Crack initiation mechanisms for low cycle fatigue of type 316Ti stainless steel in high temperature water

Low cycle fatigue (LCF) tests were performed for a type 316Ti stainless steel (SS) in high temperature water. Fatigue crack initiation behaviors in high temperature water were investigated. It was found that there existed several kinds of Ti-bearing precipitates, consisting of isolated TiN or duplex (Al, Mg)O/TiN, Mo-rich (Ti, Mo)C and Ti(N,C) in the steel. Fatigue cracks were mainly initiated at Ti-bearing precipitates, phase boundaries of austenite/α-ferrite phases and persistent slip bands (PSBs) in austenite. It is believed that synergism between the mechanical factors and electrochemical reactions played a key role in the process of fatigue crack initiation in high temperature water. Related fatigue crack initiation mechanisms for the 316Ti SS are discussed.