Elevated temperature fatigue crack growth in directionally solidified GTD-111 superalloy

GTD-111 is a General Electric proprietary nickel-base superalloy widely employed in a growing fleet of industrial gas turbines. However, much of the published research to date has focused on creep damage and coating durability, with no available data on fatigue crack growth rate (FCGR). Accordingly, FCGR has been measured at several load ratios and an elevated temperature, 760 degrees C (1400 degrees F) corresponding to typical turbine bucket conditions. In order to account for load ratio effect, several different methods for determining Walker model parameters are discussed in terms of methodological consistency and accuracy.