Environmentally Controlled Crack Growth Rate of AISI 304 Stainless Steel in High Temperature Sulfate Solutions

The intergranular crack (IGC) growth rate of furnace-sensitized AISI 304 stainless steel (SS) in a 0.01M Na₂SO₄ solution at 250 C has been measured using modified wedge opening loading (WOL) specimens loaded under constant displacement conditions at various applied potentials. It was found that the propagation of cracks occurs at potentials above −0.3 V_SHE and that the crack growth rate increases with increasing potential. The critical potential for cracking is very close to that reported previously in the same environment for tests performed under constant straining conditions and under cyclic loading at low frequencies. The crack growth rate also depends on the value of the stress intensity factor (⁠K_I⁠) for K_I values lower than 20 to 25 MPa⋅m^1/2, but it is almost independent of K_I at higher K_I values. Crack growth rates were also measured on welded and post-weld heat treated specimens. An internal instrumented bolt (IIB) was found to be a reliable device for measuring crack growth rates in high temperature, high pressure aqueous environments.