FACTORS AFFECTING THE ENVIRONMENTAL ASSISTED CRACKING BEHAVIOR OF 2205 DUPLEX STAINLESS STEEL

The reliable performance of duplex stainless steels (DSSs) in chloride- and sulfide-containing solutions is important to many industrial processes. Previous studies have shown that DSSs are susceptible to environmental assisted cracking (EAC) under certain conditions in these solutions; however, the mechanical and electrochemical conditions under which DSSs may become susceptible are not well understood. To elucidate some of these mechanical and electrochemical conditions, the EAC susceptibilities of a 2205 DSS were evaluated in an acidic-chloride solution and a sulfide-containing caustic solution. Low frequency cyclic tests were performed for a fixed number of cycles, and the crack initiation events were examined after these tests. In the chloride solution, corrosion pits are the preferential sites for crack initiation under cyclic loading. In the sulfide-containing caustic solution, precipitates tend to be the preferential sites for cracks to initiate, especially the ones at or near the interface of the phase boundary and grain boundary. Hydrogen embrittlement (HE) was also found to be a potential form of EAC in this solution at room temperature when a cathodic potential (CP) was applied.