Mechanical characterization of craters induced by impacting foreign objects on Inconel718

In this study, foreign object damage on aircraft high pressure compressor blades made of Inconel718 nickel-based superalloy was experimentally simulated at the working temperatures of the blades. Steel balls (as a foreign objects) with velocities of 292, 208, 133 m/s were impacted on the surface of Inconel718 flat specimens at various temperatures (400, 475, 550, and 625℃). In order to characterize induced craters, impact sites were studied by scanning electron microscopy to identify mechanical features such as microcracks and notches. Then, the specimens were 3D scanned to measure the depth of each crater. It was found that variation of stress concentration factors and induced damages (including microcracks and notches, loss of material, and shear bands) could occur as a result of steel ball impact with velocities of 292 and 133 m/s at temperatures of 625 and 400℃, respectively.