Creep anisotropy of a 3rd generation nickel-base single crystal superalloy in the vicinity of [001] orientation

Abstract

The effect of orientation on the creep behavior of a 3rd generation Ni-base single crystal superalloy with orientation deviated from [001] direction 10°∼20° was studied at 1100 °C/150 MPa and 850 °C/650 MPa. It is shown that the creep anisotropy almost disappears at 1100 °C/150 MPa for samples within 20° of [001]. Rafts with waving structures are formed in all samples which eliminate the various γ/γʹ microstructures caused by orientation deviation and hinder the matrix dislocation movement in similar ways. While the creep properties are highly anisotropic at 850 °C/650 MPa. The creep lives of samples close to [001]-[011] boundary are much longer than those of samples close to [001]−[1‾11] boundary, which is mainly caused by the activated slip systems at primary creep stage. Multiple <112>{111} slips are more likely to be activated in samples close to [001]-[011] boundary, and single <112>{111} slip system dominates the deformation of samples close to [001]−[1‾11] boundary. The phenomenon is rationalized in view of the nucleation and propagation of <112>{111} slip systems by means of the nominal resolved shear stress (RSS) analysis.