Fatigue short crack propagation behavior of selective laser melted Inconel 718 alloy by in-situ SEM study: Influence of orientation and temperature

The influence of orientation and temperature on fatigue short crack propagation behavior of Inconel 718 alloy was studied at both 25 degrees C and 650 degrees C by in-situ fatigue testing under scanning electron microscope. The fatigue crack growth rates (FCGR) showed evident dependence on orientation at both temperatures, following: XZ < X < Z. The FCGR difference of XZ and Z orientation became less pronounced at 650 degrees C. Fatigue cracks exhibited commonly transgranular fracture at both temperatures, with enhanced FCGR at 650 degrees C. Microstructurally short crack propagation showed evident fluctuations, which were closely related to the blocking effects of grain boundaries.