Effect of Secondary Orientation on Thermal Fatigue Behavior of a Nickel-base Single Crystal Superalloy DD33

Abstract

The effect of secondary orientation on thermal fatigue behavior of a third generation nickelbased single crystal superalloy DD33 was investigated. Samples with different secondary orientations were machined along(100) and(110) plane, respectively, and thermal fatigue test was performed cyclicly between room temperature and 1100 oC. It was found that different initiation sites and propagation orientations of the thermal fatigue cracks were observed in samples with different secondary orientations. In samples with secondary orientation of [100], thermal cracks initiated at the edge of the holes along a direction with 45 oincline to the directional solidification(DS) direction and propagated along also the derection with 45 oincline to the DS direction. While in samples with secondary orientation of [110], thermal cracks initiated at the edge of the holes vertical to the DS direction and propagated along the DS direction. In general, samples with secondary orientation of [100] exhibited better thermal fatigue properties than that of [110] samples.