Cyclic deformation behaviors and damage mechanisms in P92 steel under creep-fatigue loading: Effects of hold condition and oxidation

P92 steel has gained plenty of attention as a top contender for steam generator components and main steam tubes due to the growing need to increase the energy conversion efficiency. However, a major contributor to the premature failure of these components remains the interaction of creep and fatigue damage caused by typical dwell fatigue loading conditions. In this study, creep-fatigue tests of P92 steel were conducted under strain-controlled cyclic loading including hold durations up to 3600s at 873K in air. Special attention was given to the influence of hold conditions and oxidation on cyclic deformation and damage mechanisms. The results revealed that introducing hold time substantially decreased the failure life, with compressive hold causing more severe damage than tensile hold. Additionally, oxidation became severer with longer hold time, resulting in increased surface roughness, crack initiation sites and density of secondary cracks. Fatigue dominated the failure in the case of the short-term tensile hold, and the interaction of creep, fatigue and oxidation dominated the failure in long-term tensile hold tests. In contrast, the failure in compressive hold case was dominated by fatigue and severe oxidation. Furthermore, a three-dimensional oxidation-creep-fatigue damage interaction diagram was proposed for quantitative assessments in practice.