Combined effect of secondary dendrite orientation and wall thickness on creep behavior of a Ni-base single crystal superalloy

The combined effect of secondary dendrite orientation and wall thickness on the creep properties of a single crystal superalloy at 1100 °C/140 MPa was studied. Both the secondary dendrite orientation and wall thickness exhibit great effect on the creep rupture life of thin wall samples. Creep rupture life decreases with the decrease of wall thickness from 1.5 mm to 0.5 mm, while more obvious decrease was observed in < 100 > samples than that of < 110 > samples. For sample with wall thickness of 0.5 mm, almost no difference could be detected between the two groups of samples with different secondary dendrite orientations. The average creep life of < 110 > samples is a slightly higher than < 100 > samples in the present experiment. While longer creep rupture life was obtained in < 100 > samples when the wall thickness was 1 mm and 1.5 mm. It was discussed based on the decrease of effective load-bearing cross section by oxidation, deformation by slip, and also the interaction of dislocation with sample surface.