A nonlinear kinetic rate model for unifying fatigue crack growth rates of nickel-based superalloys at room and elevated temperatures

Abstract

This study presents a nonlinear kinetic rate model to describe the temperature-dependence of fatigue crack growth rate (FCGR) of nickel-based superalloys across a wide range (20 to 650 °C). FCGR testing was performed using compact tension specimens of GH4742 superalloy. Metallography analysis on crack growth paths of two tested specimens suggests there is a local resistance to pure model I cracking at 20 °C, which can greatly be weakened at 650 °C. Compared to the classical Arrhenius equation, the proposed model captures the nonlinear temperature-dependence, and yields more accurate results by reducing the scatter factor from 5 to 3.