Surface Crack Growth Behavior of Structural Metals in High Temperature Water Environments

This paper reports on a study of surface crack growth of two nuclear structural steels, SA333 Gr6 carbon steel used for piping and SA533 Grade B pressure vessel steel, both tested under cyclic loads in 288°C (550°F), 0.2 ppm oxygen water at 10.34 MPa (1500 psi). Results are compared with tests on compact type (CT) specimen geometries tested in similar environments. It was found that, for the frequencies employed, the crack growth rates for the two specimen geometries were not widely different, despite the high net mean stresses employed in the surface crack geometries. However, substantial differences were noted in the crack velocity response under static loading for the two geometries, suggesting that such differences can be expected in low frequency loading more typical of service conditions, raising questions about the applicability of CT geometry test results for the materials, temperatures and environments used in this study. Temperature effects, air environments and R-value effects for surface crack geometries are also reported.