The stress rupture behavior of nickel-base single crystal superalloys is a primary issue facing aero-engine design, which has been studied for more than 40 years. To a large degree, it is the existence of film cooling holes with the introduction of air cooling techniques that adds the extra challenge to the problem. Using both experimental and numerical methods, we explore here the stress rupture behavior of nickel base single crystal plate specimens subject to multi-row film cooling holes. As the numerical simulation part, finite element analysis using Abaqus was performed. Numerical results reveal that the existence of film-holes causes stress concentration and transforms local stress from uniaxial to multi-axial. For the stress distribution of different types of specimens, we defined a stress multiaxiality factor to quantitatively characterize the degree of the stress complexity and examined its effect on the rupture behaviors of the specimens along with the true stress concentration factor. The test was also carried out and results indicated that the creep rupture lives of one- and two-row specimens turn out to be longer than those of non-hole specimen. However, the three- and four-row configuration showed the opposite trend. Among the geometric parameters of film-hole configuration, film-hole row spacing is a predominant one influencing the creep rupture properties. Numerical results agree well with the fracture positions and shapes of specimens.

The isothermal oxidation behavior of single crystal DD6 film-cooling blades was investigated. The isothermal oxidation tests were conducted at 1050 °C, and the phase analysis was performed by XRD, while SEM (EDS) was employed to observe the material. In addition to experimental studies, a numerical simulation using three-dimensional finite element analysis based on Abaqus software (Version 6.13) was implemented to model the growth stress in specimens during the isothermal test. The obtained results showed that the average oxidation rate of specimens rose with increments in film hole spacing, up to a maximum value at a film hole spacing of 0.75 mm, and then fell, which could be interpreted with the concepts of the oxidation-affected zone and the growth stress. The results obtained from the numerical simulation of the growth stress agreed with the experimental results of the average oxidation rate. The oxide scale of film-cooling specimens mainly consisted of three layers, the NiO outer layer, the spinel sublayer containing cracks, and the non-continuous thin Al₂O₃ inner layer. The surface of the oxide scale commonly underwent spallation of the NiO outer layer, and the exposed sublayer could grow new NiO particles. The size of the NiO particles on the edge of the film holes was larger than those on the walls of the film holes. SEM images clearly showed that electro-hydraulic beam drilling on DD6 superalloy specimens could erode the γ phase in the γ/γ′ two-phase matrix, thereby inducing damages in regions near film holes.