Analysis of fracture and cracks of single crystal blades in aero-engine

An aero-engine failed during testing. It was found that a gas-cooled single crystal turbine blade had fractured and several other blades had cracked. In order to find out the failure mode and cause, fracture surface observation, metallurgical structure examination and surface trace observation were carried out, and the stress state of the blades during service was analyzed by finite element method (FEM). The results show that the failure mode of the blades is fatigue fracture caused by excessive stress. friction traces can be found at the end of the blades, and the microstructures of the blades are normal. The failure of the blades was mainly caused by two factors. On one hand, cracks initiated at the stress concentration zone, where greater working stress existed. On the other hand, there existed friction between the blade tips and the outer shell, which added an alternate stress to the stress concentration zone. Based on the analysis above, the transient round angle at the stress concentration zone should be increased, and the gap between the blade tips and the outer shell should be adjusted to avoid friction, so that the reliability of the blades can be improved.