关键词: 镍基单晶合金, 气膜孔, 飞秒激光, 初始制造损伤, 裂纹扩展

Abstract: Nickel-based single crystal turbine blades are usually arranged with hundreds of film-cooling holes with a diameter of 0.2-0.8mm. The existence of film-cooling holes destroys the structural integrity of turbine blades, and becomes a fre-quent part of blade failure and fracture under high temperature fatigue load. Therefore, the fatigue fracture study of the nickel-based single crystal film-cooling hole specimen fabricated by femtosecond laser was carried out to solve the strong relation between the initial manufacturing damage of film-cooling holes and the fatigue fracture behavior. Firstly, a three-dimensional spiral hole-making simulation model was established by hydrodynamic method to obtain the hole shape evolution law in the hole-making process; Subsequently, the surface integrity of the filming-cooling hole was analyzed from three aspects: geometry, microstructure and mechanical properties, the taper of the air film pore was 0.19°, the depth of the thermal damage zone at the pore edge was about 18 μm and severe oxidation, and the maxi-mum residual stress at the pore edge was 463MPa; Afterwards, the fracture of the 980°C fatigue crack propagation test found that the crack originated in the heat-affected zone of the hole wall and propagated in a direction perpen-dicular to the load in a counterclockwise rotation of about 6° in an approximately elliptical profile. Finally, an M-integral crack propagation driving force model based on the theory of incremental plasticity and conformational force is pro-posed, and an effective function description model of the relationship between the fatigue crack propagation rate and the effective crack propagation driving force of air film pore is constructed on this basis.

Key words: nickel-based single crystal alloys, film-cooling hole, femtosecond lasers, initial manufacturing damage, crack propagation