negligible sensitization, consistent with the low carbon concentration. No preference of the γ/δ crack path and no elevated EAC either with thermal aging or in oxidizing water was attributed to the no sensitization of the γ/δ boundaries before and after thermal aging.