The Effect of Fluid Flow on the Stress Corrosion Cracking of ASTM A508 Cl 2 Steel and AISI Type 304 Stainless Steel in High Temperature Water

The susceptibility of sensitized Type 304 stainless steel and ASTM A508 Cl 2 steel to SCC in high temperature oxygenated water, as determined using constant extension rate tests, is found to depend upon the velocity of the fluid flowing past the gauge section. This work has demonstrated that in both cases, the failure time increases with increasing flow rate and that both the crack initiation time and the apparent crack propagation rate depend upon the flow velocity. The longer failure time is mainly attributed to an increase in the crack initiation time. It is suggested that the smaller crack propagation rate during the initial crack propagation period is controlled by the physical and electrochemical factors but the higher crack propagation rate results from the fact that as initiation is delayed a higher stress intensity exists at the crack tip.