Low cycle fatigue fracture mechanism of a modeling specimen with cooling film hole of DD6 single crystal superalloy

The flat plate specimens of nickel-base single crystal superalloy DD6 with different numbers of laser-processed cooling film holes were used to study the low cycle fatigue properties at 900℃. The test data and SEM fracture images were analyzed. The results show that the life of single-hole specimens is ten times of that of the close-spaced holes specimens in the same experimental condition. A number of microcracks are found around the cooling film hole and the destruction of the specimens with cooling film holes is a typical multi-source rupture. The cracks propagate along the {001} planes for single-hole specimens and the middle holes of the close-spaced holes specimens, but the cracks extend along a plurality of slip plane for up and bottom holes of the specimens with close-spaced holes.