Abstract
With the increasing challenge of extending the service life of structural steels components subjected to high-temperature environments, there is an urgent need to investigate the mechanisms of creep-fatigue and to develop new steels that can effectively withstand these complex loading regimes. This study examines the creep-fatigue behavior of a novel 310 NbN austenitic stainless steel, enhanced with nitrogen and niobium, under high-temperature conditions. Specimens were subjected to tests at 675 °C with varying hold-times of 0, 5, 60, and 600 s. Results indicated that longer hold times significantly increased crack growth rates and reduced cycles to fracture, highlighting a time-dependent crack propagation. Fracture surface analysis revealed a shift from transgranular to intergranular fracture with longer hold-times, indicating predominant creep damage. Predictive models, including the strip-yield model, aligned well with experimental data, emphasizing the critical role of hold-time in designing high-temperature steel components for improved durability.