Effect of complex stress states on creep rupture life of nickel-based superalloys: Mechanisms and modeling

•Creep tests on smooth and single-hole plates were conducted to explore the effect of complex stress state on creep life.•A viscoplastic model was developed to simulate creep behavior of single-hole plates and V-notched bars.•A mechanical explanation for significant differences in creep life among differently structured specimens was provided.•New life model accounting for stress triaxiality accurately predicts creep life of single-hole plates and V-notched bars. This study investigates the effects of complex stress states on creep rupture life of nickel-based superalloys. Creep experiments were conducted at 900 °C on both smooth and single-hole plate specimens. A viscoplastic constitutive model was developed to simulate the creep behavior of single-hole plates and V-notched bars. The analysis offered a detailed mechanical explanation for the significant differences in creep rupture life observed among these differently structured specimens. This investigation incorporated the effects of complex stress states into the Monkman-Grant relationship, resulting in a new creep life model that accounts for stress triaxiality. The results indicate that the increased stress triaxiality significantly extends the creep life of V-notched bars. In contrast, the single-hole plates, which approach a uniaxial stress state, exhibit a creep rupture life closely aligning with that of the standard smooth plates. The proposed model accurately predicts the creep rupture life of both single-hole plates and V-notched bars, with all predictions falling within a threefold scatter band.