A critical assessment of fatigue crack nucleation and growth models for Ni- and Ni, Fe-based superalloys

Ni- and Ni, Fe-based superalloys are used extensively in the hot sections of gas turbines in the aerospace and power generation industries. One way to improve the performance of turbines is through increased operating temperatures and stresses. Therefore, an understanding of the factors that influence resistance of these materials to creep and fatigue is necessary to build models that can predict the lives of components in these harsh operating conditions. Predicting crack nucleation (or formation) and the subsequent rate of crack propagation is a complex problem because of the interactions between microstructure, cyclic deformation, and the high temperature effects of creep and environment; an additional influence is variable amplitude loading during the service life. This paper will discuss the pertinent research over the past three decades that has considered microstructural, temperature, environmental, frequency and loading effects on fatigue crack growth in these important intermediate temperature alloys and is divided into sections devoted to crack nucleation, short crack growth, and long crack growth.