MAR-M-247 creep assessment through a modified theta projection model

Abstract

Nickel-based superalloy MAR-M-247 creep curves obtained from constant stress testing have been analyzed within a modified Evans–Wilshire θ projection approach. Model parameters have been optimized to cover a range of stresses and temperatures. Experimental range of temperatures and stresses was 150, 190, 220 and 250 MPa at 870 ∘C; 80, 100, 120 and 140 MPa at 980 ∘C; and and 50, 70, 90 and 110 MPa at 1038 ∘C. This approach predicts the onset of tertiary creep and estimates the stress rupture life under temperature/stress conditions characteristic of gas turbine components. The creep parameters for the modified approach are a function of stress and temperature and once fitted allow the creep strain to be predicted up to the onset of tertiary creep stage with an R2 accuracy of 0.85. The developed creep model is compared to a Norton–Bailey approach to demonstrate the current model’s ability to formulate a criterion capturing the onset of tertiary creep.