Life assessment of multiaxial thermomechanical fatigue of a nickel-based superalloy Inconel 718

Recent investigations revealed significant differences of thermomechanical fatigue from isothermal fatigue. Quantifying effects of thermomechanical loads in fatigue life assessment is still an open issue. In the present work, extensive experiments are performed for a popular nickel-based superalloy under both isothermal and thermomechanical loading conditions to quantify the influence of varying temperature and multiaxial mechanical loads. Various multiaxial fatigue life models show significant deviations and cannot describe the thermomechanical fatigue life. Based on the experiments and failure analysis a new thermomechanical fatigue model is introduced to assess non-proportional thermomechanical loads and can calibrate thermomechanical multiaxial fatigue reasonably.