Effect of dendrite arm spacing and the γ′ phase size on stress rupture properties of Ni₃Al-base single crystal superalloy IC6SX

Abstract

The effect of dendrite arm spacing and the size of γ′ phase on stress rupture properties of as-cast Ni₃Al-based single crystal superalloy IC6SX was studied. It has been found that the stress rupture properties were affected by dendrite arm spacing and the size of γ′ phase significantly, i.e., the stress rupture lives of as-cast specimens under the test condition of 1100°C/120 MPa were significantly increased from about 10 h to 31 h with decreasing dendrite arm spacing and the size of γ′ phase from 3.0 μm and 1.6 μm to 1.3 μm and 0.8 μm, respectively. The creep cracks generated easily in the brittle Y-NiMo phase. Then the cracks gradually mergered and grew up during creep, and finally led to specimens fracture. The orientated coarsening of γ′ phase has been found in the stress ruptured specimens, due to the elements diffusion. However, the γ′ phase did not form the integrated structure during the short periods of 10–31 h as the creep tests lasted.