An Accelerated Creep Testing (ACT) Program for Advanced Creep Resistant Alloys for High Temperature Fossil Energy (FE) Applications (Final Report)
The research objective of this study is to develop an accelerated creep testing (ACT) program for advanced creep resistant alloys for high temperature FE applications. This research produced a new ACT for metallic materials based on Time-Temperature-Stress Superposition (TTSSP). In TTSSP, there exists a fundamental relationship between creep resistance, time, temperature, and stress that can be manipulated to reduce test durations. In our study, the stepped isostress method was employed where step increases of load during creep testing accelerated the time-to-rupture. Well-posed constitutive models including sin-hyperbolic and Wilshire-Cano-Stewart where calibrated using the SSM data and employed to predict the conventional creep response of the material. In our best experiments, <100-hour tests on lnconel 718 at 750 deg C produced over a 64x acceleration of data when compared to conventional data from Japan's National Institute of Materials Science. The ACTs enable the rapid screening of candidate materials, where a small test matrix of short duration tests can be employed to determine the creep resistance (minimum-creep-strain-rate, stress-rupture, and creep deformation) of a material across decades.