Investigations on the fracture behavior of Inconel 718 superalloys obtained from cast and additive manufacturing processes

This paper examines the effects of manufacturing processes on the fracture behavior of Inconel 718 alloy at room temperature. This comparative study was conducted on specimens obtained from cast and PBF (Power Bed Fusion) additive manufacturing. Mechanical testing was conducted on single edge notch specimens in bending. In order to quantify the influence of the manufacturing process on the fracture behavior, the J-R curves were obtained from the energy per unit of fracture surface area needed to drive crack growth in agreement with the ASTM standard E1820-01. Depending on the specimen type and the location of the initial notch with respect to the lasing planes, crack initiation significantly differs resulting from specific microstructures. These differences may explain why AM specimens have much higher fracture toughness at initiation (about 70-100%) and subsequent crack propagation. The in situ crack propagation was studied via the observations of the crack path along with the mechanical loading. An original picture analysis was developed to monitor the crack growth based on the location of the crack tip at specimen surface.