Effect of rafted microstructure and its temperature dependency on fatigue crack propagation in a single‐crystal Ni‐base superalloy
Motoki Sakaguchi, Ryota Okamoto, Takanori Karato, Kenta Suzuki
Abstract
Abstract Effects of rafted microstructure and its temperature dependency on fatigue crack propagation (FCP) in a single‐crystal Ni‐base superalloy are experimentally investigated. FCP tests are conducted at room temperature, 450°C, and 700°C for two types of pre‐rafted specimens, and their FCP behaviors are compared with that of a specimen with cuboidal γ′ precipitates. It is found in the experiments that there is no significant influence of rafted microstructures on FCP rate at room temperature, while a clear influence is pronounced at 450 and 700°C depending on the coarsening direction of rafted microstructures and the level of stress intensity factor range. The temperature dependency in the effect of rafted microstructure is discussed with special considerations on the microscopic FCP behavior affected by the morphology of γ′ precipitates, the coherency of the γ/γ′ interface, and temperature‐dependent slip characteristics of γ and γ′ phases.