Stress corrosion cracking tests for low carbon stainless steels with work hardened layer

To avoid introduction of Cr depletion at grain boundaries by welding process, low carbon stainless steels (SSs) were used in corrosive environment as one of countermeasures for Stress Corrosion Cracking (SCC). Recently, it is reported that SCCs were introduced at portion with work hardened layer although low carbon SSs had been used at core shrouds and primary loop recirculation piping in Boiling Water Reactors. To simulate and examine the phenomenon, mechanical working, metallographic observation, hardness test and SCC tests in chloride solutions were conducted for low carbon SSs. From the results of metallographic observation and hardness test, it was confirmed that slip bands were observed around the surface and hardened layer was introduced by mechanical working. From the results of SCC tests, it was noticed that cracks which introduced from the surface, had grown into the matrix. It is thought that low carbon SSs with work hardened layer have susceptibility to SCC from the above. (author)