Cyclic deformation, fatigue crack initiation and crack growth in a nickel-based single-crystal superalloy

Abstract

Single-crystal nickel-based superalloys are dominantly used for turbine blades due to their superior mechanical properties, fatigue and creep resistance at elevated temperature. Typically, gas turbines operate at high alternating load during engine start-up and shut-down, which subjects nickel-based superalloys to severe cyclic loads in harsh environments. For gas turbine blades, a large proportion of service life is spent in the initiation and growth of short fatigue cracks. Therefore, it is important to understand the mechanism of cyclic deformation, crack initiation and the early stage of crack propagation for reliable service-life prediction and optimal design of gas turbine systems.Cyclic deformation, fatigue crack initiation and short crack growth in nickel-based single-crystal superalloys have been studied experimentally and numerically in this thesis. Strain-controlled low-cycle fatigue (LCF) tests were carried out, with a focus on the effects of crystal orientation and temperature. [Continues.]