Evaluation of different drilling quality and fatigue life prediction of nickel-based superalloy using equivalent initial flaw size

The initial quality assessment and total fatigue life prediction of film cooling holes under different drilling processes have great impact on key structural components. In this paper, the initial fatigue quality of nickel-based superalloys with different drilling processes were evaluated and the fatigue life was predicted based on the equivalent initial flaw size (EIFS) theory. We raised the modified K-T diagram method based on intrinsic stress intensity factor threshold considering the small crack data. The fatigue crack growth test at room temperature is carried out on the single edge notched specimens made of nickel-based superalloy GH4169 under two different drilling processes (HEDM and FEDM) to quantitatively evaluate EIFS values. Then, a new expression of fatigue crack growth rate is proposed based on EIFS. Finally, the total fatigue life within 2 times error band is predicted by combining EIFS and fatigue crack growth rate, which confirms the validity of fatigue models and tests.