An Analysis of Primary Creep of Nickel-Base Superalloy Single Crystals

Abstract

The orientation and stress dependence of the primary creep rate in single crystals of a nickel-base superalloy is predicted from crystallographic deformation mechanisms. An experimentally determined relationship between the deformation rate and applied stress is employed to calculate the independent contributions of each of the possible slip systems to the strain rate. Calculations were made for single crystals of a nickel-base superalloy tested in tensile creep at 1400 deg F, at which temperature the active slip planes are known to be {111}, and the slip directions either 〈110〉 or 〈112〉 at high or low strain rates, respectively. Comparison with measured primary creep rates showed the 〈110〉 contribution to be negligible and that while semi-quantitative agreement with the 〈112〉 analysis was obtained, an accurate prediction of creep rates may require inclusion of strain hardening in the analysis.