The effect of porosity size and oxidation on the HCF property of nickel-based single crystal superalloy at 980 °C

The high-cycle fatigue (HCF) lives and fatigue limits of nickel-based single crystal superalloys (NBSX) with different porosity sizes were investigated at 980 degrees C. The test results show that the failure cracks prone to initiate from large internal pores, and the HCF properties are mainly controlled by the critical pore size. However, when the stress is close to the fatigue limit, the secondary cracks will initiate from the oxide layer obviously, which will further weaken the HCF properties. Therefore, a life prediction model based on the critical plane parameter and oxidation kinetic equation was proposed to evaluate the effect of porosity size and oxidation on the HCF life of NBSX. Then, combing the life prediction model and Murakami model, a fatigue limit evaluation model was presented. Compared with test results, the life prediction model and fatigue limit evaluation model are accurate and effective. Finally, the defect-tolerance analysis was carried out by the Kitagawa-Takahashi diagram, which could be a visual guide for the anti-fatigue design of NBSX.

Automated summary

In this study, the high-cycle fatigue (HCF) lives and fatigue limits of nickel-based single crystal superalloys (NBSX) with different porosity sizes were investigated. It was found that the critical pore size plays a crucial role in determining the HCF properties. Additionally, the initiation of secondary cracks from the oxide layer was observed, which further weakens the HCF properties. A life prediction model based on the critical plane parameter and oxidation kinetic equation was proposed to evaluate the effect of porosity size and oxidation on the HCF life of NBSX. Furthermore, a fatigue limit evaluation model combining the life prediction model and Murakami model was presented. The accuracy and effectiveness of the models were verified through comparison with test results. Lastly, the defect-tolerance analysis using the Kitagawa-Takahashi diagram provided valuable insights for anti-fatigue design of NBSX.