|Title||Creep, Fatigue, and Oxidation Interactions During High and Very High Cycle Fatigue at Elevated Temperature of Nickel-Based Single Crystal Superalloys|
|Publication Type||Conference Paper|
|Year of Publication||2020|
|Authors||Cervellon A., Yi J.Z, Corpace F., Hervier Z., Rigney J., Wright P.K, Torbet C.J, Cormier J., Jones J.W, Pollock T.M|
|Editor||Tin S, Hardy M, Clews J, Cormier J, Feng Q, Marcin J, O'Brien C, Suzuki A|
|Conference Name||Superalloys 2020|
|Keywords||Creep, fatigue, High temperature, Superalloy|
High-temperature fatigue of Ni-based single crystal superalloys is studied at 1000 °C in a wide range of loading conditions (−1 ? R ? 0.8) and number of cycles (103 − 109). Under fully reversed conditions, a competition between crack initiations from the surface— assisted by oxidation—and from internal metallurgical defects—mostly large casting pores—is observed. Increasing the testing frequency shifts the competition to a higher number of cycles. Conversely, decreasing the casting pore size or coating the specimen promotes surface initiations. When a positive mean stress is added (R ? 0), a creep deformation/damage mechanism mainly controls fatigue life, despite fracture surfaces presenting a variety of initiation types. Fatigue life can be predicted by a simple creep law if the contribution of the alternating stress is considered. A linear damage summation method that considers pure fatigue and pure creep damage is used to predict the fatigue lives, and Haigh diagrams for different alloys are presented.