Abstract
The susceptibility of subzero treated SUS 301 stainless steel to stress corrosion cracking (SCC) was studied in boiling 35% MgCl2 solution at 200MPa. The specimens were prepared by subzero cooling to 77K for 28.8ks after 0∼45% prestraining at 195K or 373K, and they were successively SCC-tested.
The content of α'-martensite formed by subzero cooling was found to be maximum at about 5% prestrain at 373K. Above this prestrain, however, the mechanical stabilization of retained austenite occurred as a result of gradual decrease in α'-martensite content. On the other hand, the SCC susceptibility of the subzero treated specimens decreased with increasing α'-martensite content, which seems to be caused by promotion of general corrosion and thus prevention of crack initiation during SCC-tests. The transgranular fracture occurring along the {111} plane for the subzero treated specimens was characterized by the plate-like pattern. In this case, it seemed that ε-martensite contributed to the susceptible path for hydrogen cracking.
Based on the above results, the role of thermally transformed martensite during SCC of metastable austenitic stainless steel was discussed.
