Characterization of Damage Induced by Impacting Objects in Udimet-500 Alloy

Foreign object damage (FOD) is one of the common mechanisms in turbine blade failures which reduces high cycle fatigue life and contributes significantly to premature failure. Therefore, this study experimentally simulated FOD on the first stage blade of a gas turbine. Foreign objects with two parameters of object nose shape (spherical, conical, and flat) and impact angle (90° and 45° relative to the blade surface) were impacted on the surface of flat specimens of Udimet-500 at a temperature of 733°C with velocity of 300 m/s (same as working condition of blades). In order to evaluate the impact site morphologies, induced craters were first studied by scanning electron microscopy (SEM). Then samples were sectioned symmetrically, and by using image analysis tool software, the depth of each crater was measured. Finally, based on the results, it was found that maximum and minimum stress concentration factors and induced microcracks, respectively, are regarding to flat projectiles with impact angel of 45° and spherical at impact angle of 90°.