Thermomechanical fatigue of round tube specimens manufactured by precision directional solidification casting method

In the present study, a superalloy round tube specimen prepared by directional precision casting without mechanical turning is experimentally investigated under the thermomechanical fatigue conditions of the in-phase and out-of-phase thermomechanical angels from 500 degrees C to 1000 degrees C. The deformation behavior and damage mechanism of the round tube specimens under TMF load are discussed. It was confirmed that the tension-compression asymmetry under TMF cycling is affected by temperature-load phasing and mechanical strain range. Moreover, the damage to round tube specimens includes creep, fatigue and oxidation. Due to the concentrated stress, the rough surface of the specimen provides suitable locations for crack initiation. A novel life prediction approach that combines the Neu-Sehitoglu model and modified Manson-Coffin model was proposed in response to the traditional life model's insufficient prediction performance. This method may explain the TMF life of precision cast specimens.