Fatigue fracture mechanism and life assessment for irregular film cooling hole structures in Ni-based single crystal turbine blades

Abstract

Film cooling holes are the main cooling structures in nickel-based single-crystal cooling turbine blades. To evaluate the low-cycle fatigue life of irregular gas film holes, nine types of Ni-based single-crystal flat-plate test pieces with irregular film cooling holes of different shapes were designed in this study. Fatigue tests were performed at high temperature (850 ℃) and the multiscale fracture mechanisms of the samples analyzed in detail. The stress–strain field around the irregular film cooling holes was analyzed based on crystal plasticity theory using the finite element method. Three life prediction models based on the Coffin–Manson–Basquin formula, maximum principal strain, and crystal plasticity theory were proposed to predict the fatigue life of irregular film-cooled pore structures. The predicted results are all within the double-error band.