Crystal Viscoplasticity Model for Creep Failure Mechanism Analysis and Fracture Life Prediction in Ni-Based Single Crystal Superalloy

Abstract

The performance of single crystal (SX) turbine blades during service is greatly affected by rafting, which increases the mean free path of dislocations, hence accelerating the rate of creep. The creep responses of the second-generation nickel-based SX superalloy were analyzed at a temperature of 980 °C and under various loads using Scanning Electron Microscopy (SEM), transmission electron microscope (TEM) and image processing software. The microstructure evolution parameter was utilized to quantitatively determine the rafting condition by quantifying the width of the matrix phase during creep, and subsequently incorporated into the constitutive model. The creep fracture life prediction model is established based on the Norton equation derived from crystal viscoplasticity theory, which characterizes anisotropy and incorporates the definition of equivalent damage to reflect the evolution of microstructure. The model provides a quantitative creep fracture analysis of service conditions by quantifying the microstructure evolution.

Keywords: single crystal superalloy, Creep, rafting, creep fracture life, crystal viscoplasticity