Constitutive modeling and computational analysis of creep behavior in single crystal nickel based superalloys

In gas turbine technology, higher efficiency, in association with a reduction of carbon dioxide emission, can be obtained increasing the turbine operative temperature which in turn challenges the durability of the rotating turbine blades. Today, single crystal nickel based superalloys (SX) are the most advanced candidate material for these applications. These classes of superalloys poses a number of issues for what concerns constitutive modeling and its use in the design-by-analysis procedures. In this work a creep model for SX class of materials, obtained in the framework of dislocation mechanics, is presented and applied to CMSX-4 superalloy. In particular, the attention has been focused in modeling the material response in the temperature and stress range for which a pseudo primary creep is observed as a result of the activation of the secondary octahedral slip systems. The projectability of the model predictive capability, relatively to the minimum creep rate, over a wide range of stress and temperature and along [001] and [111], is shown. The proposed creep model has been generalized to the multiaxial state of stress following the approach proposed by MacLacklan et al. 4) and implemented into the commercial finite element model MSC.MARC and used to simulate creep response in samples and components.