STRESS-CORROSION CRACK-GROWTH STUDIES ON AISI TYPE-316 STAINLESS-STEEL IN BOILING ACIDIFIED SODIUM-CHLORIDE SOLUTION

Stress corrosion cracking (SCC) data for AISI type 316 stainless steel in solution-annealed and sensitized (at 923 K for 20 h) conditions ar e presented in this paper. The tests were conducted in an environment of boiling 5 M NaCl + 0.15 M Na2SO4 + 2.5 ml/l HCl using a fracture me chanics approach. Stress parameters, K-I and J(I), were calculated alo ng with the crack growth rates (da/dt). The tests were conducted under both increasing stress intensity and decreasing stress intensity cond itions. The sensitized stainless steel was found to have lower values of K-ISCC and J(ISCC) and higher plateau crack growth rates than the s olution-annealed material. The value of K-I for the transition of the cracking mode from transgranular to intergranular in the sensitized st ainless steel corresponded to the value of K-I above which the plateau region started. In both conditions of the material, the initiation of stress corrosion cracking and the initial crack propagation were tran sgranular. The sensitized material exhibited a transition to an interg ranular cracking mode while the solution-annealed material did not. A large number of secondary cracks were observed in the solution-anneale d material.