Creep characterization of a Ni-based Hastelloy-X alloy by using theta projection method

The θ projection method was applied to characterize the creep behavior of the Hastelloy-X alloy at 950 °C. Four θ parameters were established by a nonlinear least square fitting (NLSF) to the creep curves. In the NLSF of the full creep curves, the θ1 and θ2 parameters were not defined with a large error, but the θ3 and θ4 parameters were defined well without an error. An optimum cutoff strain range for defining the four θ parameters was found to be a 3% strain. Four θ parameters revealed a good linearity as a function of stress. The predicted minimum creep rate showed a good agreement with the experimental data. At 950 °C of the Hastelloy-X alloy, the creep curves, the creep rate, and the time to reach a limiting strain were estimated with a wide range of stresses.