Crack growth behavior of ferritic steel for USC boilers in pressurized superheated steam

AbstractIn this study, effects of superheated steam on cyclic crack propagation behavior of a heat resistant steel were investigated. Crack propagation experiments were carried out on NF616 (9Cr-0.5Mo-2WVNb) in pressurized superheated steam (600°C/10MPa) under cyclic loading either with or without holding time at constant load. Superheated steam environment has two opposing effects on cyclic crack growth, acceleration and retardation. A modified tarnish rupture (TR) model has been proposed to explain the crack propagation behavior. The crack propagation rate estimated based on the TR-type model well agreed with the experimental data.