Investigation on high temperature fatigue-oxidation behavior of Ni-based single crystal with film cooling holes considering arrangement effect

The fatigue-oxidation behavior of Ni-based single crystal with film cooling holes (FCHs) fabricated by femtosecond laser was investigated considering arrangement effect. Low cycle fatigue tests were conducted under 900 °C/713 MPa and 1000 °C/500 MPa. The experimental results show that fatigue lifetime reduced as the temperature increased at equal proportional stress. And, the specimens with square penetration pattern have an average fatigue life that is higher than the specimens with triangle penetration pattern at the same condition. Then, the crack propagation modes are characterized on the fracture path, and the fatigue failure mechanism is revealed by analyzing the fracture morphology. The microstructure evolution around the FCHs shows that the fatigue crack nucleation is caused by the coupling effect of fatigue and oxidation. According to the damage mechanism, a new fatigue-oxidation coupling damage model is proposed based on crystal plastic theory. The calculation results using crystal plasticity finite element method (CPFEM) considering coupling damage show that the maximum resolved shear stress (RSS) of the FCHs triangular arrangement is higher than that of quadrilateral arrangement at the same condition. Finally, fatigue life is predicted based on coupling damage accumulation, and the results show that the accuracy of life prediction is within 2 times data dispersion band.