Modelling the uniaxial creep anisotropy of nickel base single crystal superalloys CMSX-4 and RR2000 at 1023 K using a slip system based finite element approach

The significant creep anisotropy associated with crystallographic orientation in single crystal Ni-base superalloys in the temperature range 1023–1123 K has been well documented over the past 20 years. The mechanisms primarily responsible for this anisotropy are established and are related to proximity to symmetry boundaries and the rotation that occurs during creep in single slip orientations. However, quantification and modelling of this behaviour has not been sufficiently addressed. It is not yet possible to determine the effect of lower temperature anisotropy and transient behaviour in macroscopic models and component analysis. In this paper this situation is addressed through the development of a mechanism based slip system model capable of accounting for the major effects associated with lower temperature anisotropy, including transient behaviour and rupture life. The model has been fitted to the first and second-generation single crystal superalloys RR2000 and CMSX-4. The results of creep and rupture tests on these alloys in many crystallographic orientations at 1023 K are presented.