Thermal fatigue failure mechanism of thin-walled Ni₃Al-based single crystal alloy with film cooling hole

The refined structure design of the single crystal (SX) turbine blades through the thin-walled coupled film cooling hole (FCH) improves the cooling efficiency. Frequent take-off and landing cycles of aircraft create a build-up of thermal stresses that can lead to thermal fatigue cracks around FCHs of thin-walled turbine blades. Due to the lack of systematic research on the thermal fatigue behavior around FCH of thin-walled SX turbine blades, a Ni₃Al-based SX with high temperature-bearing capacity was selected in this study, and the effects of peak temperature, wall thickness and hole diameter on the thermal fatigue behavior of SX were studied by designing L9(3³) orthogonal experiments and finite element method (FEM). The key findings reveal that wall thickness has the most significant impact on thermal crack growth, followed by peak temperature and hole diameter. Three types of thermal cracks were primarily identified: top/bottom thermal cracks caused by longitudinal temperature gradient during the quenching stage, oblique thermal cracks resulting from the activation of the octahedral slip system, and structural thermal cracks due to machining defects. This study provides a reference and data support for the structural design of single crystal turbine blades for a new generation of aero engines.