Fatigue behavior and fracture characteristics of 718Plus nickel-based superalloy at high temperature

The paper describes high cycle rotational bending fatigue (HCF) performance and fracture characteristics of 718Plus alloy at 600°C and 700°C, where the relationship between maximum cyclic stress (S) and fatigue cycles (N) at 600°C and 700°C is explored. We drew S-N curves, and established mathematical model, with simulating S-N curve function. The crack initiation of smooth specimens focus on the surface or subsurface, where the stress concentration caused by inclusions, carbides and microstructure defects, leading to tearing, and inclusion is the main form of crack initiation. In addition, the high cycle fatigue life of 718Plus alloy is greatly affected by the microstructure defects. According to the analysis of high cycle fatigue fracture morphology, at 700°C, the alloy fatigue crack growth is faster, and the number of secondary cracks is more than 600°C. Thus, the growth behaviour is greatly affected by temperature.