Effect of long service on the fine structure of the surface of gas turbine engine rotor blades

Abstract

1. The most significant structural changes are concentrated in a thin surface layer, which is related to the character of distribution of thermal loads under conditions of the corrosive action of the medium. 2. Structural damages accumulating during service have a two-stage character: a) the removal of microdistortions and an increase in the dimensions of the blocks as a result of the removal of mechanical work hardening in the surface layer of new blades (the density of defects decreases); b) disintegration of the elements of the substructure back to dimensions smaller than in the original conditions; the microdistortions remain insignificant (lines become broader). The effect observed is caused by an increase in the boundary density of dislocations. 3. The similarity of the structural changes in different zones of the trailing edge of the blade in the last stages of service and the two-stage character of the change in fatigue strength is an indication of the difficulty of simulating long-term failure of heterophase alloys by short-term tests.