Research on Creep–Fatigue Interaction and Constitutive Model of Micro Sampling of Superalloy Blades

Due to the complexity and harshness of the operating environment of gas turbines, the turbine blade (the key component) faces various challenges, including high temperature, high rotational speed, and corrosive environments, which are exacerbated by stress concentrations induced at geometrical discontinuities in the blade body. In this paper, the performance of in situ sampling (notched small specimen) of nickel-based high-temperature alloy MAR-XXX blades under conditions of creep–fatigue interaction was investigated. Two types of notched small specimens, which have the same stress concentration factor but feature different geometric structures, were designed. The effects of geometry on the number of fatigue cycles (NC) of the notched specimens were evaluated through high-temperature creep–fatigue interaction tests. NC and failure mechanisms of the two types of notched specimens are clarified. A coupled damage viscoplastic constitutive model is used to simulate the test results. The simulation results align with the cracking locations observed in the tests, and the proposed cumulative damage value accurately reflects the relationship in NC between the two types of notched specimens.