Initiation and Growth of Stress Corrosion Cracks in Type 316L Stainless Steel During Slow Strain Rate Testing

The initiation and growth of cracks in type 316L (UNS S31603) stainless steel (SS) in a chloride solution containing thiosulfate ions (⁠$S2O32−$⁠) during slow strain rate testing (SSRT) were analyzed on the basis of fracture mechanics. Crack behavior on the specimen surface was observed in situ using a charge-coupled device (CCD) camera with a videotape recording system. Three types of specimens were used: a single-notched plate, a smooth cylinder, and a smooth plate. The single-notched specimen failed to produce a sharp crack similar to that formed on the smooth specimens. For the smooth specimens, the stress intensity factor (K_ISCC) was found to vary from 3.9 MN/mP^3/2 to 5.0 MN/mP^3/2, and the crack growth rate ranged from 5.2 x 10⁻⁹ m/s to 1.0 x 10⁻⁸ m/s, which approximately agreed with data determined by other authors using a fracture mechanics approach. Thus, the SSRT combined with the in situ observation technique was useful in analyzing the crack initiation and growth process.