ANISOTROPY IN MULTIAXIAL CREEP OF NICKEL-BASED SINGLE-CRYSTAL SUPERALLOY CMSX-2 - (EXPERIMENTS AND IDENTIFICATION OF ACTIVE SLIP SYSTEMS)

Combined tension-torsion creep tests of a nickel-based single-crystal superalloy CMSX-2 are performed at 900-degrees-C under stationary as well as nonstationary stress conditions using thin-walled tubular specimens with the crystal direction [001] oriented in the axial direction. Marked effects of anisotropy are observed both on the magnitude of creep rate and on the noncoaxiality between creep rate and stress. To identify operative slip systems in the present creep tests, the experimental data of steady-state creep are analyzed on the basis of a crystal creep theory of the power-law type. It is shown that the experiments are simulated well if we assume simultaneous operation of the {111} [112] octahedral and {100} [110] cubic slip systems.