Anisotropic Creep Rupture Properties of a Nickel-base Single Crystal Superalloy at High Temperature

The creep rupture properties of a single crystal superalloy were tested at 975℃/255 MPa as a function of the deviation degrees from [001].The misorientation of the specimens away from [001] distributed approximately along a line between [001]-[011] and [001]-[111] boundaries in the triangle of the stereographic projection.Creep rupture lifetimes of the specimens were not sensitive to the misorientation until the deviation degree exceeded ～30 deg.Two steps of lattice rotation were found in all specimens during creep,first towards the [001]-[111] boundary,and then to [001] or [111] along the boundary.Single slip and strong asymmetric deformation were observed during the first stage of lattice rotation in specimens with large misorientation.The rotation mechanism was associated with the activated slip systems according to the calculated Schmid factors.The impact of lattice rotation on the rupture properties was also discussed.